The Influence of Negative Emotions on Prospective Memory - CiteSeerX

INTERNATIONAL JOURNAL OF COMPUTATIONAL COGNITION (HTTP://WWW.IJCC.US), VOL. 4, NO. 1, MARCH 2006

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The Influence of Negative Emotions on Prospective Memory: A Review and New Data (Invited Paper) Matthias Kliegel and Theodor Jäger

Abstract— The persuasive cognitive ability to encode, store, and execute intended actions, such as remembering to keep appointments or to pick up the kids from school after work, is termed prospective memory. In the present paper, we provide a review over the currently available studies that were interested in how the ability to prospectively remember is subject to emotional influences, such as fluctuations in mood, enduring (negative) emotional states, or clinically relevant affective disorders. The general finding is that negative emotional states and inner-states of anxiety or depression seem to interfere with the ability to execute intended actions, although the direction of this relationship seems to reverse under certain circumstances. In addition, we present novel data from a recent study that further investigated how specific negative emotions (i.e., anxiety and depression) are correlated with performance in different prospective memory tasks. Additionally, the multifaceted pattern of findings on how emotions might influence the execution of different types of intended actions in the laboratory and in everyday life is discussed. Finally, we provide some avenues for future research investigating the connection between cognition and emotion within the realm of c 2006 Yang’s Scientific Research prospective memory. Copyright ° Institute, LLC. All rights reserved. Index Terms— Prospective memory, emotion, mood.

I. I NTRODUCTION : W HAT IS P ROSPECTIVE M EMORY ? HE MEMORY system is one of the issues most extensively studied by researchers interested in human cognitive processes. Within this realm, most of the scholarly studies were concerned with the remembering of information or events from the past, which is termed retrospective remembering or retrospective memory (e.g., Baddeley, 1990). By contrast, only a relatively small number of studies have addressed another kind of memory ability, namely the ability to plan and remember to execute activities in the future. This distinct form of memory processes is referred to as prospective remembering or prospective memory (see Brandimonte, Einstein, & McDaniel, 1996; Kliegel, McDaniel, & Einstein, in press). Importantly, carrying out a prospective memory task consists of several phases, which involve distinct cognitive processes (see e.g.,

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Manuscript received December 12, 2005; revised January 19, 2006. Matthias Kliegel1 and Theodor Jäger2 , 1 Department of Psychology, University of Zurich, Switzerland. 2 Department of Psychology, Saarland University, Saarbrücken, Germany. Email: [email protected](M. Kliegel) Correspondence and offprint requests to Dr. Matthias Kliegel, Department of Psychology, University of Zurich, Freiensteinstrasse 5, CH-8032 Zurich, Switzerland. Fax: 0041-1-6345189. Publisher Item Identifier S 1542-5908(06)10101-3/$20.00 c Copyright °2006 Yang’s Scientific Research Institute, LLC. All rights reserved. The online version posted on January 25, 2006 at http://www.yangsky.us/ijcc/ijcc41.htm

Ellis, 1996; Kliegel, Martin, McDaniel, & Einstein, 2002): First, an intended action has to be planned and encoded. Thereafter, the individual must accurately maintain the intention in memory throughout the retention phase (whose duration may vary, e.g., from seconds to months). Finally, when the appropriate opportunity is encountered, the individual has to become aware that an intended action waits to be carried out, and the specific intention may be retrieved and executed. The necessity to accurately carry out such prospective memory tasks occurs very frequently in everyday life, such as in situations where we are supposed to keep appointments, remember to buy birthday gifts, remember to hand an important document to a colleague on the next day, or to switch off the stove after cooking (see Crovitz, 1984; Terry, 1988). In conclusion, it is argued that the ability to prospectively remember is of enormous relevance for everyday life and for clinical populations, and thus also of considerable theoretical interest (see Ellis & Kvavilashvili, 2000; Kliegel & Martin, 2003). Most of the studies targeting prospective memory have applied laboratory-based prospective memory tasks. Typically, in such laboratory studies participants are primarily engaged in a continuous cognitive task (termed the ongoing task) such as a short-term memory task or a word rating task (e.g., Einstein & McDaniel, 1990; Kliegel, Martin, McDaniel, & Einstein, 2001). Additionally, participants are required to simultaneously carry out a prospective memory task, such as the selfinitiated remembering to press a button on the keyboard every 10 minutes or whenever a specified word appears during the ongoing task (e.g., Einstein, McDaniel, Richardson, Guynn, & Cunfer, 1995). Thus, to perform the prospective memory task, attention (sporadically) needs to be switched from the ongoing task to the intended action and its execution (McDaniel & Einstein, 2000). Besides these laboratory studies, some authors have applied naturalistic prospective memory tasks, that is, tasks that require the execution of intended actions in everyday life, such as remembering to keep appointments (Martin, 1986), to mail cards to the experimenter (Patton & Meit, 1993), or to log the time on an electronic device (Rendell & Thomson, 1993, 1999). This apparent variety of laboratory-based and naturalistic prospective memory tasks has been classified into event-based tasks, which demand the self-initiated execution of the intended action after the appearance of a specific, externally presented cue; and into time-based tasks, which require executing the intended action at a particular point in time or after a specific amount of time has elapsed (e.g., Einstein & McDaniel, 1996).

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By applying such paradigms involving time-based or eventbased prospective memory tasks, across the past few years there emerged an increasing body of literature investigating the nature of prospective memory processes (e.g., Martin, Kliegel, & McDaniel, 2003; McDaniel & Einstein, 2000; Smith & Bayen, 2004), the developmental trajectories of the ability to prospectively remember across the life-span (e.g., Henry, MacLeod, Phillips, & Crawford, 2004; Kliegel & Jäger, in press; Kvavilashvili, Messer, & Ebdon, 2001), and the clinical aspects of remembering to carry out intended actions (e.g., Kliegel, Phillips, Lemke, & Kopp, 2005; Maylor, Smith, Della Sala, & Logie, 2002). However, only very little is known about how the ability to prospectively remember is related to emotional influences, which is the scope of the remainder of this article. II. T HE I NTERACTION OF C OGNITION AND E MOTION Psychological research aiming to explore how cognition operates devotes its main efforts in describing how information processing acts and which cognitive factors may influence this processing. Apart from the domain investigating emotionally neutral cognitive processing, an important (but still somewhat neglected) focus has been directed towards the relationship between cognition and emotion. Emotions and emotional states represent fundamental motivators for human-beings and are believed to be closely linked with cognition. For instance, our affects and feelings may provide important information that help evaluate persons or events. Moods and emotional states seem to exhibit relatively strong influences on both cognition and behavior. Obviously, a depressed person thinks and acts in a rather different manner than someone who is highly cheerful. In consequence, it seems particularly relevant for psychological research to investigate interactions between the brain circuits processing cognitive and emotional aspects of our experience, instead of considering emotion or cognition within separated domains of scholarly psychology. Indeed, at present the research on emotion and mood has become an established part of the purview of mainstream cognitive psychology (Clore & Martin, 2001). With respect to the interactions between emotions and the memory system, early studies were mainly interested in emotional influences on retrospective memory (e.g., Bower, Montiero, & Gilligan, 1978; Isen, Shalker, Clark, & Karp, 1978). Despite the increasing complexity of the findings and theories within this domain, there emerged some consistent phenomenon such as mood-congruent recall (i.e., the enhanced encoding and/or retrieval of material the affective valence of which is congruent with ongoing mood – see e.g., Blaney, 1986). Within this area of research, there is abundant (but not fully coherent) evidence that retrospective memory is susceptible to emotional influences (see e.g. Blaney, 1986; Martin & Clore, 2001, for reviews). For instance, retrospective memory performance seems to decline under the influence of negative emotions such as anxious or depressive emotional states (see e.g., Ellis & Ashbrook, 1988; Hertel & Milan, 1994). In contrast, the present article is targeted at providing a review over the much less ample evidence of emotional

influences on prospective memory. Importantly, this domain of research may be highly relevant in order to draw conclusions about the influence of day-to-day emotions, of fluctuations in mood, or of clinically relevant affective disorders on the persuasive ability to carry out intended actions in everyday life. The present paper first provides a brief overview over two psychological theories that have previously been used to derive hypotheses about the potential influences of emotions on prospective memory. Thereafter, we review the available findings of empirical studies investigating the relationship between emotions and prospective remembering. So far, we can only provide an overview about the effects of negative emotions on prospective remembering, since there exist no studies investigating the influence of positive emotions on the ability to execute future intentions. We then provide some new data of one of our recent studies, which explored how measures of naturally-occurring levels of anxiety and depression are related to performance in different types of prospective memory tasks. Finally, we discuss the current state of research on emotional influences on prospective memory and suggest some directions for future research. III. T HEORIES OF C OGNITION AND E MOTION The research considering the connectivity between emotions and cognition has inspired many theorists to establish models and theories describing the mechanisms how emotions might influence cognition and behavior (see Martin & Clore, 2001, for a review). Two of these theories will be described, since they have previously been used to derive hypotheses about the potential influences of emotions on prospective memory performance: (A) the Resource Allocation Model by Ellis and Ashbrook (1988) and (B) the Processing Efficiency Theory put forward by Eysenck and Calvo (1992). Whereas Ellis and Ashbrook’s model is concerned with the potential influences of depression or depressive emotional states on cognitive task performance, the Eysenck and Calvo theory is targeted at revealing the same relationship for anxiety or anxious emotional states. A. Ellis and Ashbrook’s (1988) Resource Allocation Model Ellis and Ashbrook’s (1988) Resource Allocation Model was designed to account for the effects of depressed mood states on memory in general. The model posits that depressive mood affects the amount of attentional capacity that can be allocated to a cognitive task at hand. The core assumption of Ellis and Ashbrook is that depression or depressive states result in a reduction of overall cognitive capacity by deflecting some amount of attentional resources to intrusive, taskirrelevant or depression-related thoughts during performance in a task (see also Ellis, 1991; cf. Hartlage, Alloy, Vazquez, & Dykman, 1993). As a result, performance declines in such cognitive activities, with a more pronounced deleterious effect of depression on cognitive tasks that require a high degree of self-initiated, controlled processes. This prediction is largely supported by studies investigating retrospective memory in

