Abstract

Absolute and increment thresholds were measured for 2-month-old human infants by using long-wavelength adapting fields and short-wavelength test flashes. The test flashes were 500 or 10 msec in duration and varied from 6° to 16° in diameter. The psychometric functions measured in the dark were steep for large, long-duration test flashes and shallow for small, brief flashes. Under conditions of light adaptation, the psychometric functions were consistently steep. The shape of the area–threshold function depended on the criterial percent correct responses; when a criterion of 75% correct responses was used, the slope of the area-threshold function was much steeper than predicted by Ricco’s law. These results are interpreted in the context of a model in which rod-initiated signals saturate at a locus proximal to the rods themselves but distal to most of the considerable spatial pooling of visual signals that occurs in infants.

© 1988 Optical Society of America

Spectral sensitivity and chromatic discriminations in 3- and 7-week-old human infants

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