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few times they experience them and become less interested in them with more frequent exposure. Developmental
psychologists have used this general principle to help them understand what babies remember and understand.
In the habituation procedure, a baby is placed in a high chair and presented with visual stimuli while a video camera
records the infant’s eye and face movements. When the experiment begins, a stimulus (e.g., the face of an adult)
appears in the baby’s field of view, and the amount of time the baby looks at the face is recorded by the camera. Then
the stimulus is removed for a few seconds before it appears again and the gaze is again measured. Over time, the baby
starts to habituate to the face, such that each presentation elicits less gazing at the stimulus. Then, a new stimulus
(e.g., the face of a different adult or the same face looking in a different direction) is presented, and the researchers
observe whether the gaze time significantly increases. You can see that, if the infant’s gaze time increases when a new
stimulus is presented, this indicates that the baby can differentiate the two stimuli.
Although this procedure is very simple, it allows researchers to create variations that reveal a great deal about a
newborn’s cognitive ability. The trick is simply to change the stimulus in controlled ways to see if the baby “notices
the difference.” Research using the habituation procedure has found that babies can notice changes in colors, sounds,
and even principles of numbers and physics. For instance, in one experiment reported by Karen Wynn (1995), [9] 6-
month-old babies were shown a presentation of a puppet that repeatedly jumped up and down either two or three
times, resting for a couple of seconds between sequences (the length of time and the speed of the jumping were
controlled). After the infants habituated to this display, the presentation was changed such that the puppet jumped a
different number of times. As you can see in Figure 6.3 "Can Infants Do Math?", the infants’ gaze time increased when
Wynn changed the presentation, suggesting that the infants could tell the difference between the number of jumps.
Figure 6.3Can Infants Do Math?