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Angela M. Brown, Delwin T. Lindsey, Jaime A. Miracle, PremNandhini Satgunam; D-max for stereopsis in human infants. Journal of Vision 2005;5(8):770. doi: 10.1167/5.8.770.
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Infants can perceive 3D shape from horizontal binocular stereo cues only after age 2–4 months. Is this late emergence because of an overall immaturity of the spatial aspects of early visual processing? If infant receptive fields are uniformly extra-large (under a phase-based model), or if infant vision compares visual information over large distances within the visual field (under a position-based model), d-max is predicted to be larger for infants than for adults.
We studied the stereoptic detection of large values of binocular disparity by infants aged 12–20 wks, using forced-choice preferential looking. We measured detection of a 3-D target portrayed by horizontal binocular disparity (crossed or uncrossed, 0.2 deg–3 deg) within a random texture, compared to a “catch trial” stimulus portrayed by an equal value of vertical binocular disparity. We used 2AFC to collect control data on adults. 12-wk-olds showed no evidence of binocular stereopsis at any disparity value. Stereopsis emerged as infant performance improved over the range 0.5 deg–1 deg, and infants over age 13 wks generally had stereopsis. Infant and adult performance was remarkably similar for binocular disparities of 1deg, 2 deg and 3 deg. Neither infants nor adults correctly detected a horizontal binocular disparity of 3 deg.
The d-max for stereopsis is 2 deg–3 deg, and is about the same for infants and adults, starting as soon as binocular stereopsis can be measured. Under a phase-based model of stereopsis, we find no evidence of uniformly larger receptive fields serving as the basis of binocular stereopsis in infants. Under a position-based model, we find no evidence that infants compare binocular information over larger distances than adults. Our experiment provides no evidence of any immaturity in the purely spatial aspects of early visual processing in infants. Some other immaturity, for instance insensitivity to contrast, especially at high spatial frequencies, must explain their poor stereopsis.
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