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R Held

Publications and source records attributed to R Held.

29 records · Page 2Linked to original sources
PubMed1975

Orientational anisotropy in infant vision.

Infants prefer to look at horizontal and vertical gratings rather than at oblique gratings only when they are at or near threshold spatial frequencies, as would be expected if acuity for oblique edges is lower than that for horizontal and vertical edges. That such a bias exists as early as 6 weeks of age suggests that the orientational asymmetry of the visual system depends on endogenous maturation rathat than exposure to a carpentered world.

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PubMed1975

Comparison of visually guided reaching in normal and deprived infant monkeys.

A stump-tailed macaque, deprived of sight of its hands and body since shortly after birth, appears to be deficient in the accuracy and precision of its visually guided reaching. These deprived monkeys quickly develop adequate reaches if they are allowed to view their hands. To assess the deficit, we developed a method of open-loop testing (no sight of the reaching limb) for use on both an experimental group deprived of sight of limbs and a control group raised under identical restraints but allowed sight of limbs. The results show that the deprived monkeys can learn to reach a given visible target, but the learned reach is not as precise in the training condition or as precise to new target directions as it is for controls. Furthermore, there is little intermanual transfer of reaching skill for the experimentals but nearly 100% transfer for the controls. Finally, experimentals show a loss of precision in retention testing following a lack of practice, but controls do not. We conclude that the differences in visually guided reaching behavior of the two groups is evidence that the normal accuracy results from unconstrained vision of the hands which produces a mapping of the coordinates of motor response onto the space of vision.

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PubMedDate not supplied

Binocular function in human infants: correlation of stereoptic and fusion-rivalry discriminations.

Studies of stereopsis in infants have shown that the average age of onset is 3.5 months. This is the same age at which infants first show evidence of another binocular function, namely, preference for binocularly fusible patterns over rivalrous ones. We tracked the development, using two-alternative forced-choice preferential looking, of the two forms of binocular function in 17 infants, 11 male and six female. They were tested at regular intervals until they showed preferences for 1) a fusible pattern (vertical stripes presented to each eye) over a rivalrous one (vertical stripes presented to one eye, horizontal stripes to the other), and 2) a line stereogram of 32 min crossed disparity over a comparable stereogram with zero disparity. The correlation between the age of onset of the fusion preference (mean 12.4 weeks) and the age of onset of stereopsis (mean 11.0 weeks) was r = 0.79. Female infants showed a preference for the fusible stimulus at a mean age of 9.9 weeks, significantly earlier than the males at a mean age of 13.8 weeks. Similarly, females also showed evidence of stereopsis at an earlier age (9.1 weeks compared with 12.1 weeks for males).

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