HOW MANIPULABILITY (GRASPABILITY AND FUNCTIONAL USAGE) INFLUENCES OBJECT IDENTIFICATION
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In our environment we do two things with objects: identify them, and act on them. Perhaps not coincidentally, research has shown that the brain appears to have two distinct visual streams, one that is engaged during the identification of objects, and one that is associated with action. Although these visual streams are distinct, there has been increasing interest in how the action and identification systems interact during grasping and identification tasks. In particular, the current research explored the role that previous motor experience with familiar manipulable objects might have on the time it takes healthy participants to identify these objects (relative to non-manipulable objects). Furthermore, previous research has shown that there are multiple, computationally and neuro-anatomically different, action systems. The current research was particularly interested in the action systems involved in 1) grasping, and 2) functionally using an object. Work began by developed a new stimulus set of black & white photographs of manipulable and non-manipulable objects, and collecting ‘graspability’ and ‘functional usage’ ratings (chapter 2). This stimulus set was then used to show that high manipulability was related to faster naming but slower categorization (chapter 3). In chapter 4, the nature of these effects was explored by extending a computational model by Yoon, Heinke and Humphreys (2002). Results from chapter 5 indicated independent roles of graspability and functional usage during tasks that required identification of objects presented either with or without a concurrent mask. Specifically, graspaility effects were larger for items that were not masked; and functional use effects were larger for items that were masked. Finally, chapter 6 indicated that action effects during identification tasks are partly based on how realistic the depictions of the objects are. That is, results from chapter 6 indicated the manipulability effects are larger for photographs than they are for line-drawings of the same objects. These results have direct implications for the design of future identification tasks, but, more broadly, they speak to the interactive nature of the human mind: Action representations can be invoked and measured during simple identification tasks, even where acting on the object is not required.