Developmentally distinct gaze processing systems: Luminance versus geometric cues

Two experiments examined how the different cues to gaze direction contribute to children's abilities to follow and make explicit judgements about gaze. In each study participants were shown blurred images of faces containing only luminance cues to gaze direction, line-drawn images containing only fine-grained detail supporting a geometric analysis of gaze direction, and unmanipulated images. In Experiment 1a, 2- and 3-year olds showed gaze-cued orienting of attention in response to unmanipulated and blurred faces, but not line-drawn faces. Adult participants showed cueing effects to line drawn faces as well as the other two types of face cue in Experiment 1b. In Experiment 2, 2-year-olds were poor at judging towards which of four objects blurred and line-drawn faces were gazing, whereas 3- and 4-year-olds performed above chance with these faces. All age groups performed above chance with unmanipulated images. These findings are consistent with an early-developing luminance-based mechanism, which supports gaze following, but which cannot initially support explicit judgements, and a later-developing mechanism, additionally using geometric cues in the eye, which supports explicit judgements about gaze.