Abstract
Tools are manipulable objects that, unlike other objects in the world (e.g., buildings), afford specific action procedures closely linked to object identity. Several studies have shown that differences between structural (e.g., spoon handle size, shape and orientation) and learned functional (e.g., stir, poor or feed) properties of tools can translate to distinct motor affordances. Most studies to date however have used pictures instead of real tools and measured reaction times rather than hand movement kinematics. To investigate how tool identity and subsequent use affect grasping kinematics 18 participants performed two grasping tasks with their right-hand: 1) grasp-to-use (GTU), where participants grasped a tool to demonstrate its typical use; and 2) grasp-to-move (GTM) where participants grasped a tool to move it from one location to another. Critically, participants grasped real 3D familiar kitchen tools with the same handle, so that any kinematic effects could not be simply due to the structural differences between tool handles. Moreover, to control for differences between GTU and GTM kinematics we only analysed the first portion of the movement (i.e., grasping the handle), as this was identical between tasks and tools. We found that participants presented larger grip apertures for the GTU than the GTM tasks, which may reflect differences in the kinematics of subsequent actions following the handle grasp. Moreover, for both tasks participants presented larger grip apertures for tools that had larger tool heads (e.g., whisk) compared to tools with smaller tool heads (e.g., knife), even though the tool handle that was grasped was of identical size across tools. These results indicate that tool identity plays a critical role in action planning and execution.
Meeting abstract presented at VSS 2018