The Impact of Object Motion on Perceptual Categorization

This study examined the extent to which individuals integrated relevant motion dimensions and disregarded the irrelevant ones. In particular, we were interested in whether individuals would process the motion dimensions independently or would tend to integrate them. Also, we were interested in examining whether some types of dimensions may be more salient than others (for example, the external motion path was compared to the internal deformation of an object or its changing speed). Experiment 1 equated the three motion features with respect to discriminability. Experiment 2 compared the relative contribution of two equated features in both clear and obscured viewing conditions with instructions either present or absent. Experiment 3 examined the phenomenon of attentional shift, in which participants needed to attend to one motion dimension in the first stage of the task and to attend to the second motion dimension (while disregarding the first) in the second stage. The relative control depended on a combination of dimensions, but overall, the motion curve was the most difficult dimension to discriminate. Instructions, but not the viewing conditions, affected the relative control. All three dimensions were treated as integral.