Answer:
Preferential looking technique.
Step-by-step explanation:
According to the American Psychological Association, the preferential looking technique is "an experimental method for assessing the perceptual capabilities of nonverbal individuals (e.g., human infants, nonhuman animals)". If the average infant looks longer at the second stimulus, this suggests that the infant can discriminate between the stimuli. This method has been used extensively in cognitive science and developmental psychology to assess the character of infant's perceptual systems, and, by extension, innate cognitive faculties. An investigator or examinor observes the infants behavior to determine which stimulus the infant fixates on.