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How do researchers study infant perception? The simplest method is through preferential looking tasks, experiments designed to determine whether infants prefer to look at one stimulus or another. For example, consider an array of black and white stripes. As shown in Figure 4.12, an array with more stripes (and therefore, many more narrow stripes) tends to appear gray rather than black and white because the pattern becomes more difficult to see as the stripes become more narrow. Researchers determine infants’ visual acuity, sharpness of vision or the ability to see, by comparing infants’ responses to stimuli with different frequencies of stripes because infants who are unable to detect the stripes lose interest in the stimulus and look away from it.

Description

Figure 4.12 Visual Acuity

Researchers and pediatricians use stimuli such as the Teller Acuity Cards illustrated here to determine what infants can see. Young infants attend to stimuli with wider lines and stop attending as the lines become smaller.

Source: Leat, Yadev, and Irving (2009).

Another method of studying infant perception relies on infants’ capacity for habituation, a gradual decline in the intensity, frequency, or duration of a response to an unchanging stimulus. For example, to examine whether an infant can discriminate between two stimuli, a researcher presents one until the infant habituates to it. Then a second stimulus is presented. If dishabituation, or the recovery of attention, occurs, it indicates that the infant detects that the second stimulus is different from the first. If the infant does not react to the new stimulus by showing dishabituation, it is assumed that the infant does not perceive the difference between the two stimuli. The habituation method is very useful in studying infant perception and cognition and underlies many of the findings discussed in this chapter.

Operant conditioning is the basis for a third method researchers use to study perception in infants. Recall from Chapter 1 that operant conditioning entails learning behaviors based on their consequences, whether they are followed by reinforcement or punishment. Behaviors increase when they are followed by reinforcement and decrease when they are followed by punishment. Research employing this method has shown that newborns will change their rate of sucking on a pacifier, increasing or decreasing the rate of sucking, in order to hear a tape recording of their mother’s voice, a reinforcer (Moon et al., 1993). Other research shows that newborns will change their rate of sucking to see visual designs or hear human voices that they find pleasing (Floccia et al., 1997). Researchers have found that premature infants and even third-trimester fetuses can be operantly conditioned (Dziewolska & Cautilli, 2006; Thoman & Ingersoll, 1993). For example, a 35-week-old fetus will change its rate of kicking in response to hearing the father talk against the mother’s abdomen, suggesting that hearing begins in the womb (Dziewolska & Cautilli, 2006).