Abstract
In daily interactions with the world around us, object sizes critically affect the kinematics and dynamics of goal-directed movements such as pointing or grasping. For instance, ballistic pointing movements are faster the larger their target is (Fitts, 1955). However, because the perceptual and conceptual sizes of objects are mostly consistent in the real world—elephants are almost always perceived and conceptualized as larger than rabbits—it is not clear if we guide movements solely based on our assessment of perceptual size, or if objects' higher-order conceptual sizes also influence action. Here, we compared pointing movements directed at images of real-world objects when their relative perceptual sizes were either congruent or incongruent with their relative conceptual sizes (e.g. an elephant was presented as perceptually larger or smaller than a rabbit, respectively). Participants were instructed to point to the larger or smaller of two simultaneously presented objects in perceptual and conceptual size judgment tasks. We observed that participants pointed to target objects faster when their perceptual and conceptual sizes were congruent compared to incongruent. Furthermore, we demonstrated that when perceptual and conceptual sizes were incongruent, pointing movements were more attracted towards the incorrect object (e.g. in the larger perceptual size judgment task, the conceptually larger but perceptually smaller object), leading to more curved trajectories. These results were observed in both the perceptual and conceptual size judgment tasks, consistent with prior research showing that perceptual size judgments are impaired when object size is inconsistent with object knowledge (Konkle and Oliva, 2012). Despite this interactive modulation of goal-directed pointing by perceptual and conceptual size, we observed greater overall competition (i.e. curvature), in the conceptual size judgment task. Thus, we propose that assessments of perceptual size have greater influence on action than assessments of real-world conceptual size, despite the fact that both are performed automatically.
Meeting abstract presented at VSS 2017