Disentangling the contributions of grasp and action representations in the recognition of manipulable objects.

There is an increasing evidence that the action properties of manipulable objects can play a role in object recognition, as objects with similar action properties can facilitate each other's recognition [Helbig et al. Exp Brain Res 174:221-228, 2006]. However, it is unclear whether this modulation is driven by the actions involved in using the object or the grasps afforded by the objects, because these factors have been confounded in previous studies. Here, we attempted to disentangle the relative contributions of the action and grasp properties by using a priming paradigm in which action and grasp similarity between two objects were varied orthogonally. We found that target tools with similar grasp properties to the prime tool were named more accurately than those with dissimilar grasps. However, naming accuracy was not affected by the similarity of action properties between the prime and target tools. This suggests that knowledge about how an object is used is not automatically accessed when identifying a manipulable object. What are automatically accessed are the transformations necessary to interact directly with the object--i.e., the manner in which one grasps the object.