Abstract
Heider and Simmel (1944) have shown that the motion of geometric shapes can be perceived as animate and goal-directed behavior. Neuroimaging studies have shown that viewing such displays evokes strong activation in temporoparietal cortex, including areas in and near the posterior superior temporal sulcus (pSTS). These brain regions are sensitive to socially relevant information, and have been implicated in the perception of biological motion and in ‘theory of mind’ processing. Further investigation of the function(s) of pSTS, however, have been limited by the complex constructions of previous animate displays that make it difficult to determine which low level visual cues trigger the perception of animacy. Also, these displays elicit uncontrolled shifts of attention, making it hard to distinguish the cues influencing perceived animacy from spatial attentional shifting. In the current fMRI study, both of these issues were addressed. Subjects viewed a display containing four moving darts (or arrowheads). Subjects were required to track all four darts continuously and to covertly count how many dot probes briefly flashed upon them. On different trials, the perceived animacy of the darts was manipulated by varying whether the darts moved along their long axis (facing ahead) or orthogonal to their long axis (sideways). We also manipulated whether one dart (the ‘wolf’) chased another dart (the ‘sheep’). Prior behavior results have shown that both the ‘facing ahead’ and ‘chasing’ cues trigger the perception of animacy; however, here both of these animacy manipulations were irrelevant to the dot-probe detection task. Behavioral results revealed no difference in probe detection between conditions, indicating that attention was well controlled. Activation of the pSTS was greater for animate than inanimate displays - suggesting that animacy detection was automatically triggered by these low level cues.
Supported by R01-MH05286.