People don't keep their heads still when looking to one side, and other people can tell

Citation

Doherty M & Anderson J (2001) People don't keep their heads still when looking to one side, and other people can tell. Perception, 30 (6), pp. 765-767. https://doi.org/10.1068/p2998

Abstract
Twenty pairs of photographs were made of adults looking 25° to the left and 25° to the right while attempting to face forwards. The eye regions of each photograph were concealed. Twenty adults attempted to sort each pair into left-looking and right-looking pictures. They were successful 65% of the time, p less than 0.001. This suggests models have difficulty looking to one side without a perceptible head turn or comparable facial cue. This previously unrecognised phenomenon has implications for research on detection of gaze.

Journal
Perception: Volume 30, Issue 6