Mother and Infant Talk About Mental States Relates to Desire Language and Emotion Understanding Mele Taumoepeau and Ted Ruffman University of Otago This study assessed the relation between mother mental state language and child desire language and emotion understanding in 15 – 24-month-olds. At both time points, mothers described pictures to their infants and mother talk was coded for mental and nonmental state language. Children were administered 2 emotion un- derstanding tasks and their mental and nonmental state vocabulary levels were obtained via parental report. The results demonstrated that mother use of desire language with 15-month-old children uniquely predicted a child’s later mental state language and emotion task performance, even after accounting for potentially con- founding variables. In addition, mothers’ tendency to refer to the child’s over others’ desires was the more consistent correlate of mental state language and emotion understanding. This study assesses the relation between mother mental state language, and desire language and emotion understanding in 1 – 2-year-old children. There is a growing body of evidence supporting a social interactionist framework in which family in- put facilitates the development of children’s social understanding (Carpendale & Lewis, 2004; Dunn, Brown, Slomkowski, Tesla, & Youngblade, 1991; Jenkins, Turrell, Kogushi, Lollis, & Ross, 2003; Nel- son, 2003; Perner, Ruffman, & Leekam, 1994). Social understanding in this context refers to how children come to understand others’ thoughts, feelings, and desires as different from their own and thus enables a child to interpret the way people will act, behave, and feel. Much of this research can be situated within Vygotsky’s thesis that society and culture play an important role in facilitating the acquisition of higher order mental functioning (Vygotsky, 1978). In par- ticular, the cooperative task of conversation enables the child to internalize ways of thinking through exposure to conversation about ‘‘thinking’’ with adult partners (Astington, 1996; Symons, 2004). Thus, central to this theory is the pivotal role of a child’s exposure to mental state language. Indeed, research with older preschoolers suggests that pa- rental use of mental state language plays an impor- tant role in the development of false belief (Cutting & Dunn, 1999; Meins & Fernyhough, 1999; Ruffman, Slade, & Crowe, 2002), emotion (Dunn, Brown, & Beardsall, 1991), and general theory of mind (Ruff- man et al., 2002) understanding. Although the vast majority of this research, has focused on children aged 3 – 5 years, very little has examined mental state language directed at infants (although see Meins & Fernyhough, 1999). This is important, first, because the period of language de- velopment before 2 years plays host to a burgeoning of general vocabulary and conversational develop- ment. Second, research indicates that some aspects of theory of mind are in place very early in develop- ment. Specifically, theory-theories such as that of Wellman (1990) propose that 2-year-olds progress from understanding a person’s actions using a sim- ple-desire psychology to understanding that a per- son’s beliefs about the world, true or otherwise, frame how a person acts and feels. Likewise, Perner (1991) proposed that children progress from being situation theorists, which initially allows an under- standing of desire to being capable of meta-repre- sentation, which allows an understanding of belief. In contrast, simulation theory proposes that children r 2006 by the Society for Research in Child Development, Inc. All rights reserved. 0009-3920/2006/7702-0015 The research was conducted during tenure of a Health Research Council of New Zealand, Pacific Health Research Postgraduate Award to Mele Taumoepeau. The MacBrain face stimulus set used in this study was obtained from the MacArthur Foundation Research Network on Early Ex- perience and Brain Development. Development of the MacBrain Face Stimulus Set was overseen by Nim Tottenham and supported by the John D. & Catherine T. MacArthur Foundation Research Network on Early Experience and Brain Development. Please contact Nim Tottenham at tott0006@tc.umn.edu for more infor- mation concerning the stimulus set. We owe special thanks to the children and parents who partic- ipated in the study, to Kirstie Morgan and Anna Janssen for help with the transcribing and coding, and to two anonymous re- viewers for their insightful comments. Correspondence concerning this article should be addressed to Mele Taumoepeau, Department of Psychology, University of Ot- ago, Box 56, Dunedin, New Zealand. Electronic mail may be sent to mele@psy.otago.ac.nz. Child Development, March/April 2006, Volume 77, Number 2, Pages 465 – 481