Does the brain encode the gaze of others as beams emitted by their eyes?

Gaze and Arrows: Does the Gaze-Following Patch in the Posterior Temporal Cortex Differentiate Social and Symbolic Spatial Cues?

The gaze-following patch (GFP) is located in the posterior temporal cortex and has been described as a cortical module dedicated to processing other people's gaze-direction in a domain-specific manner. Thus, it appears to be the neural correlate of Baron-Cohen's eye direction detector (EDD) which is one of the core modules in his mindreading system-a neurocognitive model for the theory of mind concept. Inspired by Jerry Fodor's ideas on the modularity of the mind, Baron-Cohen proposed that, among other things, the individual modules are domain specific. In the case of the EDD, this means that it exclusively processes eye-like stimuli to extract gaze-direction and that other stimuli, which may carry directional information as well, are processed elsewhere. If the GFP is indeed EDD's neural correlate, it must meet this expectation. To test this, we compared the GFP's BOLD activity during gaze-direction following with the activity during arrow-direction following in the present human fMRI study. Contrary to the expectation based on the assumption of domain specificity, we did not find a differentiation between gaze- and arrow-direction following. In fact, we were not able to reproduce the GFP as presented in the previous studies. A possible explanation is that in the present study-unlike the previous work-the gaze stimuli did not contain an obvious change of direction that represented a visual motion. Hence, the critical stimulus component responsible for the identification of the GFP in the previous experiments might have been visual motion.

Visual motion assists in social cognition

Recent evidence suggests that our brains may generate subtle, fictitious motion signals streaming from other people to the objects of their attention. However, the functional significance of this internally-generated motion signal remains unclear. Here, we tested whether subthreshold motion processing plays a causal role in judging others’ attention. Participants viewed a display including faces, objects, and a subthreshold motion hidden in the background. Judgments of the attentional state of the faces were significantly altered by the motion signal. Control experiments indicated the effect was specific to judging attention. These findings suggest that a crucial aspect of social cognition, monitoring others’ attention, draws on useful but highly physically inaccurate models of social agents in the world, rooted in low-level perceptual mechanisms.

Recent evidence suggests a link between visual motion processing and social cognition. When person A watches person B, the brain of A apparently generates a fictitious, subthreshold motion signal streaming from B to the object of B’s attention. These previous studies, being correlative, were unable to establish any functional role for the false motion signals. Here, we directly tested whether subthreshold motion processing plays a role in judging the attention of others. We asked, if we contaminate people’s visual input with a subthreshold motion signal streaming from an agent to an object, can we manipulate people’s judgments about that agent’s attention? Participants viewed a display including faces, objects, and a subthreshold motion hidden in the background. Participants’ judgments of the attentional state of the faces was significantly altered by the hidden motion signal. Faces from which subthreshold motion was streaming toward an object were judged as paying more attention to the object. Control experiments showed the effect was specific to the agent-to-object motion direction and to judging attention, not action or spatial orientation. These results suggest that when the brain models other minds, it uses a subthreshold motion signal, streaming from an individual to an object, to help represent attentional state. This type of social-cognitive model, tapping perceptual mechanisms that evolved to process physical events in the real world, may help to explain the extraordinary cultural persistence of beliefs in mind processes having physical manifestation. These findings, therefore, may have larger implications for human psychology and cultural belief.