Monocular gap stereopsis in infants

In monocular gap stereopsis, one eye perceives a complete rectangular surface while the other eye perceives two small adjacent rectangular surfaces separated by a narrow vertical gap. Our visual system interprets the difference caused by the unmatched monocular images as a depth difference between two small rectangles. In a spontaneous visual preference study, it was asked whether participants aged 4 months responded to the depth effect generated by a monocular gap. Two experimental conditions were conducted. In one (large outer edge disparity condition), the monocular depth effect was twice as strong as in the other one (small outer edge disparity condition), according to the experimental research with adult participants conducted by Pianta and Gillam (2003, Vision Research, Vol. 43, pp. 1937-1950). In both conditions, it was tested whether the stimulus bearing monocular gap stereopsis was preferred over a comparison stimulus without depth. According to the results, the participants preferred looking at the stimulus with monocular stereopsis in the large outer edge disparity condition over doing so in the small outer edge disparity condition. Moreover, the difference between experimental conditions was significant; that is, the infants displayed a stronger spontaneous preference in the condition with the large outer edge disparity than in the condition with the small outer edge disparity. These findings provide evidence to suggest that infants aged 4 months are able to respond to monocular vertical gap information.