Change detection for real-world objects in perihand space.

Recent evidence has demonstrated that observers experience visual-processing biases in perihand space that may be tied to the hands' relevance for grasping actions. Our previous work suggested that when the hands are positioned to afford a power-grasp action, observers show increased temporal sensitivity that could aid with fast and forceful action, whereas when the hands are instead at the ready to perform a precision-grasp action, observers show enhanced spatial sensitivity that benefits delicate and detail-oriented actions. In the present investigation we seek to extend these previous findings by examining how object affordances may interact with hand positioning to shape visual biases in perihand space. Across three experiments, we examined how long participants took to perform a change detection task on photos of real objects, while we manipulated hand position (near/far from display), grasp posture (power/precision), and change type (orientation/identity). Participants viewed objects that afforded either a power grasp or a precision grasp, or were ungraspable. Although we were unable to uncover evidence of altered vision in perihand space in our first experiment, mirroring previous findings, in Experiments 2 and 3 our participants showed grasp-dependent biases near the hands when detecting changes to target objects that afforded a power grasp. Interestingly, ungraspable target objects were not subject to the same perihand space biases. Taken together, our results suggest that the influence of hand position on change detection performance is mediated not only by the hands' grasp posture, but also by a target object's affordances for grasping.