Understanding Psychology (10th Ed)

 
Module 37 
Infancy and Childhood 
395
rate. This phenomenon is known as  habituation,  the decrease in the response to a 
stimulus that occurs after repeated presentations of the same stimulus. By studying 
habituation, developmental psychologists can tell when a child who is too young to 
speak can detect and discriminate a stimulus (Grunwald et al., 2003; Hannon & 
Johnson, 2005; del Rosal, Alonso, & Moreno, 2006).
Researchers have developed many other methods for measuring neonate and 
infant perception. One technique, for instance, involves babies sucking on a nipple 
attached to a computer. A change in the rate and vigor with which the babies suck 
helps researchers infer that babies can perceive variations in stimuli. Other 
approaches include examining babies’ eye movements and observing which way 
babies move their heads in response to a visual stimulus (George, 1999; Franklin, 
Pilling, & Davies, 2005). 
Through the use of such research techniques, we now know that infants’ visual 
perception is remarkably sophisticated from the start of life. At birth, babies prefer 
patterns with contours and edges over less distinct patterns, indicating that they can 
respond to the confi guration of stimuli. Furthermore, even newborns are aware of 
size constancy because they are apparently sensitive to the phenomenon by which 
objects stay the same size even though the image on the retina may change size as 
the distance between the object and the retina varies (Norcia et al., 2005; Moore, 
Goodwin, & George, 2007). 
In fact, neonates can discriminate facial expressions—and even imitate them. As 
you can see in Figure 2, newborns can produce a good imitation of an adult’s expres-
sions. Even very young infants, then, can respond to the emotions and moods that 
their caregivers’ facial expressions reveal. This capability provides the foundation for 
social interaction skills in children (Meltzoff, 1996; Lavelli & Fogel, 2005; Grossmann, 
Striano, & Friederici, 2007). 
Other visual abilities grow rapidly after birth. By the end of their fi rst month, 
babies can distinguish some colors from others; after 4 months they can focus on