Grasping a fruit: selection for action

Abstract

This study used a natural task, with no emphasis placed on speeded responses, to investigate unconscious information processing. Using the ELITE system, a kinematic analysis was performed of the upper limb reach-to-grasp movement. Nine experiments explored how the presence of distractors affects the transport and grasp component of this movement. Experiment 1 showed that the kinematics for grasping apples, mandarins, cherries, and bananas were measurably different. Experiments 2A-D, 3, and 4 showed that these kinematics were not affected by the presence of nearby distractor fruits of either the same or a different kind. In Experiment 5, interference effects became evident when participants were required to perform a subsidiary task involving the distractor (counting the number of times a laterally placed fruit was illuminated). Experiment 6, requiring both grasping a target fruit and counting the number of times that this fruit was illuminated, revealed no interference effects. Taken together, these results suggest that selection for action does not involve substantial passive processing of distractors. However, dual-action processing of simultaneously presented objects does appear to involve automatic processing of even the task-irrelevant properties of the distractor.