¨ KLIEGEL & JAGER, EMOTIONAL INFLUENCES ON PROSPECTIVE MEMORY

depression using tasks that require different levels of cognitive effort (e.g., Ellis & Ashbrook, 1988; Hertel & Hardin, 1990; Hertel & Milan, 1994; see Hartlage et al., 1993, for a review). B. Eysenck and Calvo’s (1992) Processing Efficiency Theory Eysenck and Calvo’s (1992) Processing Efficiency Theory is basically designed to provide an explanation of the effects of anxiety or anxious states on performance in cognitive tasks by describing a complex interplay between these variables. According to the theory, anxiety has motivational as well as attentional effects. The motivational effect is generally positive in that it leads to increased effort in a cognitive task situation. The attentional effect of anxiety consists of a disruption of the storage and processing capacity of the working memory system by this diminishing the amount of attentional resources that are available for a cognitive task. Thus, the theory posits that anxiety may either enhance or adversely affect cognitive task performance depending on several factors. Specifically, with regard to the motivational effect, Eysenck and Calvo predict that highly anxious individuals perform equally well or even better than less anxious individuals in relatively easy tasks or in tasks perceived as primary, because fear of adverse outcomes will lead an anxious individual to preferentially allocate resources to ensure success on that task. By contrast, anxiety is predicted to interfere with highly capacity demanding tasks or with tasks treated as less important because distracting thoughts associated with state anxiety (e.g., worry) compete for limited resources, which represents the attentional effect of anxiety. Several lines of evidence revealed that the Processing Efficiency Theory seems to explain the effects of anxiety on cognitive performance better than other theoretical approaches (see Eysenck & Calvo, 1992). In conclusion, the work of Ellis and Ashbrook (1988) and Eysenck and Calvo (1992) consist of comprehensive models of potential influences of distinct emotions on cognitive task performance. Whereas both theories have received relatively consistent support by studies investigating retrospective memory, there is little information whether the theoretical assumptions also apply to prospective memory. Nevertheless, these theories were useful for deriving hypotheses regarding the influence of negative emotions such as anxiety or depression on prospective memory performance in previous studies. In the next section, we review in more detail the studies investigating the relationship between negative emotional states and prospective memory. IV. E MOTIONAL I NFLUENCES ON P ROSPECTIVE M EMORY In this section, we initially review studies examining the relationship between unspecific forms of negative emotions and prospective memory performance. Thereafter, studies are described that were designed to test the relationship between prospective remembering and the more specifically circumscribed emotions of (1) anxiety and (2) depression. To the best of our knowledge, Meacham and Kushner (1980) provided the earliest investigation that was concerned about the influence of unspecific emotion variables on prospective

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remembering. These authors contrasted two competing hypotheses regarding the influence of emotional appraisal of an intended action on the probability of its execution. The first hypothesis predicted that high discomfort with a planned action leads to a high probability of completely forgetting to carry out the intention. A persuasive example of such a prospective memory situation that is accompanied by feelings of high discomfort or even anxiety could be to keep an appointment at the dentist’s for a painful treatment. This hypothesis was derived from the Freudian assumption that a memory content that is painful might be repressed, and the intended action thus forgotten. The second, competing hypothesis predicts that strong discomfort with a specific intended action leads to a high probability that the intended action is remembered, but that it is not carried out because of the resistance to carry out the aversive intention. To contrast these competing hypotheses, Meacham and Kushner administered a questionnaire to 73 younger and middle-aged adults to ask them how they perceived the relationship between prospective memory performance and the extent to which they feel comfortable with a given intended action. The self-report data revealed that planned actions that are highly aversive are more likely remembered but not carried out, rather than completely forgotten. In other words, the findings conformed much better with the second hypothesis than with the first, “Freudian” hypothesis. To summarize, Meacham and Kushner’s study provided first evidence that the emotional valence of an intended action seems to exhibit effects on the likelihood that the task is remembered and carried out. For discomfortable intentions, it seems that they are remembered very accurately, perhaps as a result of greater activation and/or rehearsal processes in memory. However, such aversive intentions may have a relatively high probability of remaining unperformed. A second investigation of the influence of unspecific negative emotions on prospective remembering is the questionnaire study by Schmidt (2004). Here, a large sample of college students was asked about their personal memories from the 9/11 attacks on the World Trade Center and the Pentagon. Most central for the purposes of the present paper, two questions of Schmidt’s questionnaire required the participants to rate whether the attacks had a deleterious effect on the execution of real-life prospective memory tasks during the day of the attacks (e.g., attending appointments or carrying out errands). The self-reports indicated that individuals who were strongly emotionally aroused by the attacks exhibited more prospective memory failures on that day relative to those who reacted less emotionally aroused when hearing the news of the plane crashes. In conclusion, Schmidt’s findings provided evidence that states of highly negative emotions may impair prospective remembering in everyday life. With regard to the influence of more specific negative emotions, we now describe studies examining the impact of anxiety or anxious emotional states on prospective memory, followed by a discussion of findings about influences of depression or depressive emotional states on prospective remembering. Cockburn and Smith (1994) published the first study which investigated the impact of inner-states of experienced anxiety on prospective memory performance in a sample of 119 older

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adults1 . Participants were required to indicate their current levels of anxiety during the experiment on a visual analogue scale2 . The prospective memory task was taken from an established battery for testing (mainly retrospective) memory functioning (i.e., from the Rivermead Behavioural Memory Test [RBMT]; Wilson, Cockburn, & Baddeley, 1985). This task requires the participants to ask the experimenter about an appointment on hearing a timer that has been set to ring during the test session (i.e., an event-based prospective memory task). To examine the influence of levels of anxiety, the participants were divided into 7 discrete categories of anxiety levels. The results of Cockburn and Smith revealed that the highest probability to successfully carry out the intended action was associated with either low or high levels of anxiety, whereas intermediate levels of anxiety were associated with relatively low success rates in the prospective memory task. The high performance of the anxious participants was explained with their putative tendency to frequently check and/or rehearse their intentions or to engage in more elaborate encoding of the intention than participants experiencing intermediate levels of anxiety. However, no explicit explanation was given for why the participants reporting very low levels of anxiety also performed equally well in the prospective memory task. Nevertheless, the findings by Cockburn and Smith indicated that high levels of anxiety might favour success in some prospective memory tasks (rather than being deleterious for good performance, as could be expected from an intuitive standpoint). Nigro and Cicogna (1999) applied both a time-based and an event-based prospective memory task to a sample of 40 undergraduate students. During the experiment, the State-Trait Anxiety Inventory (STAI; Spielberger, Gorsuch, & Lushene, 1983) was administered to the participants to obtain measures of state anxiety and trait anxiety. Whereas trait anxiety refers to the stable disposition towards high levels of psychophysiological arousal, state anxiety is defined as the actual anxiety at a particular moment, which is determined by both trait anxiety and situational threat. The ongoing task of Nigro and Cicogna consisted of a question-answering task that was performed on the computer screen. In the time-based prospective memory task, participants had to press a designated key every 10 minutes. In the event-based prospective memory task, along with each new question of the ongoing task an additional picture was shown at the bottom of the screen for a short time. Participants were instructed to press a target key every time the picture showed an animal. Unfortunately, since the relationship between anxiety and prospective memory performance was not in the primary scope of Nigro and Cicogna’s study, they did not provide a full description of the data that would be of interest for the present review. It was reported that, irrespective of the type of prospective memory task, higher 1 Note that Cockburn and Smith (1994) also assessed self-rated depression among their participants. However, no relationship emerged between depression and prospective memory performance and, in consequence, this potential relationship was not discussed further. 2 A visual analogue scale as the one used by Cockburn and Smith (1994) requires placing a mark on a horizontal line, the leftmost end of which indicates “not at all anxious” and the rightmost end “very anxious”.

levels of state anxiety were associated with shorter latencies of the prospective memory responses. In other words, highly anxious participants responded faster after the appearance of to the event-based prospective memory cues and were closer to the time-based prospective memory target times (note that no results were provided regarding the question whether anxious participants also executed the intended action more frequently). In concluding, Nigro and Cicogna interpreted the better performance of the highly anxious participants as evidence that anxiety leads people to monitor the environment and the passage of time more frequently, which might lead to better prospective memory performance. Harris and Menzies (1999) investigated the influence of the mood states of anxiety and depression on both prospective and retrospective memory performance. With regard to the potential effects of anxiety, Harris and Menzies explicitly referred to Eysenck and Calvo’s (1992) Processing Efficiency Theory. Specifically, the assumption of the theory that the deleterious effects of anxiety more probably emerges in tasks treated as “secondary” rather than “primary” was used to predict that prospective memory performance should be particularly susceptible to the adverse effects of inner-states of anxiety. In their study, Harris and Menzies sought to reveal the unique contributions of anxiety and depression on prospective memory performance. The participants consisted of a nonclinical sample of 101 undergraduate students. The short form of the Depression Anxiety Stress Scales (DASS; Lovibond & Lovibond, 1995) was applied to obtain measures of anxiety, depression, and stress. During the ongoing task in which the prospective memory task was embedded, participants were required to generate semantic associates to each of 60 spoken words and to remember the spoken words for a later retrospective memory test. The prospective memory task consisted of placing an “x” beside items belonging to the categories clothing or body parts (i.e., an event-based prospective memory task). To control for potential contributions of retrospective memory failures for low prospective memory performance, Harris and Menzies excluded participants that had not understood or remembered the prospective memory instruction when queried after the experiment. The results of a multiple regression analysis simultaneously considering the effects of anxiety and depression showed that higher prospective memory performance was significantly predicted by lower levels of self-reported anxiety. By contrast, the trend of an association between lower levels of self-reported depression with better prospective memory performance failed to reach statistical significance. Finally, self-reported stress was only a weak and non-significant predictor for prospective memory performance. The results for the retrospective memory measure were somewhat different, since no emotion measure accounted for a unique proportion of variance in retrospective memory performance. To sum up, in Harris and Menzies’ (1999) study, participants reporting elevated anxiety and depression showed a higher probability to score lower in the prospective memory task, but anxiety seemed to play a slightly stronger role than depression. By contrast, no unique influence of the emotion variables was found for retrospective memory performance. Hence, Harris and Menzies provided


evidence that negative emotional states might interfere with the accurate remembering to carry out future intentions, but not with the accurate remembering of past information. In a follow-up study, Harris and Cumming (2003) focused on the influences of state anxiety and trait anxiety on performance in different forms of memory tasks (i.e., prospective, retrospective, and working memory tasks). State and trait anxiety were again assessed with the STAI (Spielberger et al., 1983). The participants were 63 healthy undergraduate students, who were divided into three groups according to the level of self-reported state and trait anxiety. With respect to the cognitive tasks being used, Harris and Cumming aimed to improve the methodology of their previous Harris and Menzies (1999) study. In the previous study, the prospective and retrospective memory tasks had differed in a number of ways apart from the differences that arise from the inherent characteristics of these two types of memory tasks. Specifically, the characteristics that Harris and Cumming now tried to match were the amount of information that needed to be remembered, the specificity of the cues that were available for remembering, the amount of time between the encoding and the retrieval of the material, and the amount of competing activity that occurred at the time of retrieval. The efforts of Harris and Cumming to match the prospective and retrospective memory tasks were aimed to determine whether state anxiety truly influences only prospective memory but not retrospective memory, as was found in the Harris and Menzies (1999) study. The paradigm of Harris and Cumming (2003) consisted of encoding a study list of 10 words, which later appeared during a semantic association task that was started 10 minutes after the encoding of the study list. The semantic association task was virtually the same as in the Harris and Menzies (1999) study. Additionally, participants were instructed that during this ongoing task the study words would appear again and that when confronted with one of these words they should not perform the ongoing task but instead write down the encoded word itself. Importantly, before starting the first half of the ongoing task, participants were not reminded of this additional task; thus the responses to the study words within the first half of the ongoing task were taken as indicators for (event-based) prospective memory. Then, during a short break between the first and the second half of the ongoing task, participants were explicitly reminded of the instruction to write down the word of the study list instead of performing the ongoing task. Therefore, the responses to the study words during the second half of the ongoing task were

