Grasping an object comfortably: orientation information is held in memory

Abstract

It has been shown that memorized information can influence real-time visuomotor control. For instance, a previously seen object (prime) influences grasping movements toward a target object. In this study, we examined how general the priming effect is: does it depend on the orientation of the target object and the similarity between the prime and the target? To do so, we examined whether priming effects occured for different orientations of the prime and the target objects and for primes that were either identical to the target object or only half of the target object. We found that for orientations of the target object that did not require an awkward grasp, the orientation of the prime could influence the initiation time and the final grip orientation. The priming effects on initiation time were only found when the whole target object was presented as prime, but not when only half of the target object was presented. The results suggest that a memory effect on real-time control is constrained by end-state comfort and by the relevance of the prime for the grasping movement, which might mean that the interactions between the ventral and dorsal pathways are task specific.

Fig. 1

a Experimenter’s view of the setup. Two identical objects were placed on the sliding board, but their orientation could differ. The starting position is indicated by the small black disk. The participant could not see the object that was behind the side occluder. b Schematic drawing of the tools used in experiment 1 and 2. Note that participants interacted with real three-dimensional objects. c The orientations used in experiment 1. Note the different definitions of orientation of the target (α) and grip (β). In this way, an orthogonal grip corresponds to the same value for α and β

Fig. 2

Experiment 1. a Mean initiation time for the two congruency conditions (Cong: congruent; Incong: incongruent); b Mean final grip orientation for the two congruency conditions and for the two target orientations (0° and 50°)

Fig. 3

Experiment 2. a Mean initiation time for the two orientation congruency conditions (Cong: congruent; Incong: incongruent); b mean final grip orientation for the two orientation congruency conditions and for the two target orientations (20° and 70°)

Fig. 4

Schematic drawing of the object parts used in experiment 3. All three parts (blade, handle, whole object) were used as primes, but only the whole object was presented as a target

Fig. 5

Experiment 3. Mean initiation time for the three priming conditions (blade, handle and whole object) as a function of congruency (congruent and incongruent). Error bars correspond to between—participants standard deviations