Developmental changes in infants’ visual response to temporal frequency

To investigate the development of visual responsiveness to variations in temporal frequency three studies were carried out at 4 and at 6 months of age. In the first two studies infants viewed pairs of identical check patterns flashing at 2, 4, and 8 Hz, and their visual preferences were observed. In the first study, where rate covaried with duty cycle (i.e., overall intensity), both age groups exhibited differential fixation as a function of frequency. To find out whether intensity variations were responsible for these results, in the second study intensity variations were eliminated (by equating duty cycle at 50%), and only frequency was varied. This manipulation resulted in the elimination of the previously observed differential response in the 4-month-olds but had no effect on the 6-month-olds ' differential response. As a final check on the role of intensity, in the third study overall intensity was varied while temporal frequency was kept constant. Results showed that 4-month-old infants continued to respond differentially whereas 6-month-olds did not. In sum, these data show that at 4 months of age infants attend to the overall intensity of stimulation and ignore its temporal characteristics, whereas at 6 months of age they no longer atten