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taken as indicators of retrospective memory3 . Additionally, Harris and Cumming administered a test to assess the participants’ working memory capacity (i.e., reading span task). The analyses of Harris and Cumming revealed that participants reporting high state anxiety performed significantly worse in the prospective memory task than their low- and mediumanxious counterparts. By contrast, the extent to which state anxiety was reported was not correlated with the measures of retrospective and working memory4 . Additionally, trait anxiety had no comparable effects as state anxiety, indicating that the latter exerts a more direct influence on cognitive task performance than the former (cf. Eysenck & Calvo, 1992). Harris and Cumming concluded that – consistent with their expectations derived from the Processing Efficiency Theory – prospective memory was susceptible to the deleterious effects of high levels of anxiety, whereas retrospective memory was not, by this replicating the findings of Harris and Menzies. We now turn to the discussion of studies that investigated the impact of depression or depressive emotional states on prospective memory performance. Two of the previously reported studies already examined the effects of depression – besides those of anxiety – on prospective remembering, but both studies did not discuss this relationship more thoroughly since in one study there was no (Cockburn & Smith, 1994 – see Footnote 1) and in the other only a marginally significant (Harris & Menzies, 1999) relationship between self-reported depression and prospective memory performance. Therefore, we now present studies that were specifically designed to test the influence of depression on the ability to carry out future intentions. In a clinical study, Rude, Hertel, Jarrold, Covich, and Hedlund (1999) investigated whether patients suffering from major depression have deficits in the ability to perform intended actions. These authors administered a time-based prospective memory task as well as psychometric tests of verbal ability and retrospective memory (i.e., the Wechsler Memory Scale Revised [WMS-R]; Wechsler, 1987) to a community sample of 20 clinically depressed younger adults. For comparison, 3 One potential limitation of Harris and Cumming’s (2003) study is that the prospective and the retrospective memory tasks were so closely matched that it might be questioned whether they truly reflected the characteristics of prospective versus retrospective memory tasks. Given that the responses to the study words were also delayed in the second half of the ongoing task, these might also be considered as prospective responses (which are, however, much less reliant on self-initiated retrieval processes than those of the first half of the ongoing task) rather than retrospective responses, since introducing a delay between the prospective memory instructions and the start of the ongoing task is no obligatory prerequisite in prospective memory research. Assuming that the responses in the second half of the ongoing task exclusively reflect retrospective memory implies that the reminder about how responding to the study words was rehearsed in working memory all the time throughout the second half of the ongoing task, which might not have been the case. Therefore, the effort of Harris and Cumming to equate the prospective and the retrospective memory tasks as closely as possible has to be commended, but it remains unclear whether the matched tasks still properly reflect the distinction between prospective and retrospective memory tasks. 4 Harris and Cumming (2003) attributed the (unexpected) null-effect of state anxiety on working memory capacity to the relatively low difficulty of the working memory task. However, note that this argument might also be partly true for the retrospective memory task, since performance was substantially higher in the retrospective memory task relative to the prospective memory task, indicating that a ceiling effect in the retrospective memory measures might have masked performance differences due to state anxiety.

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they administered the same tasks to a sample of non-depressed adults matched in age, educational attainment, ethnicity, and gender. Participants were engaged in an ongoing task on the computer screen, which consisted of multiple-choice general knowledge questions. The time-based prospective memory task was to press a specified key on the keyboard every 5 minutes while performing the ongoing task. To monitor the time, participants could press another key and a digital time counter would appear on the screen. Based on previous findings of cognitive impairment of depressive patients and of particular deficits in tasks that heavily rely on self-initiated, controlled processes (Hartlage et al., 1993), Rude et al. predicted an impairment of the clinically depressed participants in the prospective memory task relative to their healthy counterparts, particularly because time-based tasks are generally assumed to involve a high degree of self-initiated, controlled processing (e.g., d’Ydewalle, Bouckaert, & Brunfaut, 2001). Rude and colleagues found that the two groups did not differ in performance in the tests of retrospective memory, but that the depressed patients scored significantly lower in the prospective memory task. In other words, the depressed patients were not as able as their non-depressed counterparts to remember to press the target key as timely as possible5 . The lower prospective memory performance of the depressed patients partly resulted from a reduced monitoring of the passage of time, since the non-depressed participants monitored the clock significantly more often than the patients, particularly in the time period immediately prior each prospective memory target time. Interviewing the participants about the prospective memory instructions revealed that the depressed patients did not solely respond less well in the prospective memory task because they did not retrospectively remember the instructions (which might have been expected in the light of retrospective memory deficits of depressed patients – see e.g., Burt, Zembar, & Niederehe, 1995). In conclusion, the results of Rude and colleagues conformed with their hypothesis that depression results in impairments in prospective memory tasks that require a high degree of controlled, self-initiated processing, a pattern that had already been found within the realm of retrospective memory (e.g., Hertel & Hardin, 1990; Hertel & Milan, 1994). Livner, Berger, Jones, and Bäckman (2005) presented data of a study that further investigated the relationship between depressive emotional states and prospective memory performance. In a large-scale study, the extent to which depressive symptoms were experienced was assessed with the Comprehensive Psychopathological Rating Scale (CPRS; Asberg & Shalling, 1979) in a sample of 410 older adults. The prospective memory task was to remind the experimenter to make a phone call after the completion of a large cognitive test battery (i.e., an event-based prospective memory task). Livner and colleagues also investigated the influence of depression on a measure of retrospective memory (i.e., free recall of a 5 One limitation of Rude et al.’s (1999) findings is that the depressed patients also scored lower in the ongoing task relative to the control group, and the patients exhibited somewhat lower scores in verbal ability (as assessed by a vocabulary test). Therefore, the possibility remains that the depressed adults scored lower than the control group in the prospective memory task because the two groups were not matched in level of cognitive functioning or general intelligence.

wordlist). Surprisingly, the results revealed that prospective memory performance was unaffected by the severity of depressive symptoms. By contrast, retrospective memory task performance was better in participants being relatively free from depressive symptoms. Based on this outcome, Livner et al. concluded that retrospective memory – but not prospective memory – seems to be disrupted by depression. Recently, our research group conducted a study investigating the role of depressive mood states on the ability to carry out future intentions (Kliegel, Jäger, et al., 2005). To the best of our knowledge, this was the first study that used an experimental manipulation of the inner emotional state of participants in order to investigate this relationship. This was achieved by applying a mood induction procedure (see Albersnagel, 1988; Gerrards-Hesse, Spies, & Hesse, 1994; Martin, 1990, for reviews), which are techniques aimed to induce specific emotional states in participants by exposing them to emotional material such as affectively valenced film segments, stories, or music, etc. (e.g., Kliegel, Horn, & Zimmer, 2003; Kliegel, Jäger, & Phillips, under revision). In our study, half of the participants, who were 62 healthy undergraduate students, were presented with a film segment that was highly likely to evoke sadness and depressive feelings, whereas the other half of the participants watched an emotionally neutral film segment (participants were randomly assigned to these two conditions). After being exposed to this mood induction, participants performed an ongoing task that was assumed to impose relatively high demands on the working memory system (i.e., the n-back task). Additionally, participants were instructed to perform a time-based prospective memory task, which consisted of remembering to press a target key every minute as timely as possible after the start of the ongoing task. To monitor the time, a digital time counter on the computer screen could be activated for a short time by pressing the “space”-key on the keyboard. The effects of the mood induction were assessed by a mood questionnaire that assesses the three mood dimensions of pleasantness, calmness, and wakefulness (MDBF; Steyer, Schwenkmezger, Notz, & Eid, 1994, 1997). The mood questionnaire was administered three times to accurately trace the participants’ mood changes across the entire experimental procedure: before the mood induction, immediately after the mood induction, and at the end of the experiment when the ongoing task and the prospective memory task were finished. Based on Ellis and Ashbrook’s (1988) Resource Allocation Model, which predicts that depressed mood is associated with a decrement in the allocation of cognitive resources to a current task (especially when the task requires a high degree of self-initiated activities such as a time-based prospective memory task), we hypothesized that participants who experienced highly negative emotions as a response to the mood induction would perform worse in the prospective memory task than those who were not confronted with the highly emotional film segment. The data revealed that the depressing movie successfully induced a relatively large decrement in experienced pleasantness and calmness in a subgroup of participants (i.e., the Mood Responders). By contrast, some participants (i.e., the Mood Non-Responders) did not substantially change their mood as a


response to the negative mood induction, presumably because they engaged in relatively neutral cognitive processing of the film segment since we applied the mood induction without explicitly instructing the participants to induce themselves into a state of sadness. As expected, mood of the participants assigned to the neutral mood induction (i.e., the Neutral Mood Group) did not fluctuate substantially throughout the entire experimental procedure. Thus, the mood induction was regarded as having successfully induced a substantial proportion of participants into a highly negative emotional state. However, towards the end of the experiment the Mood Responders apparently regained a better mood, that is, they shifted towards the other two groups with respect to their inner-states of emotions. Based on similar findings of other studies (see Kliegel et al., under revision) and based on the outcome of the mood induction, we investigated performance in the cognitive tasks for the first and the second half of the ongoing task, separately, since the effects of sad mood on cognitive performance were expected to be largest in the time period immediately after the negative mood induction. The examination of mood effects on cognitive task performance revealed that the mood manipulation seemed to have no effects on performance in the ongoing n-back task, which was surprising in light of previous findings that negative emotions may impair working memory performance (see Kensinger & Corkin, 2003). However, the relatively high performance in the ongoing task indicated that this task had a relatively low difficulty, which might have prevented potential influences of depressed mood on ongoing cognitive task performance (cf. Harris & Cumming, 2003). Turning to performance in the prospective memory task, we found the expected negative impact of induced depressive mood in the first half of the cognitive task: The Mood Responders performed significantly worse relative to the Neutral Mood group in the five minutes immediately following the depressing movie, which seemed to result from a substantially decreased timeliness of the prospective memory responses. By contrast, the prospective memory scores of participants who did not respond to the sad mood induction did not differ significantly from the Neutral Mood Group. Moreover, the impact of the negative mood induction on prospective memory performance interacted with time, as in the second half of the cognitive task the pattern of results changed strikingly: The Mood Responders now performed significantly better than in the first half of the task, and their performance was even slightly (but non-significantly) better than performance of the other two groups whose mood did not change over time. Figure 1 illustrates this dynamic temporal pattern of prospective memory performance of the three mood groups. Next, we examined the allocation of attentional resources to the prospective memory task, since Ellis and Ashbrook’s (1988) model explicitly predicts that induced depressive states diminish attentional resources that are devoted to a cognitive task. Fortunately, time-based prospective memory tasks allow the explicit assessment of attention allocation, since the participants’ clock checking can be recorded. Indeed, previous studies have found that clock checking frequency is an important mediator for time-based prospective memory

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Fig. 1. Prospective Memory Performance Across Time in the Kliegel, Jäger, et al. (2005) study. Note. Error bars represent the standard errors of the means.

performance, especially in the time period immediately before the prospective memory target times (e.g., Einstein et al., 1995; Kliegel et al., 2001); and this was also the case in our study (see also Rude et al., 1999). Moreover, in addition to the total number of clock checks we also investigated how timely these clock checks were. Specifically, we calculated the differences between the time points of each clock check and the target time when the next prospective memory response was to be made. Importantly, this examination of clock checking accuracy revealed a pattern that closely followed the pattern of prospective memory hits across time. In conclusion, clock checking behavior seemed to mediate prospective memory performance of the three mood groups: The participants that experienced a transient state of depressed mood monitored the clock less frequently and less accurately. Given that clock monitoring is assumed to reflect the amount of attentional resources devoted to a prospective memory task, we concluded that the sad mood induction had the expected effect of diminishing attentional resources as per Ellis and Ashbrook. In consequence, our study provided further evidence that transient states of depressive mood or clinically relevant depressive disorders seem to disrupt cognitively demanding tasks, such as the ability to carry out future intentions. To the best of our knowledge, these are the currently available findings on the relationship between (negative) emotional states and the ability to carry out intended actions. To summarize, the studies described so far indicated that unspecific negative emotions (Meacham & Kushner, 1980; Schmidt, 2004) and inner-states of anxiety (Harris & Cumming, 2003; Harris & Menzies, 1999) or depression (Kliegel, Jäger, et al., 2005; Rude et al., 1999; see also Harris & Menzies, 1999) seem to interfere with successful prospective remembering, although the findings are not without inconsistencies (Cockburn & Smith, 1994; Livner et al., 2005; Nigro & Cicogna, 1999). In the next section, we provide some new data of a recently conducted study, in which we further examined the influence of anxiety and depression on different kinds of prospective memory tasks.

