Читать книгу Lifespan Development - Tara L. Kuther - Страница 271

At 3 months of age, Baby Lourdes can lift and support her upper body with her arms when on her stomach. She grabs and shakes toys with her hands and enjoys playing with other people. Lourdes’s pediatrician tells her parents that her development is right on track for babies her age and that she shows typical levels of infant intelligence. Standardized tests permit the pediatrician to determine Lourdes’s development relative to other infants her age.

The most often used standardized measure of infant intelligence is the Bayley Scales of Infant Development III (BSID-III), commonly called “Bayley-III” (see Figure 5.7). This test is appropriate for infants from 1 month through 42 months of age (Bayley, 1969, 2005). The Bayley-III consists of five scales: three consisting of infant responses and two of parent responses. The Motor Scale measures gross and fine motor skills, such as grasping objects, drinking from a cup, sitting, and climbing stairs. The Cognitive Scale includes items such as attending to a stimulus or searching for a hidden toy. The Language Scale examines comprehension and production of language, such as following directions and naming objects. The Social-Emotional Scale is derived from parental reports regarding behavior such as the infant’s responsiveness and play activity. Finally, the Adaptive Behavior Scale is based on parental reports of the infant’s ability to adapt in everyday situations, including the infant’s ability to communicate, regulate his or her emotions, and display certain behavior.

The Bayley-III provides a comprehensive profile of an infant’s current functioning, but the performance of infants often varies considerably from one testing session to another (Bornstein, Slater, Brown, Roberts, & Barrett, 1997). Scores vary with infants’ states of arousal and motivation. This suggests that pediatricians and parents must exert great care in interpreting scores—particularly poor scores—because an infant’s performance may be influenced by factors other than developmental functioning. Alternatively, some researchers have argued that perhaps the variability in Bayley-III scores from one occasion to another suggests that intelligence itself is variable in infancy (Bornstein et al., 1997). Regardless, the low test–retest reliability (see Chapter 1) means that infants who perform poorly on the Bayley-III should be tested more than once.

Although Bayley-III scores offer a comprehensive profile of an infant’s abilities, scores do not predict performance on intelligence tests in childhood (dos Santos, de Kieviet, Königs, van Elburg, & Oosterlaan, 2013; Rose & Feldman, 1995). Even Nancy Bayley, who invented the Bayley Scales, noted in a longitudinal study (1949) that infant performance was not related to intelligence scores at age 18. Why is infant intelligence relatively unrelated to later intelligence? Consider what is measured by infant tests: perception and motor skills, responsiveness, and language skills. The abilities to grasp an object, crawl up stairs, or search for a hidden toy—items that appear on the Bayley-III—are not measured by childhood intelligence tests. Instead, intelligence tests administered in childhood examine more complex and abstract abilities such as verbal reasoning, verbal comprehension, and problem solving.

Figure 5.7 Bayley-III Scales (BSID-III)

Infant assessment tests, such as the BSID-III, examine cognitive, language, social-emotional, and motor abilities, such as infants’ skill in manipulating objects.

Source: Cliff Moore / Science Source

If the Bayley-III does not predict later intelligence, why administer it? Infants whose performance is poor relative to age norms may suffer from serious developmental problems that can be addressed. The intellectual abilities measured by the Bayley-III are critical indicators of neurological health and are useful for charting developmental paths, diagnosing neurological disorders, and detecting intellectual disabilities in infants and toddlers. Thus, the Bayley-III is primarily used as a screening tool to identify infants who can benefit from medical and developmental intervention. As discussed in the accompanying Brain and Biological Influences on Development feature, contextual conditions, especially exposure to poverty, can place some infants and children at risk for poor cognitive development and lower IQ.