Brightness discrimination in infancy

Optokinetic nystagmus was elicited in 16 infants, 4 to 69 days of age, by a projected field of moving black and white stripes. The brightness of the field was varied and the minimum intensity eliciting a response was considered the threshold. In the technique used, variations in the intensity of the white stripe also involved variations in the relative intensity of white and black. Therefore, the Weber fraction as well as the difference between white and black stripes was calculated for each threshold. These two measures of threshold response were correlated with age. In both instances the relationship with age was strong and significant, indicating that brightness sensitivity undergoes rapid development in the first two months of life.