This is a close-to-final draft of this article. The final version can be found at: Camachon, C., Jacobs, D. M., Huet, M., Buekers, M., & Montagne, G. (2007). The role of concurrent feedback in learning to walk through sliding doors. Ecological Psychology, 19, 367382.
Concurrent feedback and learning
The role of concurrent feedback in learning to walk through sliding doors
Cyril Camachon 1, David M. Jacobs1, Mickaël Huet1, Martinus Buekers2, and Gilles Montagne 1
1
UMR Mouvement et Perception
Université de la Méditerranée et CNRS 2
Department of Kinesiology
Katholieke Universiteit Leuven, Belgium
Correspondence should be addressed to: Gilles Montagne Université de la Méditerranée, Faculté des Sciences du Sport UMR Mouvement et Perception 163 Avenue de Luminy 13009 Marseille, France Phone number 33 (0)491172273 Fax number 33 (0)491172252 (e-mail :
[email protected])
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Concurrent feedback and learning
Abstract Concurrent feedback is defined as information about performance given to participants during the execution of an action. The present article investigates whether concurrent feedback is beneficial or detrimental to the learning of an ecologically relevant task. Eighteen participants were asked to walk through a virtual corridor and they practiced over 1110 trials to adjust their walking speed so as to pass through sliding doors that opened and closed at a frequency of 1 Hz. Concurrent feedback informed them about the possible need to accelerate or decelerate. Performance of participants who received concurrent feedback on 66% of the practice trials (on average) did not differ significantly from performance of participants who did not receive concurrent feedback. Furthermore, participants of both of these groups significantly outperformed participants who received concurrent feedback on all practice trials. These results are discussed in relation to the perceptual-motor mechanisms that underlie the control of the action. Also discussed are implications for future research, including the use of self-controlled feedback and the use of multisensory training programs.
Keywords: optical information; perception-action coupling; goal-directed displacement; virtual reality, concurrent feedback, education of attention
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Concurrent feedback and learning
The role of concurrent feedback in learning to walk through sliding doors
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Concurrent feedback and learning 1
Introduction Virtually all perceptual-motor skills improve with practice and such improvements are
crucially important to adaptive behavior. Learning is therefore an interesting and important research topic for proponents of ecological and non-ecological theories alike. Two largely independent lines of learning research are the often non-ecological study of the beneficial and/or detrimental effects of different types of knowledge of results (e.g., Salmoni, Schmidt, & Walter, 1984) and the more ecological study of the education of attention (e.g., Gibson, 1979; Gibson & Gibson, 1955). Although the ecological approach departs on important aspects from the aforementioned literature on feedback and knowledge of results (cf. Fowler & Turvey, 1978; Newell & Walter, 1981), other aspects might be usefully applied in ecological settings and be given ecological interpretations. The present study, then, addresses the notion of concurrent feedback in an ecological context. Let us first briefly review the ecological approach to learning and the relevant knowledge about concurrent feedback. The ecological approach to learning has recently received a renewal of interest (e.g., Fajen, 2005; Jacobs & Michaels, 2007; Michaels & de Vries, 1998; Montagne, Buekers, Camachon, de Rugy, & Laurent, 2003). Following Gibson’s proposal (1966, 1979), the education of attention towards the more useful sources of information has been shown to be an important aspect of learning. This attunement process has been observed in various tasks, such as judging the relative mass of colliding balls (Jacobs, Runeson, & Michaels, 2001; Runeson, Juslin, & Olsson, 2000), initiating the release of a pendulum in an interceptive task (Smith, Flach, Dittman, & Stanard, 2001), and emergency braking (Fajen & Devaney, 2006). Overall, these studies demonstrate a shift in which informational variable is used to perform the task, from sources of
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Concurrent feedback and learning information weakly correlated to the event under consideration (e.g., the relative mass of the balls) to sources of information highly correlated or even specific to that event. These studies have also asked whether the attunement process can be facilitated, and they have indicated that the attunement depends on various parameters such as the conditions of practice and the success criterion (cf., Tresilian, 1999). Fajen and Devaney (2006), for example, showed that if the success criterion is low enough to allow participants to succeed on the basis of weakly correlated sources of information, learning does not necessarily entail a convergence towards highly correlated ones. In addition, some conditions of practice facilitate convergence towards the more relevant source of information, whereas others impede this convergence (e.g., Fajen & Devaney, 2006; Smith et al., 2001). Relatedly, Jacobs et al. (2001) showed that the attention of learners can be directed towards the more relevant sources of information more rapidly by organizing practice in a way that judgments based on a non-optimal sources of information are systematically erroneous (the most successful practice condition was referred to as zero-correlation practice). In sum, there are several indications about how practice should be organized so that the (implicit or explicit) feedback most rapidly guides the attention of learners to the most optimal informational variables. The above-mentioned studies have in common that if participants received feedback, they received the feedback after the experimental trials. During the process of perceiving or acting, the only information available to them was the information in the natural ambient energy arrays or the simulated energy arrays aimed to replace these. No attempts were made to provide additional information to perceivers and actors while perceiving or acting. The present study addresses whether presenting additional information during the execution of an action affects learning.
