Moving and memorizing: Motor planning modulates the recency effect in serial and free recall

Motor planning has generally been studied in situations where participants carry out physical actions without a particular purpose. Yet in everyday life physical actions are usually carried out for higher-order goals. We asked whether two previously discovered motor planning phenomena - the end-state comfort effect and motor hysteresis - would hold up if the actions were carried out in the service of higher-order goals. The higher-order goal we chose to study was memorization. By focusing on memorization, we asked not only how and whether motor planning is affected by the need to memorize, but also how memory performance might depend on the cognitive demands of motor planning. We asked university-student participants to retrieve cups from a column of drawers and memorize as many letters as possible from the inside of the cups. The drawers were opened either in a random order (Experiment 1) or in a regular order (Experiments 2 and 3). The end-state comfort effect and motor hysteresis were replicated in these conditions, indicating that the effects hold up when physical actions are carried out for the sake of a higher-order goal. Surprisingly, one of the most reliable effects in memory research was eliminated, namely, the tendency of recent items to be recalled better than earlier items - the recency effect. This outcome was not an artifact of memory being uniformly poor, because the tendency of initial items to be recalled better than later items - the primacy effect - was obtained. Elimination of the recency effect was not due to the requirement that participants recall items in their correct order, for the recency effect was also eliminated when the items could be recalled in any order (Experiment 3). These and other aspects of the results support recent claims for tighter links between perceptual-motor control and intellectual (symbolic) processing than have been assumed in the past.     

Whole-body posture planning in anticipation of a manual prehension task: Prospective and retrospective effects

This study examined the extent to which the anticipation of a manual action task influences whole-body postural planning and orientation. Our participants walked up to a drawer, opened the drawer, then grasped and moved an object in the drawer to another location in the same drawer. The starting placement of the object within the drawer and the final placement of the object in the drawer were varied across trials in either a blocked design (i.e., in trials where the same start and end location were repeated consecutively) or in a mixed fashion. Of primary interest was the posture adopted at the moment of grasping the drawer handle before pulling it out prior to the object manipulation task. Of secondary interest was whether there were sequential effects such that postures adopted in preceding trials influenced postures in subsequent trials. The results indicated that the spatial properties of the forthcoming object manipulation influenced both the postures adopted by the participants and the degree to which the drawer was opened, suggesting a prospective effect. In addition, the adopted postures were more consistent in blocked trials than in mixed trials, suggesting an additional retrospective effect. Overall, our findings suggest that motor planning occurs at the level of the whole body, and reflects both prospective and retrospective influences.     

Interaction between previous beliefs and cue predictive value in covariation-based causal induction

The main aim of this work was to show the impact of preexisting causal beliefs on causal induction from cause-effect co-occurrence information, when several cues compete with each other for predicting the same effect. Two different causal scenarios -- one social (a), the other medical (b) -- were used to check the generality of the effects. In Experiments 1a and 1b, participants were provided information on the co-occurrence of a two-cause compound and an effect, but not about the potential relationship between each cause by its own and the effect. As expected, prior beliefs -- induced by means of instructions -- strongly modulated the causal strength assigned to each element of the compound. In Experiments 2a and 2b, covariation evidence was provided, not only about the predictive value of the two-cause compound, but also about one of the elements of the compound. When this evidence was available, prior beliefs had less impact on judgments, and these were mostly guided by the relative predictive value of the cue. These results demonstrate the involvement of inferential integrative mechanisms in the generation of causal knowledge and show that single covariation detection mechanisms -- either rule-based or associative -- are insufficient to account for human causal judgment. At the same time, the fact that the power of new covariational evidence to change prior beliefs depended on the availability of information on the relative (conditional) predictive value of the target candidate cause suggests that causal knowledge derived from information on causal mechanisms and from covariation probably share a common representational basis.