Detection of biological and nonbiological motion.

Often it is claimed that humans are particularly sensitive to biological motion. Here, sensitivity as a detection advantage for biological over nonbiological motion is examined. Previous studies comparing biological motion to nonbiological motion have not used appropriate masks or have not taken into account the underlying form present in biological motion. The studies reported here compare the detection of biological motion to nonbiological motion with and without form. Target animation sequences represented a walking human, an unstructured translation and rotation, and a structured translation and rotation. Both the number of mask dots and the size of the target varied across trials. The results show that biological motion is easier to detect than unstructured nonbiological motion but is not easier to detect than structured nonbiological motion. The results cannot be explained by learning over the course of data collection. Additional analyses show that mask density explains masking of different size target areas and is not specific to detection tasks. These data show that humans are not better at detecting biological motion compared to nonbiological motion in a mask. Any differences in detection performance between biological motion and nonbiological motion may be in part because biological motion always contains an underlying form.