INFANT VISUAL-ACUITY IS UNDERESTIMATED BECAUSE NEAR THRESHOLD GRATINGS ARE NOT PREFERENTIALLY FIXATED

Grating acuity thresholds obtained by the looking preference procedure have been based on the assumption that infants always prefer to look at visible patterns over blank fields. Consequently, it has been assumed that the infant's preference for gratings, when compared to blank fields, would decline monotonically from 100 to 50% as the gratings increased in spatial frequency from above-threshold gratings to below-threshold gratings. Contrary to that assumption, we now find that the preference function falls significantly below 50% only to rise again at higher spatial frequencies. If preference for the grating drops significantly below 50% then the infant must be preferentially fixating the blank field which, in turn, implies discrimination of the grating. Consequently, grating acuity must exceed that based only on preferences for the grating greater than 50%. © 1979.