Factors Contributing to Variations in Rate of Language Acquistion
Since the critical period for language development occurs within the first thirty-six months of a child’s life, significant language delay may indicate specific medical or cognitive problems. Beyond medical problems, there are several factors that could modify the rate of normal language production. We review these factors in the following discussion.
Are there differences in the rate and ways that boys and girls develop language fluency and proficiency? This question reflects another facet of the ongoing nature versus nurture debate. Observational research consistently reveals that a majority of girls talk earlier and talk more than the majority of boys. It is also true that the majority of late talkers are young boys (Healy, 1997; Kalb & Namuth, 1997). However, it is difficult to determine whether differences in the rate of language acquisition are biological or if biological differences are exaggerated by social influences. There is evidence for both views. For example, neurobiological research offers graphic images that illustrate how men’s and women’s brains process language somewhat differently (Corballis, 1991; Moir & Jessel, 1991). Though this research appears to support nature as the dominant factor in language differences, it is also important to consider how powerful a role nurture plays. Experimental research consistently documents differential treatment of infants based on gender. In other words, men and women tend to cuddle, coo at, and engage in lengthy face-to-face conversations with baby girls. Yet with baby boys, adults are likely to exhibit “jiggling and bouncing” behaviors but are not as likely to engage in sustained face-to-face verbal interactions. Perhaps girls talk earlier and talk more because they receive more language stimulation (Huttenlocher, 1991).
Numerous studies have long documented the differences in the rate of language acquisition and the level of language proficiency between low and middle socioeconomic families (Hart & Risley, 1995; Morisset, 1995; Walker, Greenwood, Hart, & Carta, 1994). These studies found that children, especially males, from low-income homes were usually somewhat slower to use expressive language than children from middle-income homes. These findings likely reflect social-class differences both in language use in general and in parent–child interaction patterns. For example, Betty Hart and Todd Risley (1995) estimate that by age four, children from professional families have had a cumulative total of 50 million words addressed to them, whereas children from welfare families have been exposed to only 13 million words. The children from professional families have had more than three times the linguistic input than welfare families’ children; this gives them a tremendous advantage in language acquisition.
Results of long-term observations of middle-income and lower-income families concluded that all mothers spent a great deal of time nurturing their infants (e.g., touching, hugging, kissing, and holding), but that there were differences in the way mothers verbally interacted with their children. Middle-income mothers spent a great deal more time initiating verbal interactions and usually responded to and praised their infants’ vocal efforts. Middle-income mothers were also more likely to imitate their infants’ vocalizations. These verbal interactions stimulate neural-synapse networks that foster expressive and receptive language. It is still unclear why lower-income mothers do not engage their children in verbal interactions at the same level as middle-income mothers. The authors of these studies speculate that this may be a reflection of social-class differences in language use in general.
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