Rotation of Mental Images in Baboons When the Visual Input Is Directed to the Left Cerebral Hemisphere

The mental rotation phenomenon was examined in baboons and humans using a video-formatted mutching-to-sample task. Sample stimuli were presented either centrally or in the right or left visual half-field. Immediately afterward, subjects had to distinguish the previously presented sample stimulus from its mirror image after both had been rotated to the same angular deviation. A mental rotation phenomenon was found in baboons and humans, but in baboons this effect was limited to conditions in which visual input was directed to the right visual half-field. These data represent the first evidence of mental rotation in a nonhuman species.