Exp Brain Res (2007) 179:191–198 DOI 10.1007/s00221-006-0780-4

R E SEARCH ART I CLE

Returning home: location memory versus posture memory in object manipulation Matthias Weigelt · Rajal Cohen · David A. Rosenbaum

Received: 21 June 2006 / Accepted: 25 October 2006 / Published online: 22 November 2006 © Springer-Verlag 2006

Abstract Previous studies of object manipulation have suggested that when participants return an object to the place from which they just carried it, they tend to grasp the object for the target-back-to-home trips close to where they just grasped it for the home-to-target trips [Exp Brain Res 157(4):486–495, 2004; Psychon Bull Rev, 2006]. What was unclear from these previous studies was whether participants recalled postures or locations. According to the posture hypothesis, they remembered what body positions they adopted when they last held the object. According to the location hypothesis, they remembered where they held the object and then took hold of it there or nearby again. To distinguish between these possibilities, we had participants mount or dismount a platform after hometo-target moves and before target-back-to-home moves. In the control condition, they did not change their vertical position relative to the shelf containing the home and target platforms (they merely stepped sideways). We found that participants grasped the

M. Weigelt (&) University of Bielefeld, Bielefeld, Germany e-mail: [email protected] M. Weigelt Max-Planck Institute for Human Cognitive and Brain Sciences, Munich, Germany R. Cohen · D. A. Rosenbaum Department of Psychology, Pennsylvania State University, University Park, PA 16802, USA e-mail: [email protected] D. A. Rosenbaum e-mail: [email protected]

object at nearly the same place along its length as they had before, even if this meant adopting very diVerent postures than before. This outcome is consistent with the location-recall account and is inconsistent with the posture-recall account. The implications for motor planning are discussed.

Introduction Previous research has shown that human participants take hold of objects diVerently depending on what they plan to do with the objects. Such anticipatory eVects were Wrst discovered by Marteniuk et al. (1987), who found diVerences in the speed of the hand as it approached a tennis ball to be tossed or a light bulb to be screwed into a socket. Later, Rosenbaum et al. (1990) showed that university students grasped the same rod with diVerent hand orientations depending on what they were going to do with the rod. When the rod was going to be brought to an orientation that would cause the hand to occupy an awkward Wnal posture (thumb pointing down rather than up), participants generally took hold of the rod in a way that prevented this awkward Wnal posture. Rosenbaum et al. (1990) called the tendency to avoid uncomfortable Wnal postures the end-state comfort eVect. The behaviors that reXected this eVect were observed in subsequent studies (Rosenbaum et al. 1990; Rosenbaum and Jorgensen 1992; Rosenbaum et al. 1995, 1996, 2006; Short and Cauraugh 1997, 1999; Weigelt et al. 2006). The end-state comfort eVect was taken to suggest that actors anticipate future body states. This view is consistent with current conceptions of the importance of goal-state representations in action

