Abstract
Processing visuospatial information is critical for interacting with the world. Though visually-guided actions seem effortless, evidence suggests that they require computations that are complex and distinct from representations underlying perceptual judgments that do not require object-directed action (e.g., Bridgeman, Kirch, & Sperling, 1981; Milner & Goodale, 1995). One such distinction lies in the role of memory: when a visual stimulus is removed and then a movement is initiated, the way in which the action is carried out changes relative to when the stimulus remains visible. It has been proposed these differences exist because action representations are used only for online purposes and disappear or degrade under delay. In the current study we explored how visual-manual action representations develop, and in particular how they interact with memory. Four and six year-old children and adults were presented with wooden blocks of various heights (3–6 cm). Participants were asked to reach and grasp the wooden blocks when they were visible or after the blocks were covered for up to 3 seconds. When the target remained visible during reach/grasp, the children's performance was qualitatively similar to that of adult participants: children scaled their grasp to the size of the target. When the target had to be remembered, the four year olds no longer scaled their grasp to the size of the block, unlike the adult participants. However, in a comparable perceptual judgment task where the participant did not act on the object, children were able to scale their response to the size of the target, even under delay, suggesting children's difficulty in the reaching task was not a general limitation of memory or attention. The unique difficulty for children in representing size-for-action suggests that representations of action are distinct from representations for perceptual judgment tasks and that these representations undergo different developmental timelines.