The Ames window illusion: perception of illusory motion by human infants.

The sensitivity of human infants, 5 1/2-9 months of age, to the illusory oscillation of the Ames window was assessed in three experiments that employed some variant of the habituation-dishabituation and forced-choice preferential looking paradigms. In Experiment 1, three groups--5 1/2, 7 1/2, and 9 months of age--were given a visual choice between rotating rectangular and Ames windows after exposure to a rotating circular form. The two older groups preferred the Ames window. The results of Experiment 2 showed that this preference is not based on structural differences between the two windows. In Experiment 3, familiarization with an Ames window produced a preference for rotary motion while familiarization with a rectangular window produced a preference for oscillatory motion. These results suggest that sensitivity to the illusion emerges around 7 1/2 months of age, an outcome consistent with the emergence, at this time, of sensitivity to pictorial cues to depth.