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The fate of previously focused working memory content: Decay or/and inhibition?

Johannes Großer & Markus Janczyk Department of Psychology III University of Würzburg

Working memory is thought to allow short term storage of information in a state in which this information can be manipulated by ongoing cognitive processes. Evidence from various paradigms suggests that at any time only one item held in working memory is selected for possible manipulation. Oberauer (2002) has thus suggested a 1-item focus of attention within his model of working memory. Conceivably, this focus of attention needs to shift between several items during task performance and the following question is unresolved: What happens to a formerly selected, but now de-selected, item? Several studies have addressed this question, with opposing results. Bao, Li, Chen, and Zhang (2006) investigated verbal working memory with an updating task where participants count the number of occurrences of (three) different sequentially presented geometric objects (e.g., Garavan, 1998; see also Janczyk & Grabowski, 2011). In particular, they employed the logic typically used to show n-2 repetition costs in task-switching experiments and found slower updating in ABA than in CBA sequences, i.e., evidence for an active inhibition of de-selected items (but see Janczyk, Wienrich, & Kunde, 2008, for no signs of inhibition with a different paradigm). Rerko and Oberauer (2013) investigated visual working memory with the retrocue paradigm. Participants first learned an array of briefly presented colored items. Long after encoding, one, two, or three retro-cues (arrows) were presented one after another, with always the last one pointing to the particular location that is subsequently tested with a change detection task. (The retro-cue effect refers to the finding of improved performance after valid compared with neutral cues.) In the critical condition, Rerko and Oberauer presented three retro-cues to employ the n-2 repetition logic and found evidence for passive decay of deselected items. These diverging results obviously come with many differences between experiments: verbal vs. visual working memory, three working items vs. six working items, two different groups of participants, and so on. Here we present ongoing work aiming at identifying the critical factor(s). As a first step, we attempted to replicate the results of Bao et al. (2006) and Rerko and Oberauer (2013) within one sample of participants. A group of n = 24 students took part in two experiments (we excluded participants with less than 65% correct trials; 10 in Exp. 1 / 3 in Exp. 2). In Experiment 1, participants performed in a three-objects updating task and we compared performance in ABA and CBA trials. ABA trials yielded longer RTs (see Fig. 1, 1

left panel), thus pointing to inhibitory mechanisms just as Bao et al. (2006) reported. In Experiment 2, participants performed in a retro-cue task with 1, 2, or 3 retro-cues presented one after another. Most importantly, in the “3 retro-cue condition” the cues either pointed to three different locations (CBA) or the first and the third cue pointed to the same location (ABA). We did not observe a difference in accuracy in this case, but RTs were longer in CBA than in ABA trials (see Fig. 1, right panel), thus pointing to passive decay but not to inhibitory mechanisms.

Figure 1: Response times (RT) in milliseconds (ms) of Experiments 1 and 2 as a function of trial sequence (CBA [control] vs. ABA [inhibition]).

After all, with one single sample of participants we were able to largely replicate the diverging results from two tasks that were designed to answer the same research question. Given this, it appears worthwhile to us to continue this work and to isolate critical factors. This work is currently in progress. References: Bao M, Li ZH, Chen XC, Zhang DR (2006) Backward inhibition in a task of switching attention within verbal working memory. Brain Res Bull 69: 214-221. Garavan H (1998) Serial attention within working memory. Mem Cognition 26: 263-276. Janczyk M, Grabowski J (2011) The focus of attention in working memory: Evidence from a word updating task. Memory 19: 211-225. Janczyk M, Wienrich C, Kunde W (2008) On the costs of refocusing items in working memory: A matter of inhibition or decay? Memory 16; 374-385. Oberauer K (2002) Access to information in working memory: Exploring the focus of attention. J Exp Psychol Learn 28: 411-421. Rerko, L., & Oberauer, K. (2013). Focused, unfocused, and defocused information in working memory. J Exp Psychol Learn : 39 1075-1096. 2