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V. S OME N EW DATA Recently, we carried out a further laboratory study in which we investigated the relationship between naturally-occurring levels of specific negative emotions and prospective memory performance. To provide an integrated approach, we assessed both anxiety and depression rather than only one of these emotions (cf. Harris & Menzies, 1999), because it was argued that depression and anxiety frequently occur together and hence it would be of considerable theoretical interest to discover differences between the processes underlying anxiety- and depression-mediated effects on cognitive performance (e.g., Eysenck & Calvo, 1992; Harris & Menzies, 1999; Hartlage et al., 1993). Moreover, as previous studies have not considered whether different kinds of prospective memory tasks are differentially susceptible to the influence of negative emotions, we administered three different types of prospective memory tasks: an event-based and a time-based prospective memory task performed in the laboratory, and a naturalistic prospective memory task carried out in everyday life; We examined the degree to which performance in these different tasks was related to measures of anxiety and depression in a non-clinical sample of adults. With regard to both emotions, it was expected that high levels of negative emotion would be associated with lower performance in the prospective memory tasks, because Ellis and Ashbrook’s (1988) Resource Allocation Model predicts worse cognitive task performance in individuals experiencing depressive states, and because the Processing Efficiency Theory by Eysenck and Calvo (1992) predicts worse cognitive task performance in highly anxious individuals in demanding task situations or in tasks treated as “secondary”. However, we were specifically interested in the unique contribution of each of these emotion variables to disentangle the influences of depression- and anxiety-mediated effects on the ability to carry out intended actions. A. Method 1) Participants: A sample of 87 younger, middle-aged, and older adults between 18 and 91 years participated in this study (age: M = 44.11, SD = 18.94; 47 females). Most of the younger and the middle-aged adults were students of the University of Zurich, whereas the older adults were community-dwelling volunteers. The participants were all paid the equivalent of 8 US$ for their participation. The participants’ verbal ability was estimated by a German vocabulary test that consisted of 37 multiple choice tasks (MWT-A; Lehrl, Merz, Burkhard, & Fischer, 1991) of whom a mean of 32.01 tasks (SD = 2.87) were correctly answered. The participants reported having completed a mean of 14.24 years (SD = 3.14) of formal education. 2) Materials: Hospital Anxiety and Depression Scale (HADS). Current levels of anxiety and depression were assessed with the Hospital Anxiety and Depression Scale (HADS; Zigmond & Snaith, 1983). The HADS has been found to show good psychometric properties and to perform well in assessing symptom severity of anxiety and depression disorders in health settings and in the general population (see

Bjelland, Dahl, Haug, & Neckelmann, 2002; Herrmann, 1997, for reviews). The scale consists of 14 items equally divided between anxiety and depression subscales. Each item can be answered on a four point (0-3) scale. Thus, for each subscale, scores range from 0 to 21; a score of between 0 and 7 is regarded as being in the normal range, a score of between 8 and 10 identifies possible or mild cases, and a score of 11 or more indicates the probable presence of a clinically meaningful anxiety or depression condition (Zigmond & Snaith, 1983). 3) Ongoing Task: We used the n-back task as the ongoing task in which both laboratory-based prospective memory tasks were embedded (cf. Jäger & Kliegel, submitted). The n-back task is thought to place relatively heavy demands on working memory and information processing resources. On a computer screen, participants viewed pseudo-random sequences of the Snodgrass and Vanderwart (1980) pictures, which depicted well-known objects (such as a banana, a ball, an ashtray, a hand, a cup, etc.). Each picture was displayed for 4 s and was followed by a 1 s inter-stimulus interval. Participants were instructed to press a “yes”-key if the picture was the same as that which occurred two before, otherwise a “no”-key had to be pressed (i.e., a 2-back task). The n-back task consisted of 122 trials (maximum hits = 40) and lasted 10 minutes and 10 s. The number of correct responses was obtained by adding correct rejections and hits for each participant. • Event-based prospective memory task. This task was to remember to press a target key whenever a picture depicting an animal appeared during the n-back task. In total, five targets appeared during the ongoing task, which occurred at 1:50, 3:50, 5:50, 7:50, and 9:50 minutes in order to closely parallel the occurrence of the event-based prospective memory targets to the time-based prospective memory target times (see below). Every hit on the target key that occurred within 5 s after the presentation of a target was scored as event-based prospective memory hit. • Time-based prospective memory task. This task was to remember to press a target key at two minute intervals from the start of the n-back task as accurately as possible. To monitor the time, participants could press the “space”key to see a time counter clock [“00:00”] which appeared for 3 s. To analyze time-based prospective memory performance, we set a target window of 5 s (± 2.5 s) around the target times (cf. Kliegel et al., 2001). Every hit on the target key that occurred within this target window was scored as time-based prospective memory hit. To investigate clock monitoring behavior, we focused on the 30-second time interval immediately prior each target time, as this is likely to be the critical time period in making an accurate time-based prospective memory response (see e.g., Einstein et al., 1995), but we also examined each 2-minute-period preceding the target times by dividing it into four 30-seconds-intervals in order to investigate if participants showed strategic clock monitoring (Kliegel et al., 2001). Within the 30-seconds-interval prior to the target times, the number of clock-checks (i.e., clock checking frequency) and the mean time deviations of the clock checks from the exact prospective memory target times (i.e., clock checking accuracy) were investigated


•

(cf. Jäger & Kliegel, submitted; Kliegel, Jäger, et al., 2005). Naturalistic prospective memory task. This task was administered only to a subset of 30 participants (age: M = 43.27, SD = 9.11; 17 females). For this naturalistic prospective memory task, participants were given a questionnaire assessing self-esteems of memory ability. They were instructed to fill the questionnaire out at home and to send it back exactly one week after the laboratory session. Based on the postal stamps, a score of 2 was assigned if a participant posted the questionnaire exactly 7 days after the laboratory session, a score of 1 was assigned if a participant posted the questionnaire on an incorrect day, and a score of 0 was assigned if a participant failed to post the questionnaire completely.

4) Procedure: Participants were invited to the laboratory for participating in a study on memory abilities. Each participant was tested individually. Initially, participants gave informed consent, provided socio-demographic information, and filled in the HADS. Then, the instructions for the nback task were given, followed by practice trials of the nback task. Participants performed the n-back task twice more in concert with the event-based or the time-based prospective memory task (the order of the two tasks was counterbalanced across participants). Each prospective memory task began with instructions for the tasks. Participants were then required to repeat all their tasks in order to check for understanding. Thereafter, a distracter task was given. After this delay of approximately 5 minutes, the experimenter started the first nback/prospective memory task. After completion, retrospective memory for the embedded prospective memory task was obtained. Then, the experimenter continued with the procedure of the second prospective memory task that was identical to the first prospective memory task with the exception of the type of the task. At the end of the procedure, participants were debriefed, and the 30 adults who received the naturalistic prospective memory task were given the questionnaire with the instruction to fill it out at home 7 days later and to post it exactly on the 7th day after the laboratory session.

B. Results In all of the subsequently reported results inferring statistical significance, the alpha-level was set at α = 0.05 or lower. All 87 participants were able to correctly recall the prospective memory task instructions and thus no participant was excluded from the analyses. First, we report the scores of the HADS, followed by the participant’s performance in the cognitive tasks. Thereafter, we provide the analyses about the relationship between the anxiety and depression scores and cognitive task performance. 1) HADS scores.: In self-rated anxiety, the participants scored a mean of 5.02 (SD = 2.66; range= 1-13). In selfrated depression, the mean score was 2.57 (SD = 1.97; range= 0-8). There was a positive correlation between these two measures confirming that anxiety and depression frequently co-occur, r(87) = 0.54, p < 0.001.

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2) Ongoing task performance.: The mean number of correct n-back task responses was 112.79 (SD = 5.45) for the event-based and 111.90 (SD = 6.64) for the time-based prospective memory task. This difference was significant, F (1, 86) = 4.15, p < 0.050. 3) Laboratory prospective memory performance.: The mean number of prospective memory hits was significantly higher in the event-based (M = 4.70; SD = 0.72) than in the time-based task (M = 3.76; SD = 1.50), F (1, 86) = 30.96, p < 0.001. With regard to the time-based task, participants clearly applied a strategic clock monitoring behavior, since they steadily increased the number of clock checks across the four 30seconds-intervals prior each prospective memory target time (mean number of clock checks from the 1st to the 4th time interval: 3.31, 4.60, 6.52, & 12.21), F (2, 258) = 235.31, p < 0.001. As expected, clock checking frequency within the 30-seconds-interval directly preceding the prospective memory target times was significantly correlated with the number of time-based prospective memory hits, r(86) = 0.65, p < 0.001. Moreover, also clock checking accuracy within the same time interval was significantly correlated with the number of time-based prospective memory hits, r(86) = −0.34, p < 0.010. However, clock checking frequency and clock checking accuracy were not correlated, r(86) = 0.04, p = 0.694. In sum, this pattern shows that both clock checking frequency and clock checking accuracy are important and statistically independent predictors for success in time-based prospective memory (a multiple regression predicting timebased prospective memory hits confirmed that both clock monitoring measures significantly contributed to performance; β = 0.63 for clock checking frequency and β = −0.37 for clock checking accuracy; ps < 0.001) (cf. Jäger & Kliegel, submitted). 4) Naturalistic prospective memory task performance.: Of the 30 participants to whom the naturalistic prospective memory task was administered, 12 participants posted the questionnaire exactly 7 days after the laboratory session (i.e., they received a score of 2), 9 participants posted the questionnaire on an incorrect day (i.e., they received a score of 1), and 9 participants failed to post the questionnaire (i.e., they received a score of 0). 5) Influence of anxiety and depression on ongoing task performance.: Neither self-rated anxiety nor self-rated depression were significantly correlated with ongoing task performance, 0 > rs(87) > −0.18, ps > 0.103. 6) Influence of anxiety and depression on laboratory prospective memory performance.: With regard to the relationship between the HADS scores and the scores in the laboratory prospective memory tasks, a differential pattern emerged across the type of task: In the time-based task, a greater number of prospective memory hits was marginally significantly associated with lower scores in depression, r(87) = −0.18, p = .088. Thus, higher levels of experienced depression were associated with lower time-based prospective memory performance. By contrast, prospective memory performance was uncorrelated with anxiety, r(87) = 0.01, p = 0.904. Strengthening these results, the partial correlation between

