Lifespan Development. Tara L. Kuther

effect of high SES contexts. Chronic poverty is especially damaging because the neurological and cognitive deficits accumulate over childhood (Dickerson & Popli, 2016). One way in which poverty affects development is through the quality of parent–infant interactions and infants’ exposure to language (Hackman, Gallop, Evans, & Farah, 2015). Infants in higher SES homes are talked to more and the speech they hear is often more stimulating and supportive of language development than is the case in lower SES homes (Fernald, Marchman, & Weisleder, 2013; Sheridan, Sarsour, Jutte, D’Esposito, & Boyce, 2012).

      Description

      Figure 5.8 Percentage of Children in Low-Income and Poor Families by Race/Ethnicity, 2016

      Source: Koball & Jiang (2018).

      Poverty is also thought to affect children’s outcomes indirectly by contributing to household chaos, a combination of household instability and disorder (Berry et al., 2016). Children reared in economic uncertainty are more likely to experience disruptions in home settings and relationships through household moves and adults moving in and out of the home (Pascoe, Wood, Duffee, & Kuo, 2016). Impoverished environments often include household crowding, lack of structure, and excessive ambient noise in the home or neighborhood (Evans & Kim, 2013). Infants and children reared in environments of household chaos may be overwhelmed by stimulation combined with little developmentally appropriate support with negative effects for cognitive development. The effects of a chaotic home environment begin early. For example, a chaotic environment has been shown to negatively affect visual processing speed for complex stimuli in 5.5-month-old infants (Tomalski et al., 2017). Poverty has early effects on children’s brain development that increase over time with lifelong implications for cognitive and language development.

      What Do You Think?

      1 Infants and children reared in poverty face many contextual risks to development. Their contexts may also offer opportunities for resilience. Identify factors within the family and home that can promote the development of infants and children who are exposed to poverty.

      2 How might the extended family, neighborhood, and community help to buffer the effects of challenging environments on development?

      Information processing abilities can be assessed in simple ways that allow us to study intelligence in infants who are too young to tell us what they think and understand. For example, infants’ visual reaction time (how quickly they look when shown a stimulus) and preference for novelty (the degree to which they prefer new stimuli over familiar ones) are indicators of attention, memory, and processing speed and have been shown to predict intelligence in childhood and adolescence (Fagan, 2011). Habituation tasks also provide information about the efficiency of information processing because they indicate how quickly an infant learns: Infants who learn quickly look away from an unchanging stimulus (or habituate) rapidly. Longitudinal studies suggest that infants who are fast habituators score higher on measures of intelligence in childhood and adolescence than do those who are slower habituators (Kavšek, 2013; Rose, Feldman, & Jankowski, 2012). One study demonstrated that, compared with average and slow habituators, infants who were fast habituators had higher IQs and higher educational achievement when they were followed up 20 years later in emerging adulthood.

      Many other studies confirm that infant information processing abilities are associated with measures of intelligence throughout life. For example, working memory and visuospatial short-term memory in infancy are associated with IQ in fourth- and fifth-grade children (Giofrè, Mammarella, & Cornoldi, 2013). Working memory and processing speed are also associated with intelligence in children and adults (Redick, Unsworth, Kelly, & Engle, 2012; Rose, Feldman, Jankowski, & Van Rossem, 2012; Sheppard, 2008). Information processing skills in infancy are effective predictors of intelligence in childhood; however, these findings are generally the result of laboratory research. Although pediatricians might test an infant’s attention and habituation as part of an examination, there is no standardized information processing test of intelligence to apply to infants comparable to the Bayley-III.

      Thinking in Context 5.3

      1 Thinking back to the continuity–discontinuity theme of development (see Chapter 1), would you say that intelligence represents an example of continuous or discontinuous change? Explain your answer.

      2 Why is infant intelligence a poor predictor of later intelligence?

      3 How might contextual factors, such as home environment and experiences, influence the skills measured by infant intelligence tests such as the Bayley-III?

      Language Development in Infancy and Toddlerhood

      “You just love to hear Mommy talk, don’t you?” Velma asked as newborn Jayson stared up at her. Can Jayson attend to his mother? Is Jayson interested in his mother’s speech? As described in Chapter 4, hearing emerges well before birth, and evidence suggests that newborns can recall sounds heard in the womb (Dirix, Nijhuis, Jongsma, & Hornstra, 2009). Developing the ability to use language is a critical step in infancy and toddlerhood; it has important implications for the child’s cognitive, social, and emotional development. Gaining the ability to use words to represent objects, experience, thoughts, and feelings permits children to think and to communicate with others in increasingly flexible and adaptive ways.

      Early Preferences for Speech Sounds

      Newborn infants are primed to learn language. Recall from Chapter 4 that neonates naturally attend to speech and prefer to hear human speech sounds, especially their native language, as well as stories and sounds that they heard prenatally (May, Gervain, Carreiras, & Werker, 2018). Infants naturally notice the complex patterns of sounds around them and organize sounds into meaningful units. They recognize frequently heard words, such as their names. By 4½ months of age, infants will turn their heads to hear their own names but not to hear other names, even when the other names have a similar sound pattern (e.g., Annie and Johnny) (Mandel, Jusczyk, & Pisoni, 1995). At 6 months of age, infants pay particular attention to vowel sounds and, at 9 months, consonants (Kuhl, 2015).

      Although infants can perceive and discriminate sounds that comprise all human languages at birth, their developing capacities and preferences are influenced by context (Hoff, 2015). For example, the Japanese language does not discriminate between the consonant sounds of “r” in rip and “l” in lip. Japanese adults who are learning English find it very difficult to discriminate between the English pronunciations of these “r” and “l” sounds, yet up until about 6 to 8 months of age, Japanese and U.S. infants are equally able to distinguish these sounds. By 10 to 12 months, however, discrimination of “r” and “l” improves for U.S. infants and declines for Japanese infants. This likely occurs because U.S. infants hear these sounds often, whereas Japanese infants do not (Kuhl et al., 2006). As they are exposed to their native language, they become more attuned to the sounds (and distinctions between sounds) that are meaningful in their own language and less able to distinguish speech sounds that are not used in that language (Werker, Yeung, & Yoshida, 2012). Native-language discrimination ability between 6 and 7 months predicts the rate of language growth between 11 and 30 months (Kuhl, 2015).

      Infants’ speech discrimination abilities remain malleable in response to the social context (Kuhl, 2016). In one study, Kuhl and her colleagues exposed 9-month-old English-learning American infants to 12 live interaction sessions with an adult speaker of Mandarin Chinese over the course of 4 to 5 weeks (Kuhl, Tsao, & Liu, 2003). After the sessions, the infants were tested on a Mandarin phonetic contrast that does not occur in English. The infants discriminated