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-olds. 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.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 seem 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 article, 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 suggested 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 Correspondence concerning this article should be addressed to Wallace Dixon, Depa...