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time-based prospective memory hits and depression when controlling for anxiety was significant, r(84) = −0.23, p < 0.050, whereas the partial correlation between time-based prospective memory hits and anxiety when controlling for depression was not, r(84) = 0.14, p = .212. However, the HADS scores indicating anxiety or depression were not significantly correlated with the measures of clock checking frequency (r(87) = −0.14, p = 0.188 for depression; r(87) = −0.09, p = 0.392 for anxiety) or clock checking accuracy (r(86) = 0.05, p = 0.679 for depression; r(86) = −0.08, p = 0.444 for anxiety) within the 30-seconds-interval preceding the prospective memory target times, although the strongest of these non-significant correlations (i.e., the correlation between depression and clock checking frequency indicating fewer clock checks of participants experiencing higher levels of depression) was consistent with the associated pattern of diminished prospective memory performance in participants reporting the highest levels of depression. Conversely, in the event-based task, a greater number of prospective memory hits was significantly associated with lower scores in anxiety, r(87) = −0.22, p < 0.050. In other words, higher levels of experienced anxiety seemed to be associated with lower event-based prospective memory performance. By contrast, prospective memory performance was uncorrelated with depression, r(87) = −0.12, p = 0.287. Again strengthening these results, the partial correlation between event-based prospective memory hits and anxiety when controlling for depression approached significance, r(84) = −0.18, p = 0.090, whereas the partial correlation between event-based prospective memory hits and depression when controlling for anxiety did not, r(84) < 0.01, p = 0.990. Two multiple regression analyses were performed to simultaneously consider the shared variance of the two predictors anxiety and depression with prospective memory performance. In the regression model predicting time-based prospective memory, the influence of depression was significant, β = −0.27, p < 0.050, whereas the influence of anxiety was not, β = 0.16, p = 0.212. In the regression model predicting event-based prospective memory, the influence of anxiety approached significance, β = −0.22, p = 0.090, whereas the influence of depression did not, β = 0.002, p = 0.990 (note that in both multiple regressions, the inclusion of two additional predictor variables, i.e., measures of verbal ability and years of formal education, did not change this pattern of results, indicating that these two variables do not seem to confound the obtained results). 7) Influence of anxiety and depression on naturalistic prospective memory performance.: Better scores in the naturalistic prospective memory task were significantly associated with higher scores in anxiety, r(30) = 0.42, p < 0.050, and marginally significantly with higher scores in depression, r(30) = 0.32, p = 0.086. When investigating the partial correlations between the scores in the naturalistic prospective memory task and one of the HADS scales when controlling for the other HADS scale, neither of these partial correlations were significant, rs(27) < 0.31, ps > 0.106, indicating that depression and anxiety had no unique but rather an overlapping predictive value for the scores in the naturalistic prospective

memory task. Similarly, in a multiple regression predicting the scores in the naturalistic prospective memory task neither of the HADS scales had a significant unique predictive value alone, βs < 0.36, ps > 0.106. C. Discussion The present study aimed at further elucidating the potential influences of negative emotional states on the ability to carry out intended actions. For this purpose, we invited participants to a laboratory session in which they were required to perform a time-based as well as an event-based prospective memory task, which were embedded within the n-back working memory task. Moreover, a naturalistic prospective memory task was performed by a subset of participants in their everyday life. To relate the scores in these cognitive tasks to emotion variables, we assessed the participants’ current levels of anxiety and depression with the Hospital Anxiety and Depression Scale (HADS; Zigmond & Snaith, 1983). Based on previous findings and predictions derived from the theories of Ellis and Ashbrook (1988) and Eysenck and Calvo (1992), we expected that higher levels of anxiety and depression would be associated with lower performance in the cognitive tasks, particularly in the prospective memory tasks. Furthermore, we aimed at disentangling the unique contribution of depression and anxiety on prospective memory performance, since these two emotion variables frequently co-occur (see Harris & Menzies, 1999). The correlational analyses and the multiple regressions revealed a multifaceted pattern of results. First, neither levels of anxiety nor levels of depression were significantly associated with performance in the ongoing task (i.e., the n-back task), indicating that anxiety and depression had no costs on performance in this task. However, in the light of the high performance in the n-back task (i.e., around 92% correct responses), the lack of potentially deleterious effects of the emotion variables might have been due to the relatively low difficulty of this task (cf. Kliegel, Jäger, et al., 2005). In other words, the participants’ attentional resources might not have been overcharged by the n-back task, by this enabling good performance even in individuals whose attentional resources were diminished through high levels of anxiety or depression. Indeed, Ellis and Ashbrook (1988) and Eysenck and Calvo (1992) predict that unless tasks are sufficiently taxing of resources, a deleterious effect of the negative emotion on performance will not be evident. However, the prospective memory tasks required attentional resources additional to those necessary for the n-back task. Therefore, it is of particular interest whether the execution of the intended actions might have been more sensitive for the impact of anxiety and depression on basic cognitive resources. With regard to the performance in the event-based and the time-based prospective memory tasks, a differential pattern of results emerged. Event-based prospective memory performance seemed to be disrupted by heightened levels of anxiety, but not by heightened levels of depression. Conversely, timebased prospective memory performance was subject to the adverse impact of depression, but not to the impact of anxiety.


Thus, the two types of tasks were differentially sensitive to the influences of negative emotions. Anxiety seemed to exert a unique influence on event-based prospective remembering, and depression appeared to uniquely influence timebased prospective remembering. Turning to performance in the naturalistic prospective memory task, the direction of the relationship between negative emotions and task performance changed strikingly: Here, better performance in the naturalistic prospective memory task was achieved by individuals experiencing relatively higher levels of anxiety and depression. The adverse impact of anxiety on event-based prospective memory performance might be interpreted within Eysenck and Calvo’s (1992) framework as further indication that the ability to carry out event-based intentions is susceptible to the deleterious effects of inner-states of anxiety. According to Eysenck and Calvo, the working memory’s storage and processing capacity is disrupted in highly anxious individuals, which diminishes the amount of attentional resources that are available for a cognitive task. The fact that only eventbased prospective memory performance, but not ongoing task performance, was influenced by anxiety is consistent with the more specific prediction by Eysenck and Calvo that anxiety typically has an adverse effect on tasks treated as secondary rather than on tasks treated as primary if one assumes that participants perceived the continuously running n-back task as relatively more primary than the sporadic execution of the intended action. In conclusion, our finding that individuals experiencing heightened levels of anxiety perform worse in some prospective memory tasks is consistent with Eysenck and Calvo’s Processing Efficiency Theory and with previous findings reporting the same pattern of results in the investigation of event-based prospective memory (Harris & Cumming, 2003; Harris & Menzies, 1999; but see Nigro & Cicogna, 1999). Conversely, the deleterious influence of depression on timebased prospective memory performance fits in well with the Resource Allocation Model by Ellis and Ashbrook (1988). Our results provided further evidence that the ability to carry out time-based intended actions seems to suffer when individuals are in depressive emotional states. According to Ellis and Ashbrook, depressed mood leads to a reduction in overall cognitive capacity and to the allocation of some attentional resources to task-irrelevant or depression-related thoughts. While this diminishment in attentional resources was not evident in the ongoing task, the time-based prospective memory task was susceptible to the adverse influences of depression, presumably because the time-based task required a high degree of self-initiated, effortful processing; and effortful processing is thought to be diminished in depression (see Hartlage et al., 1993). However, it should be noted the traditional measures for the amount of attentional resources that is devoted to a time-based prospective memory task, i.e., the clock monitoring measures, failed to be significantly associated with levels of self-reported depression, although this association would be predicted by the Resource Allocation Model (Ellis & Ashbrook, 1988; see Kliegel, Jäger, et al., 2005). Nevertheless, the strongest of the non-significant correlations indicated that participants experiencing higher levels of depression made somewhat fewer clock checks. In sum, the predicted mech-

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anism of the depressed individuals’ diminished attentional resources that they devoted to the prospective memory task receives further – albeit relatively weak – support by the present findings. In conclusion, our finding regarding the timebased task is consistent with the Resource Allocation Model of Ellis and Ashbrook and with previous findings reporting the same pattern of results in the investigation of time-based prospective memory (Kliegel, Jäger, et al., 2005; Rude et al., 2005). One unresolved issue, however, is the question why in the laboratory session the event-based task was more sensitive for anxiety than for depression, and why the reverse association was true for the time-based task. A possible interpretation could be that the accurate and continuous monitoring of the ongoing task items, which is necessary for successful eventbased responding, might be particularly sensitive to anxiety, since anxious people are thought as disengaging some amount of attention from cognitive tasks to the scanning of the external environment for potential threat (Harris & Cumming, 2003). Thus, anxious individuals, but not depressed individuals, might pay relatively less attention to the monitoring of the ongoing task items resulting in worse event-based prospective memory performance. By contrast, the self-initiated and effortful activities, which are necessary for successful time-based responding (i.e., mainly the self-initiated clock checking), might be relatively more sensitive to depression, because depressed individuals are characterized as having diminished cognitive initiative and problems in effortful processing (e.g., Hartlage et al., 1993; Hertel & Hardin, 1990). Hence, depressed individuals, but not anxious individuals, might engage in relatively less self-initiated, controlled processing, which results in worse time-based prospective memory performance. However, it should be noted that these differential associations between performance in the prospective memory tasks and the levels of self-reported anxiety and depression were unexpected in the present study. In consequence, future studies are necessary that will explicitly test the hypothesis that event-based prospective memory tasks are particularly sensitive to anxiety, whereas time-based prospective memory tasks are more sensitive to depression. In the naturalistic prospective memory task, contrasting and unexpected results emerged relative to the results of the laboratory session. Specifically, individuals experiencing higher levels of anxiety or depression had higher success rates in the naturalistic task, which was the reverse pattern of that obtained in the laboratory6 . Hence, this finding seems to be contrary to the prediction that negative emotions might generally diminish the ability to carry out future intentions through the disruption of cognitive capacities. However, caution seems warranted regarding this expectation, since naturalistic prospective memory tasks are carried out in everyday life and are not under the control of the experimenter. Therefore, naturalistic tasks 6 Note that within the subset of 30 participants that performed both the laboratory-based and the naturalistic prospective memory tasks, the nature of the association of depression and anxiety with prospective memory performance was indeed reversed across the laboratory-based versus naturalistic tasks, since within this sample the correlations between anxiety or depression and event- or time-based prospective memory performance were all negative, −0.06 > rs(30) > −0.40, 0.738 > ps > 0.030.

