Grasping possibilities for action: influence of object function and action capabilities.

The purpose of this study was to investigate the influence of object function and the observer's action capabilities on grasp facilitation. We used a stimulus-response compatibility (SRC) protocol in which participants were asked to reach and grasp a drinking glass using one of two grasps - the thumb-up or the thumb-down grasp. The reaction time (RT) was used as the index of grasp facilitation. In Experiment 1, we found evidence for the facilitation of "functionally relevant" grasps - where the type of grasp facilitated depended on the location of opening but not the shape of the object. However, this effect was found only when attention was directed toward the location of the opening. In Experiments 2 and 3, we found that this facilitation was also affected by whether participants had the ability to functionally interact with the object. These results show that S-R compatibilities are influenced both by the object's function and the actor's action capabilities, and are interpreted in Gibson's (1979) framework of affordances.