Dissociating the detection of intentionality from animacy in the right posterior superior temporal sulcus

Abstract

Certain motion patterns can cause even simple geometric shapes to be perceived as animate. Viewing such displays evokes strong activation in temporoparietal cortex, including areas in and near the (predominantly right) posterior superior temporal sulcus (pSTS). These brain regions are sensitive to socially relevant information, but the nature of the social information represented in pSTS is unclear. For example, previousstudies have been unabletoexplore theperceptionofshifting intentions beyondanimacy. Thisisdueinparttothe ubiquitous use of complex displays that combine several types of social information, with little ability to control lower-level visual cues. Hereweaddress thischallengebymanipulating intentionality with parametric precisionwhileholdingcuestoanimacy constant.Human subjects were exposed to a "wavering wolf" display, in which one item (the wolf) chased continuously, but its goal (i.e., the sheep) frequently switchedamong othershapes.Bycontrasting thiswith three othercontrol displays,wefind that the wolf'schangingintentions gave rise to strong selective activation in the right pSTS, compared with (1) a wolf that chases with a single unchanging intention, (2) very similar patterns of motion (and motion change) that are not perceived as goal-directed, and (3) abrupt onsets and offsets of moving objects. These results demonstrate in an especially well controlled manner that right pSTS is involved in social perception beyond physical properties such as motion energy and salience. More importantly, these results demonstrate for the first time that this region represents perceived intentions beyond animacy. © 2012 the authors.