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Concurrent feedback and learning From an ecological perspective one could refer to such information as enhanced information, but traditionally it has been referred to as concurrent feedback. To date several studies investigated the role of concurrent feedback, for instance in the learning of bimanual coordinations (Debeare, Wenderoth, Sunaert, Van Hecke, & Swinnen, 2003; Swinnen, Walter, Lee, & Serrien, 1993; Verschueren, Swinnen, Dom, & De Weerdt, 1997) and movement sequences (Park, Shea, & Wright, 2000; Schmidt & Wulf, 1997). These studies show that providing concurrent feedback has positive effects on performance. However, the beneficial effects often disappear in delayed retention tests, in which no concurrent feedback is provided (e.g., Schmidt & Wulf, 1997). This result has been explained with the guidance hypothesis (Salmoni, Schmidt, & Walter, 1984), according to which the more the feedback guides learners during practice, the more learners come to depend on the feedback. Hence, performance decreases on delayed retention tests that are performed without concurrent feedback. However, several studies emphasized a mediating role of feedback frequency; feedback dependency could be lessened if the concurrent feedback is provided only on a reduced number of trials. Park et al. (2000) addressed the frequency issue using a waveform-reproduction task. Participants in their study were asked to reproduce a force pattern represented by a waveform on a computer monitor. A first group of participants received concurrent feedback on each trial (100% group), a second group received concurrent feedback only on half the trials (50% group), and a third group served as control group and did not receive concurrent feedback at all. Reducing the frequency of the feedback from 100% to 50% improved learning. However, the control group obtained similar results as the 50% group during a retention test. Thus, decreasing the feedback frequency prevented participants from becoming feedback dependent, but the
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Concurrent feedback and learning concurrent feedback failed to increase the learning benefits beyond the performance level attained in the absence of the feedback. In the present study we address the role of concurrent feedback and the mediating effect of feedback frequency using a more ecologically relevant perceptual-motor task. On the basis of the previously reviewed results one might hypothesize that concurrent feedback is detrimental because of the guidance effect, even if feedback is not provided on each trial (e.g., Park et al., 2000). Concurrent feedback might also be beneficial if it guides the attention of learners towards the more optimal informational variables. There are additional reasons to believe that concurrent feedback is beneficial in the present task. To explain these reasons we first need to describe the task in more detail. Participants were asked to walk through a virtual corridor and to adjust their walking speed in order to pass through a pair of sliding doors, which opened and closed at a frequency of 1 Hz. The task was to pass the doors approximately at the moment of their widest aperture. Typical for this type of task is the close coupling between perception and action. Participants need to detect information about their current relation to the environment in order to change (or not) their walking speed and, as a result, pass the doors at the right time. Previous studies have shown that this is a difficult task (e.g., Buekers, Montagne, de Rugy, & Laurent, 1999; Montagne et al., 2003). Participants need an extensive practice period before they become attuned to the perceptual information that specifies the current relation to the environment (Camachon, Buekers, & Montagne, 2004; Camachon, Montagne, Buekers, & Laurent, 2004). Once this perception-action link is established participants succeed in the task by exhibiting adaptive changes in walking speed. The concurrent feedback provided in this study continuously informed the participants about the current relation to the environment (i.e., about the need to
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Concurrent feedback and learning accelerate, decelerate, or keep the walking speed unchanged). In visualizing the current relation, participant might be able to more readily access the sources of information that specify this relation. The concurrent feedback might also be beneficial with regard to a second learning process, which has been identified and described by Montagne et al. (2003). At intermediate stages of learning, learners almost exclusively decelerate to pass through the sliding doors. They decelerate even in cases in which a small acceleration would allow them to pass through the doors earlier and in an apparently more efficient way. Learning appears to exist partly of a transition to a strategy in which decelerating and accelerating become equally likely. One might hypothesize that concurrent feedback makes this transition easier. If participants sometimes pass through the sliding doors by accelerating instead of decelerating because the concurrent feedback informs them to accelerate, then they might sooner become familiar with the acceleration strategy, and also come to adopt it in the absence of concurrent feedback. In the light of the above-mentioned findings we think that it is worth examining whether concurrent feedback will reduce the amount of practice needed to learn this task. 2
