[Effect of luminance on perception of gaze direction in Japanese].

When the luminance of one side of the sclera is darkened artificially, the perceived direction of gaze biases toward the darker side of the sclera. This gaze effect was measured in photographic and schematic images of eyes using Japanese subjects. The effect was larger than previous results: the gaze shift induced by luminance reached 40 deg of gaze or more. The luminance of the iris also affected the results. The effect of scleral darkening was compared to the gaze shift induced by an actual shift of the iris. The results suggest that one mechanism for gaze judgment is based on low-level analysis of the luminance configuration within the eye. This effect might appear to be large in Japanese subject because of their equally dark iris.