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planning (Blakemore et al. 2002; Hommel et al. 2001; Kunde and Weigelt, 2005; Rosenbaum et al. 2001; Wolpert and Flanagan 2001). More recent experiments designed to test the generality of the end-state comfort eVect have shown that university students took hold of a vertically oriented rod at diVerent heights depending on the height to which the rod would be carried (Cohen and Rosenbaum 2004; Rosenbaum et al. 2006). The rod that was used was the wooden shaft of a standard bathroom plunger (i.e., the rod extending up from a rubber base). When the plunger stood at a Wxed initial height and then had to be moved to a high target, participants grasped the plunger low (close to the base), but when the plunger stood at the same initial height and then had to be moved to a low target, participants grasped the plunger high (farther from the base). In general, participants grasped the plunger at a height that was inversely related to the height to which the plunger would be carried. Analyses of the grasp heights at the initial and terminal positions showed that participants behaved much as did participants in the earlier demonstrations of the end-state comfort eVect, modifying how they initially took hold of the plunger to avoid extreme uncomfortable postures (extreme joint angles) at the ends of movements. An unexpected Wnding that emerged in the studies of grasp-height control pertained to returns of the plunger to its home position. After participants brought the plunger to the target position, they lowered their hand and then reached out once again, this time to grasp the plunger and return it to its (Wxed) home position. If participants had obeyed the end-state comfort eVect for the return moves, they would have grasped the plunger at a point along its length that would have ensured a comfortable Wnal position back at the home site. Thus, they would have grasped the plunger at the same point along its length no matter what the target position was. This is not what happened. Instead, participants grasped the plunger close to where they had grasped it before, when they carried the plunger from the home site to the target site. Cohen and Rosenbaum (2004) called this the grasp height recall eVect. What does the grasp height recall eVect signify? Cohen and Rosenbaum (2004) and Rosenbaum et al. (2006), who replicated the eVect, suggested that it signiWed that participants were making use of memory in their formation of action plans. According to this explanation, the Wrst time a participant encounters a task condition, an action plan is computed based on an assessment of the task demands. When a similar condition is encountered within a very short time frame,

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Exp Brain Res (2007) 179:191–198

participants recall key features of what they just did and Wne tune the plan. This explanation is reminiscent of two-stage models of cognitive problem solving, where it has been hypothesized that the solution to a (math) problem is initially computed (e.g., the product of 13 times 13 is arrived at through multiplication) but is later recalled as a previously stored instance (e.g., the participant recalls the proposition “13 times 13 equals 169”); see Logan (1988). How can one determine what speciWc information is recalled when participants exhibit the grasp height recall eVect? The approach taken here is to distinguish between two hypotheses about what that information could be. One possibility is that participants returned to the posture they adopted when they released the plunger. Another possibility is that participants returned to the location along the length of the plunger where the hand was for the just completed home-totarget trip. The Wrst hypothesis says that what was recalled was represented in intrinsic (body-based) coordinates. The second hypothesis says that what was recalled was represented in extrinsic (allocentric) coordinates. Distinguishing between these alternatives was not only important for shedding light on the sources of the grasp height recall eVect; it was also important for shedding light, more generally, on what is recalled in physical action tasks.

Method We tested the alternative hypotheses by creating situations in which recalling locations and recalling postures would result in diVerent behaviors. As shown in Fig. 1, participants reached out to move the plunger from a home position to a target position, then lowered the hand, and then reached out to move the plunger back to the home position again. This simple procedure was the same as the one used in the previous studies of grasp height. What was new here was that between the home-to-target move and the target-back-to-home move, participants stepped to the right, either down from a platform, up onto a platform, or, in the control condition, merely sideways. By having participants step up onto or down from a podium or merely step sideways, we could ask whether, for target-back-to-home moves, participants tried to grasp the plunger close to where they had done so before in extrinsic coordinates (i.e., at a point close to where they had grasped it relative to the base of the plunger) or in intrinsic coordinates (i.e., at a point close to where they had grasped it before relative to their feet). The main prediction, as shown in Fig. 2, was that if locations were recalled in

Exp Brain Res (2007) 179:191–198

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to a malfunction of the video recording system. This study was approved by the local ethics committee and carried out according to the 1964 Declaration of Helsinki. Apparatus and materials

Fig. 1 Three podium arrangements used in the experiment. Left panel Podium (P) on the left; middle panel no podium; right panel podium on the right. The home shelf (HS) is on the left and the target shelves (TS) are on the right in each arrangement. The arrow shows the step participants were asked to take after moving the plunger from the home shelf to any one of the three target shelves. Numbers indicate cylinder height, podium height, and target heights (all in cm)