Method 2.1
Participants
Eighteen students (mean age=26 years, SD=3.43) participated in the experiment. All participants had normal or corrected-to-normal vision. They were divided in three experimental groups of equal size (n=6). Participants had no experience with the experimental task and they were not informed about the purpose of the study. Informed consent was obtained prior to testing.
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Concurrent feedback and learning 2.2
Task
Participants were asked to proceed in a virtual straight corridor in order to pass through a pair of sliding doors that opened and closed at a frequency of 1 Hz. To this aim, participants moved forward by walking on a treadmill, allowing them to adjust their walking speed if needed. Lateral displacements were not permitted. The temporal window that allowed a correct door passing was 188 ms. Feedback indicating success or failure was provided by means of a green square (correct passing) or a red square (failure), projected in the centre of the screen immediately after each door passing. The purpose of this feedback was to replace the feedback normally available in real life (i.e., in real life participants would bump into the doors or be caught between them when they would arrive at the wrong moment). Hence, the success/failure feedback was provided on each door passing in each phase of the experiment, independently from the concurrent feedback that was provided (or not) in the acquisition phase. A next pair of doors appeared shortly after the moment at which the participant passed trough the previous doors; this means that only one pair of doors was visible at each time. 2.3
Apparatus
The virtual reality set-up (Figure 1) consisted of two PC Dell workstations (Optiplex GX240), a treadmill (Gymrol, Model BRL 1800), a Barcographics 808s projector, and a 2.3 m high by 3 m wide projection screen. The first PC workstation (control station) was responsible for the data acquisition and the real-time processing via an ADwin-Pro system (Keithley Inc.). The data of the treadmill were continuously fed back (200 Hz) to the control station. From these data, the computer calculated the positions of participants in the virtual environment and transmitted these to the second PC workstation (graphics workstation), which generated the modifications in the visual scene that were then projected on the screen within a delay of 30-50 ms. The visual
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Concurrent feedback and learning scene was projected onto the projection screen, placed 75 cm in front of participants, and was changed at a rate of 60 frames/s. ________________________ Insert Figure 1 about here. ________________________ Treadmill specificities. Participants walked on the treadmill’s moving belt, which was 0.6 m wide and 1.8 m long. They were attached to the framework of the treadmill by means of a belt that was fixed to a rotating axis via a rigid rod (Figure 1). To obtain reliable and realistic locomotor patterns, the initial speed of the moving belt was adjusted for each participant to allow the participant to overcome the friction forces exerted on the belt. This means that the force generated by the treadmill was chosen so that the force generated by the participant would result in a speed of the moving belt approximately equivalent to the speed produced by participants while walking on a normal surface. Participants were asked not to stop or run on the treadmill. The position of the treadmill was measured by means of an optical encoder at a frequency of 200 Hz, allowing us to calculate the position of the participant in the corridor to the nearest cm. Visual scene specificities. The visual scene consisted of successive corridors of 20 m long, 3 m wide, and 2.3 m high (Figure 2). In each of these corridors a pair of sliding doors was programmed at a random distance between 16 and 18.5 m from the entrance of the corridor. These doors opened and closed at a frequency of 1 Hz and with a speed of 1.5 m.s-1. This resulted in a maximal door aperture of 1.5 m (0.75 m for each door) every other second. All surfaces (walls, floor, ceiling, and doors) were textured to enhance the global flow field. 2.4
The Concurrent Feedback
Concurrent feedback was provided by a pair of triangles on a vertical reference bar, presented on the left of the visual scene (Figure 2). The middle part of the reference bar was 11