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may not exclusively be influenced by the participants’ basic cognitive abilities, such as their working memory capacity, executive functioning, or speed of information processing, but also by other, non-cognitive factors such as the use of external memory aids, personality factors, or other influences. Indeed, in everyday life people show a high tendency towards using external memory aids to support the successful remembering of intended actions, such as using agendas, making lists, or using reminder notes (see Long, Cameron, Harju, Lutz, & Means, 1999). With respect to the findings of the present study, one tentative interpretation might be that individuals with heightened anxiety or depression were more highly motivated to perform well in sending back the letter to the experimenter. Support for this interpretation comes from Eysenck and Calvo’s (1992) theory, which posits that in highly anxious people the fear of adverse outcomes will lead to increased motivation and effort in a task situation. In a similar vein, Ellis and Ashbrook (1988) state that when a task has a high personal relevance, it is not likely that performance is impaired by depressive mood states. In consequence, it might be the case that individuals experiencing relatively high levels of anxiety and/or depression were more highly motivated to succeed in the naturalistic prospective memory task and thus performed better than their low-anxious and low-depressive counterparts (presumably through the use of more external reminders or internal rehearsal of the intention). It should be noted that the contrasting findings of the present study regarding the influence of negative emotions on laboratory-based versus naturalistic prospective memory performance resembles findings of studies within the developmental domain: Laboratory studies generally find that normal aging is associated with a decrement in the ability to prospectively remember. Conversely, studies applying naturalistic prospective memory tasks consistently report that older participants succeed better in executing intended actions in everyday life relative to their younger counterparts (see Henry et al., 2004, for a review). The same pattern of oppositional effects was found in the present study regarding the influence of negative emotions on prospective memory performance. Thus, in a similar vein as the explanations for why the developmental findings diverge across laboratory-based and naturalistic prospective memory tasks, we suggest that individual prospective memory performance in the laboratory more purely reflect basic differences in individual cognitive abilities, whereas individual differences in naturalistic prospective memory tasks are influenced by many factors besides cognitive abilities, such as personality and motivation factors or the use of external memory aids (cf. Cuttler & Graf, 2005). Clearly, further studies are necessary to characterize how the execution of intended actions differs depending on whether they are executed in everyday life or in the laboratory. With regard to the strength of our results, it should be noted that the present effect sizes regarding the association between the emotion variables and prospective memory performance are relatively small (i.e., the proportion of variance in prospective memory performance that was explained by the emotion variables ranged from 3.2% to 17.6% among the significant effects). However, this outcome might not be surprising since

the participants’ negative mood states were presumably of low to moderate intensity and were thus not very likely to exert strong effects on cognitive task performance (see Ellis & Ashbrook, 1988). However, given that reliable effects were obtained, they are nevertheless of high practical and theoretical interest, and even stronger effects are likely to be found in further studies using mood induction procedures (cf. Kliegel, Jäger, et al., 2005) or clinically affective disorders (cf. Rude et al., 1999). In terms of conclusions, the present study added to the restricted body of literature investigating the potential influences of negative emotions on the ability to carry out intended actions. In line with previous studies, we found that both anxiety and depression were associated with diminished prospective memory performance in the laboratory tasks. A novel finding was that event-based versus time-based tasks seem to be differentially sensitive to emotional variables, which should be tested in further studies. Moreover, the present study opened a new realm within the paradoxical findings of laboratory versus naturalistic studies on prospective memory (see Henry et al., 2004): We provided first evidence that the association between emotion variables and prospective memory performance might be reversed in everyday life relative to the laboratory situation, at least in some tasks. However, further research is clearly necessary to replicate our findings. VI. G ENERAL D ISCUSSION In the present paper, we review the available findings on the potential influences of negative emotions on the ability to prospectively remember. Furthermore, we have provided some new data that further disentangled the contribution of depression and anxiety on different types of prospective memory tasks. In the final two sections, we now discuss the findings of all studies reported in this review. Specifically, we aim at summarizing the general pattern of results that were obtained in the investigation of the relationship between negative emotions and prospective memory. Furthermore, we provide a tentative explanation for why results were not fully consistent across studies. Finally, we will suggest some directions for future research examining the connection between emotions and the cognitive ability to remember to carry out intentions in the future. Our review strongly suggests that emotional processes do indeed influence the accuracy and the way in which humans carry out intended actions. In more detail, the intuitive expectation that negative emotional states might interfere with the accurate prospective remembering is generally supported by the reported studies. Two studies have investigated the influence of unspecifically defined negative emotions on prospective remembering using questionnaires, without assessing actual prospective memory performance in the laboratory or in everyday life (Meacham & Kushner, 1980; Schmidt, 2004). These studies indicated that the probability, with which intended actions are executed when one is in a state of negative emotions (Schmidt, 2004) or feels very discomfortable with a given intention (Meacham & Kushner, 1980), is diminished relative to more emotionally neutral prospective memory situations.


However, the two studies differ in the putative mechanism that might underlie this relationship: Meacham and Kushner’s findings suggest that aversion-evoking intentions lead to a strong activation of these intentions in memory, such that they are highly likely to be remembered, but still not executed. Thus, one cannot speak of a true prospective memory failure in such cases, but nevertheless, the negative emotions that are involved increase the probability that the intended actions are not executed. By contrast, the findings of Schmidt rather suggest that being in highly negative emotional states leads to true failures of remembering to carry out future intentions, presumably because attention is withdrawn from the planned action that one has in mind. Note, however, that the report of Schmidt does not actually elucidate the mechanism by which negative emotional states might interfere with prospective memory performance. Nevertheless, the two studies provide evidence that negative emotions can disrupt prospective remembering, and importantly, the two studies suggest that this effect – which was more frequently examined in the laboratory than in naturalistic settings – seems to generalize to reallife. However, a possible limitation of both studies is that their findings rely on introspective and retrospective reports of participants. Thus, it is important to complement such findings through the actual administration of prospective memory tasks in order to obtain objective measures of performance and relate them to emotion variables. This latter approach has been applied in a further handful of studies that examined how the more specifically defined emotion of anxiety is related to prospective memory. Whereas two laboratory studies indicated that heightened anxiety may actually improve prospective memory performance (Cockburn & Smith, 1994; Nigro & Cicogna, 1999), two other laboratory studies suggested that anxiety is more likely to diminish prospective memory performance (Harris & Cumming, 2003; Harris & Menzies, 1999). Consistent with these latter findings, a study on subjective memory beliefs revealed that heightened anxiety specifically concerning memory situations is associated with lower prospective memory performance (McDonaldMiszczak, Gould, & Tychynski, 1999). Furthermore, in the present paper we reported some new data revealing that in the laboratory, higher levels of anxiety were associated with worse (event-based) prospective memory performance, but in the naturalistic prospective memory task, individuals with higher levels of experienced anxiety actually showed better performance. Hence, the findings regarding the influence of anxiety on prospective remembering seem to be somewhat inconsistent. However, several possible explanations might be given for the discrepant results, especially for those results that seem to be inconsistent with a prediction that anxiety might have deleterious effects on prospective remembering (Eysenck & Calvo, 1992). First, the contrasting findings reported by Cockburn and Smith (1994) were already interpreted by other authors (i.e., Harris & Menzies, 1999) as possibly resulting from the high salience of the prospective memory task of that study. Specifically, as the appropriate moment for executing the intended action was signalled by a highly salient cue (i.e., an alarm), the prospective memory task presumably attracted the primary

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(rather than the secondary) allocation of attentional resources. Therefore, the execution of the intended action was not likely to be disrupted by anxiety, since the Processing Efficiency Theory (Eysenck & Calvo, 1992) predicts that the deleterious effects of anxiety more likely emerges in tasks treated as secondary rather than primary. By contrast, the motivational effects of anxiety might have played an important role in the Cockburn and Smith study: High-anxious participants might have spent greater effort towards the prospective memory task than, which apparently resulted in better performance relative to participants experiencing intermediate levels of anxiety. Second, the contrasting results of Nigro and Cicogna (1999) may also be reinterpreted within Eysenck and Calvo’s (1992) framework. Crucially, it seems that Nigro and Cicogna’s ongoing task was relatively undemanding. Thus, a deleterious effect of anxiety on the individuals’ attentional resources was not likely to emerge. By contrast, the motivational effects – rather than the attentional effects – of anxiety might again have played an important role: The presumed higher motivation of anxious people to perform well could have enhanced the latency of their prospective memory responses relative to less anxious participants, particularly because there probably emerged no adverse attentional effect of anxiety. As noted in the discussion of the novel data that were presented in this paper, the findings that heightened anxiety improved performance in the naturalistic prospective memory task (rather than disrupting it) could be explained by several factors, such as the lack of experimental control, the possibility to apply external memory aids, or again the motivational effect of anxiety resulting in increased motivation to perform well in the task (see Eysenck & Calvo, 1992). To summarize, the available findings on the relationship between anxiety and prospective memory performance revealed a complex pattern of results, with anxiety improving prospective memory performance under some circumstances, whereas leading to diminished performance in other situations. This pattern is thus consistent with Eysenck and Calvo’s (1992) notion that anxiety may either enhance or adversely affect cognitive task performance depending on the specific task characteristics. One of the most crucial factors determining the nature of this relationship seems to be the amount of cognitive capacity that is taken up by a task at hand. In situations where the ongoing activity and/or the prospective memory task are relatively undemanding (Cockburn & Smith, 1994; Nigro & Cicogna, 1999) or where the prospective memory task is in the focus of primary attention (Cockburn & Smith, 1994), adverse effects of anxiety might not be expected; by contrast, the effect of anxiety might even benefit prospective remembering in such situations because of the motivational effects of anxiety (Eysenck & Calvo, 1992). On the other hand, where the ongoing activity and/or the prospective memory task are strongly resource-demanding or where the prospective memory task is not in the focus of primary attention (Harris & Cumming, 2003; Harris & Menzies, 1999; the present eventbased task; see also McDonald-Miszczak et al., 1999), the diminished working memory capacity of anxious individuals as per Eysenck and Calvo might disrupt performance in the prospective memory task.