Fig. 2 Possible strategies for grasping a plunger after holding it while standing on the Xoor (left panel). One strategy is to grasp it on the same shaft location as before (middle panel). Another strategy is to grasp it using the same posture as before to replay the just-performed movement in reverse (right panel). Schematic diagram only, not drawn to scale

the grasp height recall eVect, grasp height for return moves should remain invariant with respect to extrinsic coordinates. By contrast, if postures were recalled in the grasp height recall eVect, then grasp height for return moves should remain invariant with respect to intrinsic coordinates. Participants Fifteen students (9 female and 6 male; mean age = 24.7 years; age range 20–32 years) from the University of Munich participated. All the participants characterized themselves as both right-handed and neurologically healthy, and all were naive to the purpose of the study. Each participant was tested individually. Before testing, each participant provided his or her informed consent. After the experiment was completed, each participant received 5 Euros (the equivalent of approximately 6 US Dollars) for participation. One participant had to be excluded from the study due

The apparatus was similar to the one used by Cohen and Rosenbaum (2004) except for a wooden podium (30 cm wide, 50 cm deep and 10 cm high), which was added to the set-up in particular conditions. When subjects were not standing on the podium, they were asked to stand on one of two rectangular pieces of paper (21.0 cm by 29.6 cm) taped to the Xoor, 30 cm in front of the bookshelf, on the left or on the right. The bookshelf consisted of three shelves at heights of 50, 85, and 120 cm. A wooden target platform rested on each of these shelves on the right, and a home platform extended 15 cm from the middle shelf on the left. On the home platform stood a standard toilet plunger (only used in this and similar experiments) whose wooden shaft was cylinder, 2.5 cm in diameter and 50 cm high, and was supported by a circular rubber base, 10 cm in diameter and 5 cm high. The weight of the cylinder was counterbalanced by a brick positioned on the inner end of the wooden platform (i.e., behind the base from the participant’s perspective). Each of the three target shelves could be pushed into the bookshelf or pulled out of the bookshelf, causing it to extend 15 cm from the edge of the bookshelf, as was the case for the home shelf. The target shelves also had bricks in the back to counterbalance the cylinder and base. Design and procedure Each participant was tested with all three target shelf heights in all three conditions (podium-absent, podium-left and podium-right). The order of podium conditions was randomly assigned to each participant prior to testing. When a particular podium condition was selected, the participant proceeded until all target shelf heights were tested in that podium condition. The target shelf heights were randomly presented within each podium condition. After all target shelf heights were tested for one podium condition, the experimenter changed the set-up to continue with the next block, until all podium conditions were tested. Before the participant started the experiment, she/ he was told that we were recording short video sequences to be shown in a memory experiment with another group of participants. This cover story was necessary because a video camera stood on a tripod to the right of the bookshelf, in full view of the participants.

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We asked the participants to perform the task in a relaxed, natural fashion, but to pay close attention to the instructions of the experimenter, who announced each action sequence to be performed. The camera lens was focused to fully capture the whole length of the cylinder on the home platform. A colored dot was taped to the back of the right hand of each participant. The participants were instructed to keep their left hands by their sides at all times and only to move their right hands when told to do so by the experimenter. They were further instructed to hold the cylinder securely, and to move it at a comfortable, unhurried speed while performing the task. At the beginning of each trial in the podium-absent conditions, the participant was asked to step to the paper on the left, in front of the home shelf. The experimenter then pulled out one of the three target platforms on the right, indicating the next placement position of the cylinder. The participant was instructed to take hold of the cylinder with the right hand and to move it to the target platform, then to set the cylinder with its base down on that shelf, and then to return the hand back to the side of the body. This completed the home-to-target move. Next, the experimenter asked the participant to step over to the right, onto the paper in front of the target shelves. For the following targetback-to-home move, the participant was instructed to grasp the plunger, step back over to the left, onto the paper in front of the home shelf, and return the plunger to the home shelf. This sequence of events was repeated for each target shelf height, constituting one block. When the moves to and from one target were completed, the experimenter pushed back the platform into the bookshelf and consulted a previously prepared design sheet before pulling out the next target shelf, whereupon the next home-to-target move and targetback-to-home move sequence was tested. In the podium-present conditions, the experimenter placed the podium either in front of the home shelf or in front of the target shelves, where it remained until the plunger had been taken by the participant to all target shelf heights twice. Then, the experimenter either moved the podium to the other side of the bookshelf or removed it, depending on which block was next. If the podium was placed in front of the home shelf (podium-left), the participant was asked to step on to the podium and then to move the cylinder to the target platform. After the cylinder was placed on the target platform, the participant took a step down from the podium and stood with his or her feet on the paper in front of the target shelves. She/he then reached for the plunger again and next took hold of it before taking a step back up on to the podium, whereupon she/he

