The eyes have it!: An fMRI investigation

For the past several years it has been thought that cues, such as eye direction, can trigger reflexive shifts in attention because of their biological relevance and their specialized neural architecture. However, very recently, Ristic, Friesen, and Kingstone (2002) reported that other stimuli, such as arrows, trigger reflexive shifts in attention in a manner that is behaviourally identical to those triggered by eyes. Nevertheless these authors speculated that reflexive orienting to gaze direction may be subserved by a neural system—the superior temporal sulcus (STS)—that is specialized for processing eyes. The present study presents fMRI data that provide direct and compelling empirical support to this proposal. Subjects were presented with fixation stimuli that, based on instruction, could be perceived as eyes or as another type of directional cue. Both produced equivalent shifts in reflexive attention, replicating Ristic et al. However, the neural systems subserving the two forms of orienting were not equivalent—with the STS being engaged exceptionally when the fixation stimulus was perceived as eyes.