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Turning to the studies that examined how depression or depressive emotional states are related to prospective memory, the pattern of results reveals a multifaceted pattern across the few studies as well: In two of the studies, depressive emotions clearly had adverse effects on prospective memory performance (Kliegel, Jäger, et al., 2005; Rude et al., 1999), as would be expected by the Resource Allocation Model of Ellis and Ashbrook (1988). By contrast, other studies found no (Cockburn & Smith, 1994 – see Footnote 1; Livner et al., 2005) or only a relatively weak (Harris & Menzies, 1999) negative influence of depression on the ability to carry out intended actions. The novel findings that we reported in this paper seem to confirm that depression might interfere with some prospective memory tasks (i.e., with the timebased task). However, we also found that an event-based prospective memory task was not influenced by depression and that in a naturalistic task there was even a trend of improved performance in depressed individuals. Therefore, the question arises how the discrepant results can be explained. One possibility might be that depressive emotional states exert a relatively specific adverse effect on time-based prospective remembering, but not on event-based prospective remembering. This could be the case because time-based tasks generally involve a higher degree of self-initiated, controlled processing than many event-based tasks, which, in turn, are believed to rely on relatively automatic processes (e.g., d’Ydewalle et al., 2001); and crucially, depression has been shown to selectively disrupt self-initiated, effortful processes, but not automatic cognitive processes (see Hartlage et al., 1993, for a review). Indeed, the available pattern of results shows that where adverse effects of depressive emotional states were found (Kliegel, Jäger, et al., 2005; Rude et al., 1999), a time-based prospective memory task was applied, whereas event-based prospective memory tasks were administered in studies that found no or only weak influences of depression on prospective memory performance (Cockburn & Smith, 1994; Harris & Menzies, 1999; Livner et al., 2005). In addition, the novel data that are presented in this paper provided direct evidence that performance in a time-based task was influenced by depression, but not performance in an eventbased task. In conclusion, our review indicates that depressive emotional states interfere with prospective remembering, but only in tasks that require a high degree of self-initiated, controlled processes, such as time-based prospective memory tasks. However, it can be assumed that this will also hold for event-based tasks that are relying on more strategic processes, as a recent theoretical model, the multiprocess framework, of McDaniel and Einstein (2000) would predict. Especially, as the underlying mechanism of this depression-related deficit in prospective remembering seems to be a diminished amount of cognitive capacity or attentional resources that are allocated to a given prospective memory task (Ellis & Ashbrook, 1988; see Kliegel, Jäger, et al., 2005). One unresolved issue is the outcome of the presently reported novel data that in the naturalistic prospective memory task, a higher level of depressive symptoms was associated with better prospective memory performance – a pattern that was not observed before. Potential explanations for this result

are provided in the Discussion section above. Clearly, further studies are necessary to shed more light on the potential influences of depression on different types of prospective memory tasks. In concluding the present review, we suggest that the currently available findings provide evidence for the assumption that in general negative emotions have adverse effects on the accurate execution of intended actions, both in the laboratory and in everyday life, although this effect is sometimes absent or even reversed depending on a complex pattern of influencing factors. One of the most crucial factors seems to be the amount of cognitive capacity that is taken up by a task at hand. In situations where the ongoing activity and/or the prospective memory task are relatively undemanding, adverse effects of negative emotions might not be expected. This is certainly the case in many real-life situations, where the ongoing activity is often not overwhelmingly resource-demanding. Moreover, in everyday life people use external memory aids to support the timely and accurate remembering of intended actions. Thus, other factors than pure cognitive abilities play an important role for prospective memory processes in everyday life, which are also of relevance for the execution of intended actions under the influence of negative emotions. Nevertheless, in real-life situations where individuals are required to engage in relatively challenging ongoing activities – which is obviously the case in many work settings – and where the use of conspicuous external memory aids is not easily possible, the effects of negative emotions might generally be adverse and result in failures or inaccurate performance in prospective memory situations. Further studies are clearly necessary to extend the relatively restricted knowledge that we have on how the persuasive ability of prospective remembering is influenced by fluctuations in mood, by the emotional valence that we associate with specific intended action, or by clinically relevant affective disorders. VII. S OME D IRECTIONS FOR F UTURE R ESEARCH Throughout the present paper, we have already noted some issues that future studies might address to further promote our knowledge on emotional influences on prospective remembering. In this final section, some further issues are suggested that we propose should become the focus of future studies on emotion and prospective memory. First of all, we would like to mention a methodological issue that researchers might wish to consider in the examination of emotional influences on prospective memory: Some of the studies reported in this review used single-trial prospective memory tasks, that is, tasks that involved only one single trial in which the intended action was to be executed (Cockburn & Smith, 1994; Livner et al., 2005; the present naturalistic task). However, as Maylor (1993, 1996) pointed out, such singletrial observations have the disadvantage that they result in relatively unreliable measures of prospective memory, which apparently makes it difficult to investigate the relationship between prospective memory performance and emotion variables. Thus, we suggest that future studies should try to avoid using single-trial tasks in order to obtain more reliable


measures of prospective memory performance (such as in the studies of e.g., Harris & Cumming, 2003; Rude et al., 1999). Most of the previous studies have investigated how the emotional state of participants influenced their ability to prospectively remember (e.g., Harris & Menzies, 1999; Kliegel, Jäger, et al., 2005; Rude et al., 1999; Schmidt, 2004). By contrast, we are aware of only one study that investigated how prospective memory performance is modulated by the emotional valence that is attributed to the specific intended action (Meacham & Kushner, 1980). Hence, future studies should more systematically investigate how the emotional appraisal of a prospective memory task influences the outcome in this task. For instance, researchers could experimentally manipulate the affective tone of intended actions in a controlled laboratory experiment (which, admittedly, might require an ingenious paradigm) in order to examine how the probability of executing an intended action is influenced by the degree to which one feels comfortable or discomfortable with a specific intention that is to be executed. A complementary approach would be to manipulate the emotional appraisal of the ongoing task. For instance, it might be expected that intended actions are less likely to be executed when one is engaged in a highly pleasant ongoing task. A further and important avenue for future studies is to extend the investigation of emotional influences on prospective remembering to positive emotions (e.g., elation, happiness, comfort, etc.), particularly because positive versus negative affects seem to change the style in which cognition operates in an asymmetrical manner (see Kuhl & Kazén, 1999). Previous studies showed that positive mood reliably enhances planning processes (Oaksfoard, Morris, Grainger, & Williams, 1996; Phillips, Smith, & Gilhooly, 2002); and planning abilities are assumed to be of high relevance for the successful execution of intended actions (e.g., Kliegel et al., 2002). Moreover, positive affect seems to release the inhibition of the pathway between stored intentions and their (motor) output systems thereby possibly facilitating the execution of an intended action (Kuhl & Kazén, 1999). In consequence, one might expect a positive relationship between positive emotions and prospective memory performance. However, the exact nature of this potential relationship needs to be elucidated in future studies. A prominent issue that could be investigated by further studies is the observation that the effects of negative emotions on prospective memory performance seem to strongly interact with the amount of cognitive resources that are required for a particular task. As Eysenck and Calvo (1992) point out, anxiety generally has a positive motivational effect, which renders performance of highly anxious people better than performance of their less anxious counterparts in tasks that place relatively little demands on the cognitive system. By contrast, in highly demanding task situations performance declines in highly anxious people because of the attentional effect of anxiety. With regard to depression, it is not assumed that depressed people have a higher motivation than their non-depressed counterparts. Thus, depression should be associated with either spared or diminished, but not with increased prospective memory performance, depending on the specific task characteristics.

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In consequence, future studies might test the following hypothesis: In undemanding ongoing/prospective memory tasks, highly anxious participants should perform better than less anxious people, whereas highly depressed participants might only show spared or even slightly diminished performance. By contrast, in highly demanding ongoing/prospective memory tasks, both anxiety and depression should result in worse performance in the ongoing/prospective memory task relative to an emotionally more neutral baseline. Therefore, future studies should introduce manipulations of the difficulty of the ongoing/prospective memory tasks in the investigation of emotional factors on prospective remembering. This approach might be helpful in discovering further differences between the processes underlying anxiety- and depression-mediated effects on cognitive performance (see Eysenck & Calvo, 1992; Harris & Menzies, 1999; Hartlage et al., 1993). One further important issue is to oppose emotional influences on prospective memory situations in the laboratory and in everyday life, especially because there is little information on how inner-states of positive or negative emotions are related to the execution of intended actions in everyday life (but cf. Ellis & Nimmo-Smith, 1993). The study that we reported in the present paper suggests that emotional influences on prospective remembering might be contrary in laboratory-based versus naturalistic prospective memory tasks, in a similar vein as the paradoxical findings that emerged within the developmental domain of prospective memory research (see Henry et al., 2004). Thus, future studies should shed more light on how emotion variables affect prospective remembering in real-life and in the experimenter-controlled laboratory situation. Given the restricted body of literature investigating how the highly relevant cognitive ability to prospectively remember is subject to emotional influences, a plethora of other issues are imaginable that might be addressed in future studies. Our suggestion is that the elucidation of this relationship might have both theoretical relevance by advancing our knowledge how cognition and emotion are interconnected as well as considerable practical relevance by revealing how the emotional valence of intended actions, transient fluctuations in mood, enduring emotional states, or clinically relevant affective disorders can modulate the execution of intended actions in everyday life. R EFERENCES [1] Albersnagel, F. A. (1988). Velten and musical mood induction procedures: A comparison with accessibility of thought associations. Behavior Research and Therapy, 26, 79-96. [2] Asberg, M. & Shalling, D. (1979). Construction of a new psychiatric rating instrument, the Comprehensive Psychopathological Rating Scale (CPRS). Progress in Neuro-Psychopharmacology, 3, 405-412. [3] Baddeley, A. D. (1990). Human memory: Theory and practice. Hove: Lawrence Erlbaum Associates. [4] Bjelland, I., Dahl, A. A., Haug, T. T., & Neckelmann, D. (2002). The validity of the Hospital Anxiety and Depression Scale – An updated literature review. Journal of Psychosomatic Research, 52, 69-77. [5] Blaney, P. H. (1986). Affect and memory: A review. Psychological Bulletin, 99, 229-246. [6] Bower, G. H., Montiero, K. P., & Gilligan, S. G. (1978). Emotional mood as a context for learning and recall. Journal of Verbal Learning and Verbal Behavior, 17, 573-585.