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Exp Brain Res (2007) 179:191–198

placed it back on the home shelf. As in the no-podium condition, this procedure was repeated twice for each trial before the next target shelf height was tested. If the podium was placed in front of the target shelves (podium-right), the participant was asked to stand on the piece of paper in front of the home shelf and take hold of the plunger on the home shelf, next to place the plunger on the target shelf, and then to step up the podium. To return the plunger from the target platform back to the home platform, the participant reached for the plunger again, took a step down from the podium (with the plunger in his or her hands), and stood on the paper in front of the home shelf, before Wnally placing the plunger on the home shelf. As in the other two conditions, this procedure was repeated twice for each target shelf height. Each participant was tall enough to comfortably reach the top of the cylinder when it was placed on the top platform. The entire session lasted for about 20 min. The participants were debriefed after the session. OV-line video analysis Because the performance of each participant was captured on videotape, it was possible to estimate each participant’s grasp heights on the plunger shaft after the testing session. We estimated the position of the right hand on the cylinder at two critical moments in each transport cycle: (1) when the participant took hold of the plunger to carry it to the target platform and (2) when the participant returned the plunger from the target platform and set it down on the home shelf. Because the participants were instructed to Wrmly grasp the plunger and hold it securely during the transport action (i.e., not to let the cylinder slip through their Wngers), we assumed that the grasp heights on the plunger for the target-back-to-home moves were faithfully reXected back at the home shelf at the ends of the target-to-home moves. Measuring the grasp heights at this one position for all movement cycles ensured standardization of measurement. The way we used the videos to measure participants’ grasp heights was as follows. For each measurement, the experimenter froze the picture frame of interest and measured the on-screen distance between the colored dot (which was placed at the back of the right hand of each participant before the experiment) and the bottom of the cylinder base. The experimenter also measured the on-screen length of the cylinder for each measurement sample. This was done as an extra precaution in case the participants slightly varied the position of the plunger on the home shelf, thus changing

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Results

30 20 10 0

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85 120 Shelf Height (cm) Left Platform

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85 120 Shelf Height (cm)

Extrinsic coordinates The main eVects for shelf height, F(2, 26) = 19.648, P < 0.001, direction, F(1,13) = 7.262, P < 0.05, and platform, F(2, 26) = 4.957, P < 0.05, were signiWcant, whereas the main eVect of repetition was not, F(1,13) = 0.203, P < 0.092. In addition, the direction £ platform interaction, F(2, 26) = 8.357, P < 0.01, was signiWcant, as was the shelf height £ repetition interaction, F(2, 26) = 3.848, P < 0.05, but none of the other interactions reached or approached signiWcance. To further examine the direction £ platform interaction, we collapsed the data over the factors shelf height and repetition and conducted an additional 2 (direction) £ 3 (platform) ANOVA. A graphic depiction of this interaction can be seen in the lower panel of Fig. 4, where the diVerent grasp heights for home-to-target No Platform

50 40 30 20 10 0

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85 120 Shelf Height (cm) No Platform

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85 120 Shelf Height (cm)

Fig. 3 Mean grasp height relative to feet (top panels) and relative to plunger base (bottom panels) when the platform was on the left (left panels), when the platform was on the right (right panels), and when there was no platform (middle panels). The two curves are for the Wrst home to target moves (right-pointing triangles) and for the Wrst target-back-to-home moves (left-pointing trian-

