Abstract
Previous studies have reported reflexive attention shifts using a symbolic cue of a schematic face with eyes moving to the left or right. It is thought that these gaze cues elicit reflexive orienting because the eyes play an important role in social cognition. However, there remains conflicting evidence regarding the type of orienting produced by gaze cues. Here, we sought to clarify the role of gaze cues in attentional orienting by testing the extent to which the gaze cue effect depends on biologically natural gazes. Subjects were presented with a line-drawing of a natural or unnatural face looking left, right, or straight ahead. In the 2-eye condition both eyes looked in the same direction. In the 1-eye condition only one eye looked left or right and the other eye looked straight ahead. In the Cyclops condition the face had only one looking eye. Then a target (an F or T) appeared on either side of the face. The cue-target onset asynchrony (CTOA) was randomized (105ms, 300ms, 600ms, or 1005ms). All cues were uninformative and subjects were told the direction of gaze did not predict target location. Subjects made speeded button press responses to identify the letter. Results show that reaction times (RTs) in the 2-eye condition were faster for valid cues at the 300ms and 600ms CTOAs, indicating that biologically natural gaze cues can elicit reflexive attentional orienting. RTs in the 1-eye condition and the Cyclops condition were only faster for valid cues at the 1005ms CTOA, suggesting that biologically unnatural gaze cues involve goal-driven attentional orienting. Overall RTs were slowest in the Cyclops condition and fastest in the 2-eye condition. Our findings further clarify the role gaze cues play in attention and suggest a specialized brain mechanism for attentional orienting in response to biologically natural gaze shifts.