Discrimination of orientation by human infants.

Successive discrimination of suprathreshold gratings of different orientations by two-month-old infants was tested with the use of a type of familiarization-novelty paradigm. Infants showed clear discrimination between horizontally and vertically oriented gratings. Infants failed, however, to discriminate mirror-image obliques from each other and also failed to discriminate nonmirror-image obliques. Considered along with previous demonstrations in children and adults of a greater confusability of oblique grating pairs relative to that of the horizontal and vertical pair, these findings indicate that this differential confusability of orientation is, at least in part, manifest in humans by two months of age.