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[7] Brandimonte, M. A., Einstein, G. O., & McDaniel, M. A. (Eds.) (1996). Prospective memory: Theory and applications. Mahwah, NJ: Lawrence Erlbaum Associates Inc. [8] Burt, D. B., Zembar, M. J., & Niederehe, G. (1995). Depression and memory impairment: A meta-analysis of the association, its pattern, and specificity. Psychological Bulletin, 117, 285-305. [9] Clore, G. L. & Martin, L. L. (2001). Introduction. In L. L. Martin & G. L. Clore (Eds.), Theories of mood and cognition: A user’s guidebook (pp. 1-7). Mahwah, NJ: Lawrence Erlbaum Associates Inc. [10] Cockburn, J. & Smith, P. T. (1994). Anxiety and errors of prospective memory among elderly people. British Journal of Psychology, 85, 273282. [11] Crovitz, H. F. & Daniel, W. F. (1984). Measurements of everyday memory: Toward the prevention of forgetting. Bulletin of the Psychonomic Society, 22, 413-414. [12] Cuttler, C. & Graf, P. (2005, July). Personality and cognitive ability underlie age-related differences in prospective memory. Poster presented at the 2nd International Conference on Prospective Memory in Zurich, Switzerland. [13] d’Ydewalle, G., Bouckaert, D., & Brunfaut, E. (2001). Age-related differences and complexity of ongoing activities in time- and event-based prospective memory. American Journal of Psychology, 114, 411-423. [14] Einstein, G. O. & McDaniel, M. A. (1990). Normal aging and prospective memory. Journal of Experimental Psychology: Learning, Memory, and Cognition, 16, 717-726. [15] Einstein, G. O. & McDaniel, M. A. (1996). Retrieval processes in prospective memory: Theoretical approaches and some new findings. In M. Brandimonte, G. O. Einstein, & M. A. McDaniel (Eds.), Prospective memory: Theory and applications (pp. 115-142). Mahwah, NJ: Erlbaum. [16] Einstein, G. O., McDaniel, M. A., Richardson, S. L., Guynn, M. J., & Cunfer, A. R. (1995). Aging and prospective memory: Examining the influences of self-initiated retrieval processes. Journal of Experimental Psychology: Learning, Memory, and Cognition, 21, 996-1007. [17] Ellis, H. C. (1991). Focused attention and depressive deficits in memory. Journal of Experimental Psychology: General, 120, 310-312. [18] Ellis, J. (1996). Prospective memory or the realization of delayed intentions: A conceptual framework for research. In M. Brandimonte, G. O. Einstein, & M. A. McDaniel (Eds.), Prospective memory: Theory and applications (pp. 1-22). Mahwah, NJ: Erlbaum. [19] Ellis, H. C. & Ashbrook, P. W. (1988). Resource allocation model of the effects of depressed mood states on memory. In K. Fiedler & J. Forgas (Eds.), Affect, cognition, and social behaviour (pp. 25-43). Toronto: Hogrefe. [20] Ellis, J. & Kvavilashvili, L. (2000). Prospective memory in 2000: Past, present, and future directions. Applied Cognitive Psychology, 14, 1-9. [21] Ellis, J. A. & Nimmo-Smith, I. (1993). Recollecting naturally-occurring intentions: A study of cognitive and affective factors. Memory, 1, 107126. [22] Eysenck, M. W. & Calvo, M. G. (1992). Anxiety and performance: The processing efficiency theory. Cognition and Emotion, 6, 409-434. [23] Gerrards-Hesse, A., Spies, K., & Hesse, F. W. (1994). Experimental inductions of emotional states and their effectiveness: A review. British Journal of Psychology, 85, 55-78. [24] Harris, L. M. & Cumming, S. R. (2003). An examination of the relationship between anxiety and performance on prospective and retrospective memory tasks. Australian Journal of Psychology, 55, 51-55. [25] Harris, L. M. & Menzies, R. G. (1999). Mood and prospective memory. Memory, 7, 117-127. [26] Hartlage, S., Alloy, L. B., Vazquez, C., & Dykman, B. (1993). Automatic and effortful processing in depression. Psychological Bulletin, 113, 247278. [27] Henry, J. D., MacLeod, M. S., Phillips, L. H., & Crawford, J. R. (2004). A meta-analytic review of prospective memory and aging. Psychology and Aging, 19, 27-39. [28] Herrmann, C. (1997). International experiences with the Hospital Anxiety and Depression Scale – A review of validation data and clinical results. Journal of Psychosomatic Research, 42, 17-41. [29] Hertel, P. T. & Hardin, T. S. (1990). Remembering with and without awareness in a depressed mood: Evidence of deficits in initiative. Journal of Experimental Psychology: General, 119, 45-59. [30] Hertel, P. T. & Milan, S. (1994). Depressive deficits in recognition: Dissociation of recollection and familiarity. Journal of Abnormal Psychology, 103, 736-742. [31] Isen, A. M., Shalker, T. E., Clark, M., & Karp, L. (1978). Affect, accessibility of material in memory, and behavior: A cognitive loop? Journal of Personality and Social Psychology, 36, 1-12.

[32] Jäger, T. & Kliegel, M. (submitted). Time-based and event-based prospective memory across adulthood: Underlying mechanisms and differential costs on the ongoing task. [33] Kensinger, E. A. & Corkin, S. (2003). Effect of negative emotional content on working memory and long-term memory. Emotion, 3, 378393. [34] Kliegel, M., Horn, A. B., & Zimmer, H. (2003). Emotional after-effects on the P3 component of the event-related brain potential. International Journal of Psychology, 38, 129-137. [35] Kliegel, M. & Jäger, T. (in press). Delayed-execute prospective memory performance: The effects of age and working memory. Developmental Neuropsychology. [36] Kliegel, M., Jäger, T., & Phillips, L. H. (under revision). Emotional development across adulthood: Differential age-related emotional reactivity and emotion regulation in a negative mood induction procedure. [37] Kliegel, M., Jäger, T., Phillips, L. H., Federspiel, E., Imfeld, A., Keller, M., & Zimprich, D. (2005). Effects of sad mood on time-based prospective memory. Cognition and Emotion, 19, 1199-1213. [38] Kliegel, M. & Martin, M. (2003). Prospective memory research: Why is it relevant? International Journal of Psychology, 38, 193-194. [39] Kliegel, M., Martin, M., McDaniel, M. A., & Einstein, G. O. (2001). Varying the importance of a prospective memory task: Differential effects across time- and event-based prospective memory. Memory, 9, 1-11. [40] Kliegel, M., Martin, M., McDaniel, M. A., & Einstein, G. O. (2002). Complex prospective memory and executive control of working memory: A process model. Psychologische Beiträge, 44, 303-318. [41] Kliegel, M., McDaniel, M. A., & Einstein, G. O. (Eds.) (in press). Prospective memory: Cognitive, neuroscience, developmental, and applied perspectives. Mahwah, NJ: Lawrence Erlbaum Associates Inc. [42] Kliegel, M., Phillips, L. H., Lemke, U., & Kopp, U. A. (2005). Planning and realisation of complex intentions in patients with Parkinson’s disease. Journal of Neurology, Neurosurgery, and Psychiatry, 76, 15011505. [43] Kuhl, J. & Kazén, M. (1999). Volitional facilitation of difficult intentions: Joint activation of intention memory and positive affect removes Stroop interference. Journal of Experimental Psychology: General, 128, 382-399. [44] Kvavilashvili, L., Messer, D. J., & Ebdon, P. (2001). Prospective memory in children: The effects of age and task interruption. Developmental Psychology, 37, 418-430. [45] Lehrl, S., Merz, J., Burkhard, G., & Fischer, S. (1991). Der Mehrfachwahl-wortschatztest MWT-A. Göttingen: Hogrefe. [46] Livner, A., Berger, A.-K., Jones, S., & Bäckman, L. (2005, July). Effects of depression on prospective and retrospective memory functioning among elderly adults. Poster presented at the 2nd International Conference on Prospective Memory in Zurich, Switzerland. [47] Long, T. E., Cameron, K. A., Harju, B. L., Lutz, J., & Means, L. W. (1999). Women and middle-aged individuals report using more prospective memory aids. Psychological Reports, 85, 1139-1153. [48] Lovibond, S. H. & Lovibond, P. F. (1995). The structure of negative emotional states: Comparison of the depression anxiety stress scales (DASS) with the Beck depression and anxiety inventories. Behaviour, Research, and Therapy, 3, 335-343. [49] Martin, M. (1986). Aging and patterns of change in everyday memory and cognition. Human Learning, 5, 63-74. [50] Martin, M. (1990). On the induction of mood. Clinical Psychology Review, 10, 669-697. [51] Martin, L. L. & Clore, G. L. (Eds.) (2001). Theories of mood and cognition: A user’s guidebook. Mahwah, NJ: Lawrence Erlbaum Associates Inc. [52] Martin, M., Kliegel, M., & McDaniel, M. A. (2003). The involvement of executive functions in prospective memory performance of adults. International Journal of Psychology, 38, 195-206. [53] Maylor, E. A. (1993). Aging and forgetting in prospective and retrospective memory tasks. Psychology and Aging, 8, 420-428. [54] Maylor, E. A. (1996). Age-related impairment in an event-based prospective-memory task. Psychology and Aging, 11, 74-78. [55] Maylor, E. A., Smith, G., Della Sala, S., & Logie, R. H. (2002). Prospective and retrospective memory in normal aging and dementia: An experimental study. Memory & Cognition, 30, 871-884. [56] McDaniel, M. A. & Einstein, G. O. (2000). Strategic and automatic processes in prospective memory retrieval: A multiprocess framework. Applied Cognitive Psychology, 14, 127-144. [57] McDonald-Miszczak, L., Gould, O. N., & Tychynski, D. (1999). Metamemory predictors of prospective and retrospective memory performance. The Journal of General Psychology, 126, 37-52.


[58] Meacham, J. A. & Kushner, S. (1980). Anxiety, prospective remembering and performance of planned actions. Journal of General Psychology, 103, 203-209. [59] Nigro, G. & Cicogna, P. (1999). Comparison between time-based and event-based prospective memory tasks. Ricerche di Psicologia, 3, 55-68. [60] Oaksford, M., Morris, F., Grainger, B., & Williams, J. M. G. (1996). Mood, reasoning, and central executive processes. Journal of Experimental Psychology: Learning,Memory, and Cognition, 22, 477–493. [61] Patton, G. W. & Meit, M. (1993). Effect of aging on prospective and incidental memory. Experimental Aging Research, 19, 165-176. [62] Phillips, L. H., Smith, L., & Gilhooly, K. J. (2002). The effects of adult aging and induced positive and negative mood on planning. Emotion, 2, 263-272. [63] Rendell, P. G. & Thomson, D. M. (1993). The effect of ageing on remembering to remember: An investigation of simulated medication regimens. Australian Journal on Ageing, 12, 11-18. [64] Rendell, P. G. & Thomson, D. M. (1999). Aging and prospective memory: Differences between naturalistic and laboratory tasks. The Journals of Gerontology: Psychological Sciences, 54B, 256-269. [65] Rude, S. S., Hertel, P. T., Jarrold, W., Covich, J., & Hedlund, S. (1999). Depression-related impairments in prospective memory. Cognition and Emotion, 13, 267-276. [66] Schmidt, S. R. (2004). Autobiographical memories for the September 11th attacks: Reconstructive errors and emotional impairment of memory. Memory and Cognition, 32, 443-454. [67] Snodgrass, J. G. & Vanderwart, M. (1980). A standardized set of 260 pictures: Norms for name agreement, image agreement, familiarity, and visual complexity. Journal of Experimental Psychology: Human Learning and Memory, 6, 174-215. [68] Spielberger, C. D., Gorsuch, R. L., & Lushene, R. E. (1983). Manual for the State-Trait Anxiety Inventory. Palo Alto, CA: Consulting Psychologists Press. [69] Smith, R. E. & Bayen, U. J. (2004). A multinomial model of event-based prospective memory. Journal of Experimental Psychology: Learning, Memory, and Cognition, 30, 756-777. [70] Steyer, R., Schwenkmezger, P., Notz, P., & Eid, M. (1994). Theoretical analysis of a multidimensional mood questionnaire (MDBF). Diagnostica, 40, 320-328. [71] Steyer, R., Schwenkmezger, P., Notz, P., & Eid, M. (1997). Der Mehrdimensionale Befindlichkeitsfragebogen (MDBF). Göttingen: Hogrefe. [72] Terry, W. S. (1988). Everyday forgetting: Data from a diary study. Psychological Reports, 62, 299-303. [73] Wechsler, D. (1987). Wechsler Memory Scale, Revised (WMS-R) Manual. San Antonio, TX, USA: Psychological Corp. [74] Wilson, B. A., Cockburn, J., & Baddeley, A. D. (1985). The Rivermead Behavioural Memory Test. Bury St. Edmunds: Thames Valley Test Co. [75] Zigmond, A. S. & Snaith, R. P. (1983). The Hospital Anxiety and Depression Scale. Acta Psychiatrica Scandinavica, 67, 361-370.

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