Grasp Height Relative To Plunger Base (cm)

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Grasp Height Relative To Feet (cm)

Left Platform 50

Grasp Height Relative To Plunger Base (cm)

Grasp Height RelativeTo Plunger Base (cm)

Grasp Height Relative To Feet (cm)

As seen in Fig. 3, the grasp heights for the target-backto-home moves were much more similar to the grasp heights for the home-to-target moves when the data were plotted relative to the plunger base (i.e., in extrinsic coordinates) than when the data were plotted relative to the feet (i.e., in intrinsic coordinates). To evaluate these impressions, we analyzed participants’ grasp height in extrinsic and intrinsic coordinates and we submitted the data to two separate repeated-measures analyses of variance whose designs were 3 (shelf height: 50 vs. 85 vs. 120 cm) £ 2 (direc-

tion: HT vs. TH) £ 3 (platform: left vs. none vs. right) £ 2 (repetition: 1st vs. 2nd). One ANOVA used the data relative to the plunger base (extrinsic coordinates). The other used the data relative to the feet (intrinsic coordinates).

Grasp Height Relative To Feet (cm)

the apparent length of the cylinder. To analyze the data, we divided the distance from the bottom of the cylinder base to the colored dot by the distance from the bottom of the cylinder to the top of the cylinder. Then, to express the grasp height in centimeters, we multiplied the actual length of the cylinder by the ratio obtained in the preceding step. That value (in cm) was reported as the grasp height.

Right Platform 50 40 30 20 10 0

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85 120 Shelf Height (cm) Right Platform

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85 120 Shelf Height (cm)

gles). Because the home position was on the left, participants carried out home-to-target moves while standing on the platform in the left platform condition and carried out target-back-to-home moves while standing on the platform in the right platform condition. Error bars show §1 SE

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Exp Brain Res (2007) 179:191–198

grasp height relative to feet (cm)

196 35

HT 30

TH

25 20 15 10 5

grasp height relative to plunger base (cm)

left platform

no platform

right platform

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HT 30

TH

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Fig. 4 Direction £ platform interaction using, in the upper panel, grasp height relative to the feet (intrinsic coordinated) and, in the lower graph, grasp height relative to the plunger base (extrinsic coordinates) when the platform was on the left, when the platform was on the right, and when there was no platform. The two curves are for home to target moves (solid circles) and for targetback-to-home moves (empty circles). Because the home position was on the left, participants carried out home-to-target moves while standing on the platform in the left platform condition and carried out target-back-to-home moves while standing on the platform in the right platform condition. Error bars show §1 SE

moves (HT) and target-back-to-home moves (TH) are displayed for the various platform conditions. Followup t-tests of the signiWcant direction £ platform interaction, F(2, 26) = 8.440, P = 0.001, revealed that mean grasp height was about 2 cm lower for TH moves than for HT moves when the platform was placed to the left (22.31 vs. 24.29 cm, respectively) and when there was no platform (20.16 vs. 22.15 cm, respectively), with the signiWcance of both of these two-tailed tests being high, P < 0.01. This small but signiWcant diVerence was absent when the platform was placed to the right (22.17 vs. 21.54 cm). Intrinsic coordinates The main eVects for shelf height, F(2, 26) = 19.626, P < 0.001, direction, F(1,13) = 7.213, P < 0.05, and platform, F(2,26) = 138.141, P < 0.001, were signiWcant,