Concurrent feedback and learning green and the upper and lower parts were red. The red parts indicated that the participant would arrive early (upper part) or late (lower part) if the walking speed would remain constant. The green part indicated that the future door passing would be accurate. Thus, the bar provided information about the current error, defined as the error that would be observed at the door passing if the current walking speed would remain constant. Note that, if the walking speed changes during a trial, the current error changes accordingly. This means that participants were continuously informed about the ‘gap’ between the current behavior and the behavior required to reach the desired goal. ________________________ Insert Figure 2 about here. ________________________ 2.5
Design and Procedure
The experiment started immediately after a short familiarization period, during which participants were asked to walk on the treadmill as naturally as possible. The experiment consisted of a pretest, an acquisition phase, and a retention test. The pretest was run on the first day and consisted of one block of 30 trials without concurrent feedback. The acquisition phase consisted of six blocks of 30 trials per day, during a five-day period, resulting in a total of 900 trials. Three groups of participants differed in the frequency of the concurrent feedback that they received during the acquisition phase. The full group received concurrent feedback on every trial. The fading group received concurrent feedback on 100% of the trials in the first two blocks of each session, on 66% of the trials of the middle two blocks of each session, and on 33% of the final two blocks of each session. The control group did not receive concurrent feedback at all. An additional block of 30 trials was performed without concurrent feedback after each daily session
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Concurrent feedback and learning of the acquisition phase. Finally, a 30-trial retention test without concurrent feedback was run three days after the last day of acquisition. 2.6
Data reduction All data were analyzed with regard to performance outcome and movement kinematics.
For performance outcome, the percentage of correct door passings was calculated as a measure of success rate. A door passing was considered to be successful if participants arrived at the doors between 75% (i.e., 112.5 cm) of maximal aperture during the opening phase and 87.5% (i.e., 131.25 cm) of maximal aperture during the closing phase. These parameters guaranteed a comfortable aperture for correct passing for all participants (for a more extensive explanation see Montagne et al., 2003). With regard to the movement kinematics we first computed the variability of walking speed. The within-subjects standard deviations of the speed profiles were computed for the last six successive 0.5 s time-to-passing intervals before door passing. The rationale for using this variable is related to the observation that visually driven regulations of displacements make behavior more variable in the vicinity of the “target” (e.g., Lee, Lishman, & Thomson, 1982). This variable has been used to locate visual regulations of the displacement. However, it does not account for the functionality of these regulations. A second aspect of the movement kinematics that we considered is the variability of the current error. The current error is defined as the error that would be observed at the door passing if the current walking speed would not change. Hence, if the speed changes, the current error changes as a result. The current error was computed for each 5 ms interval of each trial and was used to examine how participants regulate their approach. A convergence of the current error towards zero indicates that the changes in walking speed were adaptive. The implementation of
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Concurrent feedback and learning this procedure resulted in a distinct current error profile for each individual approach. Note that the current error is equal to the concurrent feedback. The time course of the variability of the current error is said to reflect the regulation behavior of participants (Montagne et al., 2003). An increase in the variability in walking speed together with a decrease in the variability of the current error indicates adaptive changes in walking speed. 3
Results 3.1
Pretest
We conducted a one-way analysis of variance (ANOVA) with success rate in the pretest as dependent variable. As expected, the pretest performance of the groups did not differ significantly (F(2,15) = 0.3748, p >.05; see also Figure 3). 3.2
Acquisition
We performed a 3 Group (control, full, and fading) x 5 Day (Days 1 to 5) two-way analysis of variance (ANOVA) with repeated measures on the last factor and with success rate as dependent measure. This analysis concerned the additional daily blocks of 30 trials without concurrent feedback. The main effect of Day was significant (F(4,36) = 29.65, p .05). The Group x Day interaction did not reach significance (F(8,60) = 1.90, p
