We test if infants notice a difference between a blue block and a blue polka-dotted block by measuring the time an infant looks at each when the blocks are next to each other. This is called the technique.

Preferential looking technique.

Explanation:

Preferential looking technique is a method of assessing the visual abilities of people that cannot talk, like a baby.(toddler)

It is an experimental method for assessing the perceptual capabilities of nonverbal individuals(individuals that cannot communicate verbally) Preferential looking tests can be carried out on human infants, nonhuman animals.

Preferential looking technique.

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.