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whereas the main eVect for repetition, F(1,13) = .202, P = 0.092, was not. Also, the direction £ platform interaction, F(2,26) = 280.566, P < 0.001, and the shelf height £ repetition interaction, F(2,26) = 3.813, P < 0.05, both reached signiWcance. None of the other interactions reached or approached signiWcance. To further examine the direction £ platform interaction, we collapsed the data over shelf heights and repetitions and conducted an additional 2 (direction) £ 3 (platform) ANOVA. A graphic depiction of this interaction can be seen in the upper panel of Fig. 4, where the diVerent grasp heights for home-totarget moves (HT) and target-back-to-home moves (TH) are displayed for the various platform conditions. Follow up t-tests of the signiWcant direction £ platform interaction, F(2,26) = 281.141, P < 0.001, revealed that the mean grasp height was about 2 cm lower for TH moves than for HT moves when there was no platform (20.16 vs. 22.15 cm, respectively). When the platform was placed to the left, grasp heights were about 8 cm higher for TH moves than for HT moves (32.31 vs. 24.29 cm, respectively). Conversely, when the platform was placed to the right, TH moves were about 9 cm lower than HT moves (12.17 vs. 21.54 cm, respectively).

Discussion Previous studies of object manipulation have suggested that when an object is returned to the place from which it was just carried, participants tend to grasp the object for the target-back-to-home trips close to where they had just grasped it for the home-to-target trips (Cohen and Rosenbaum 2004; Rosenbaum et al. 2006). What was unknown from these previous studies was whether participants recalled postures or locations. According to the posture hypothesis, participants recalled the body positions they adopted when they last held the plunger and adopted that posture again upon taking hold of the plunger for the return trip. According to the location hypothesis, participants recalled the place along the length of the plunger occupied by the hand for the just-completed home-to-target trip. To distinguish between these possibilities, we had participants mount or dismount a platform after some of their home-to-target moves and before some of their target-back-to-home moves. In the control condition, they did not change their vertical position relative to the shelf containing the home and target platforms (they merely stepped sideways). We found that participants grasped the plunger at nearly the same place along the length of the plunger as they had before (the

Exp Brain Res (2007) 179:191–198

same height above the base of the plunger), even if this meant adopting very diVerent postures than before (diVerent heights above the feet). Figure 3 reXects this behavioral strategy. The grasp heights for target-backto-home moves were much more similar to the grasp heights for the home-to-target moves when the data were plotted relative to the plunger base (i.e., in extrinsic coordinates) than when the data were plotted relative to the feet (i.e., in intrinsic coordinates). This outcome shows that participants recalled locations on the plunger, rather than their previously attained goal postures, a Wnding that is consistent with the locationrecall account and inconsistent with the posture-recall account. The present Wndings also help to address an even more basic concern about the interpretation of the previous grasp-height results. That concern was whether participants were in fact relying on memory to select their grasp heights for return moves. One need not assert that if participants grasped the plunger for target-to-home moves close to where they had grasped the plunger for home-to-target moves, they did so because they remembered either the previous grasp location or the previous grasp posture. It might just be a coincidence that the grasp heights were so closely related. The present results argue against this possibility because, as shown in Fig. 3, grasp heights were much better explained by assuming location invariance than posture invariance. If successive grasp heights were related by coincidence only, one would not expect one dimension of control (location) to account so much better for the relation than another dimension of control (posture). What are the broader implications of our Wndings? First, our results agree with the notion that memory for information expressed in extrinsic coordinates is more robust than, or is relied on more, memory for information expressed in intrinsic coordinates (see Smyth 1984, for a review). Interestingly, studies of serial reaction time have led to the same conclusion. In those studies, it has been found that participants pressing buttons associated with lights as quickly as they can are far more disrupted when the mapping of lights to buttons changes than when the mapping of Wngers to buttons changes (Willingham et al. 2000). Second, our results have implications for the role that posture memory may play in motor planning. According to the posture-based motion planning theory (Rosenbaum et al. 1995, 2001), goal postures are speciWed before movements to those goal postures are speciWed. The greater ease of repeating movements (i.e., shorter initiation latencies and decreasing endpoint variability) is explained in the theory by the

