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Article Excerpt
Individual differences in child temperament have been associated with individual differences in language development. Similarly, relationships have been reported between early nonverbal social communication (joint attention) and both temperament and language. The present study examined whether individual differences in joint attention might mediate temperament-language relationships. Temperament, language, and joint attention were assessed in 51 21-month-aids. Results indicated an inverse relationship between aspects of temperamental difficulty, including low executive control and high negative affect, and language development. Temperamental aspects of negative affect were also inversely predictive of joint attention. However, the utility of a model in which joint attention mediates the relationship between temperament and language during the second year was not supported.
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A growing body of literature has revealed relationships between children's temperament and their language development. Researchers have linked specific temperamental dimensions such as attention span and positive emotionality to both productive and receptive language, and they have done so repeatedly across multiple lab settings (Dixon & Smith, 2000; Karrass, 2002; Matheny, 1989; Morales et al., 2000a; Slomkowski, Nelson, Dunn, & Plomin, 1992). The general finding has been that children with aspects of temperamental easiness (i.e., affective positivity, long attention span) tend to be relatively linguistically advanced. Although the correlational nature of these studies makes it premature to draw conclusions with respect to directions of effect, a bidirectional influence seems reasonable. For example, just as heightened linguistic sophistication may contribute to ease of interpersonal communication and relatively positive affect as a result of successful communication, so too might temperamental positive affect contribute to increased opportunities for language acquisition. In the present study, we focus on the potential impact of temperament on language and consider ways in which temperament might be expected to influence language development.
Following the assumption that temperament contributes to language development, we must ask how it would do so. Rieser-Danner (2003) has postulated that temperament may have both direct and indirect impacts on language and cognitive functioning. In terms of a direct route of influence, children's difficult temperaments might simply limit the extent to which they can process linguistically relevant information during language acquisition events. This possibility is consistent with Rothbart and Bates (1998), who suggest that the attentional components of temperament form part of an overarching behavioral control system, which, as a function of anterior brain maturation, becomes increasingly weighted through early development with modulating dimensions of temperament associated with emotionality. Thus, when children are very high in general negative affectivity, a relatively greater burden is placed on their behavioral control systems, which must regulate this negative affectivity. The end result is fewer resources available for linguistically relevant activities such as paying attention to word-referent associations when learning novel labels. Consistent with Rothbart and Bates' hypothesis, a number of studies have reported that children who possess greater negative affect, higher response intensity, and lower tolerance for change of routine do in fact exhibit relatively short attention spans (e.g., Gartstein & Rothbart, 2003; Karrass & Braungart-Rieker, 2003; Smith et al., 1997), and these children also tend to have smaller vocabularies (Dixon & Smith, 2000).
An alternative route of influence follows from the possibility that some aspects of children's temperament might indirectly contribute to language by influencing the formation of the social relationships that are relevant for language acquisition. That is, the kind and duration of interpersonal exchanges entered into by temperamentally difficult children may be different than those entered into by easygoing children, and these interpersonal relationships may have differential consequences for language acquisition (cf. Rieser-Danner, 2003). The temperament to language route of influence in this case is indirect to the extent that temperament is mediated by relationship quality.
These pathways of influence are not necessarily mutually exclusive, and both may be partially responsible for contributing to language development. However, to our knowledge only two studies have directly examined either route of influence, and both of these have focused explicitly on the direct route (Dixon & Salley, in press; Dixon, Salley, & Clements, 2006). The premise of these studies was that because children's temperament cannot be manipulated directly, the next best thing would be to manipulate the environment in a way that would tap into children's temperament in theoretically relevant ways. Thus, in a laboratory setting, Dixon and colleagues distracted children while simultaneously teaching them novel words, with the expectation that the effect of the distracters on word learning would vary as a function of children's temperaments. Results of these studies were consistent with the direct-route approach. Children with the longest attention spans (as rated by either neutral observers or mother report) were least affected by the distracters and most likely to learn the novel words.
Importantly, other research suggests the importance of taking social relationships into account when exploring temperament-cognition associations. For example, Karrass and Braungart-Rieker (2004) reported that correlations between 1-year temperamental distress to novelty and 3-year IQ were moderated by security of mother-child attachment. Historically, temperament and language development have both been associated with social development (e.g., Carson, Klee, Perry, Muskina, & Donaghy, 1998; Thomas, Chess, & Birch, 1968), which raises the possibility that easygoing children are relatively socially skilled and are well positioned to establish high-quality social relationships that would place them at a linguistic advantage.
One aspect of children's social skills that may play a particularly central role in mediating temperament-language relationships is children's proclivity for engaging in joint attention. Researchers have consistently reported relationships throughout infancy and toddlerhood between joint attention and both language development (Markus, Mundy, Morales, Delgado, & Yale, 2000; Mundy & Gomes, 1998) and temperament (Kasari, Sigman, Mundy, & Yirmiya, 1990; Vaughan et al., 2003). Thus, there is evidence that joint attention may play a mediating role in the temperament-language relationship. However, to our knowledge no published research has explored whether correlations between temperament and language are a byproduct of their common relationship with joint attention.
Joint attention as a means of nonverbal social communication is theorized to tap into social, emotional, and cognitive domains of development. It also reliably predicts a variety of sociodevelopmental outcomes, including IQ, social adaptation, behavioral regulation, and language development in both typically and atypically developing populations (Sheinkopf, Mundy, Claussen, & Willoughby, 2004). In terms of its developmental significance, joint attention has been characterized as a specialized form of attention sharing and nonverbal communication that emerges as children first engage in eye-to-eye gaze with social partners, and it develops as children and their social partners coordinate attention toward common objects or events. Joint attention has been divided into two basic categories: (1) responding to joint attention (RJA) occurs when one follows the direction of eye gaze, head turn, or pointing gesture of a social partner (Mundy, Hogan, & Doehring, 1996), whereas (2) initiating joint attention (IJA) occurs when one points or looks at an interesting object or event while alternating gaze between the object and a social partner (Mundy et al., 1996). Joint attention is most often operationally defined either by the amount of time spent in mutual object engagement in naturalistic settings or by experimentally induced behaviors (i.e., eye gaze following or pointing in response to experimenter prompts).
Researchers have primarily focused on understanding how joint attention facilitates language development (Carpenter, Nagell, & Tomasello, 1998; Dunham & Dunham, 1992; Dunham, Dunham, & Curwin, 1993; Morales et al., 2000a; Tomasello & Farrar, 1986), and it is easy to conceptualize how it might do so. Baldwin (1995), for example, demonstrated that when 18-month-old children and an adult experimenter were looking at two different novel objects and the adult applied a novel word to her own object, children would learn the novel label for the experimenter's object rather than identifying the label with their own object. In this case, children had to attend to the experimenter's attentional focus in order to learn the target word-referent mapping.
In a longitudinal study of joint attentional behaviors from 6 to 24 months, Morales et al. (2000b) found that responding to joint attention...
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