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availability of more and better stored goal postures for those movements. Having these goal postures available in memory reduces the time needed for motor planning because, according to the hypothesis, recalling postures provide a quicker basis for specifying goal postures than generating goal postures de novo on the basis of new computations; see Rosenbaum et al. (1995, 2001) for details. The latter proposal is reminiscent of Logan’s distinction between generation and recall of problem solutions, mentioned earlier in this article. Previous work showed that when participants had to reach to a speciWed target location repeatedly with alternating hands, left–right errors were mirrored across hands, as would be expected if postures were copied from one arm to the other (Rosenbaum et al. 1999). The present study demonstrates that in addition to remembering postures, participants can remember locations in extrinsic space when they change position vis-à-vis an object during two consecutive motor actions. The question of why participants rely on location memory in some situations and on posture memory in other situations remains to be answered.

References Blakemore SJ, Wolpert DM, Frith CD (2002) Abnormalities in the awareness of action. Trends Cognit Sci 6:237–242 Cohen RG, Rosenbaum DA (2004) Where grasps are made reveals how grasps are planned: generation and recall of motor plans. Exp Brain Res 157(4):486–495 Hommel B, Muesseler J, Aschersleben G, Prinz W (2001) The theory of event coding (TEC): a framework for perception and action planning. Behav Brain Sci 24(5):849–878 Kunde W, Weigelt M (2005) Goal-congruency in bimanual object manipulation. J Exp Psychol Human Percept Perform 31(1):145–156 Logan GD (1988) Toward an instance theory of automatization. Psychol Rev 95:492–527 Marteniuk RG, MacKenzie CL, Jeannerod M, Athenes S, Dugas C (1987) Constraints on human arm movement trajectories. Can J Psychol 4:365–378 Rosenbaum DA, Jorgensen MJ (1992) Planning macroscopic aspects of manual control. Hum Move Sci 11:61–69 Rosenbaum DA, Marchak F, Barnes HJ, Vaughan J, Slotta JD, Jorgensen MJ (1990) Constraints for action selection: overhand versus underhand grip. In: Jeanerod M (ed) Attention and performance XIII. Lawrence Erlbaum Associates, Hillsdale, pp 321–342 Rosenbaum DA, Loukopoulos LD, Meulenbroek RG, Vaughan J, Engelbrecht SE (1995) Planning reaches by evaluating stored postures. Psychol Rev 102:26–67 Rosenbaum DA, van Heugten CM, Caldwell GE (1996) From cognition to biomechanics and back: the end-state comfort eVect and the middle-is-faster eVect. Acta Psychol 94:59–85 Rosenbaum DA, Meulenbroek RJ, Vaughan J (1999) Remembered positions: stored locations or stored postures? ExpBrain Res 124:503–512

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198 Rosenbaum DA, Meulenbroek RG, Vaughan J, Jansen C (2001) Posture-based motion planning: applications to grasping. Psychol Rev 108:709–734 Rosenbaum DA, Halloran E, Cohen RG (2006) Precision requirements aVect grasp choices. Psychon Bull Rev Short MW, Cauraugh JH (1997) Planning macroscopic aspects of manual control: end-state comfort and point-of-change eVects. Acta Psychol 96:133–147 Short MW, Cauragh JH (1999) Precision hypothesis and the endsate comfort eVect. Acta Psychol 100:243–252

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Exp Brain Res (2007) 179:191–198 Smyth MM (1984) Memory for movements. In: Smyth MM, Wing AM (eds) The psychology of human movement. Academic, London, pp 83–117 Weigelt M, Kunde W, Prinz W (2006) End-state comfort in bimanual object manipulation. Exp Psychol 53(2):143–148 Willingham DB, Wells LA, Farrell JM, Stemwedel ME (2000) Implicit motor sequence learning is represented in response locations. Memory Cognit 28:366–375 Wolpert DM, Flanagan JR (2001) Motor prediction. Curr Biol 11:729–723

Returning home: location memory versus posture ...

studies was whether participants recalled postures or locations. According to the posture hypothesis, they remembered what body positions they adopted when.

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