The Contribution of Symbolic Skills to the Development of an Explicit Theory of Mind Angeline S. Lillard University of Virginia Robert D. Kavanaugh Williams College Theorists have speculated about the symbolic underpinnings of theory of mind (ToM), but no study has examined them across the main developmental span of ToM. Here, the onset of symbolic understandings in three domains (pretend play, language, and understanding representations) and ToM was examined. Fifty- eight children were tested on batteries of tasks four times from ages 2.5 to 5 years. Some significant interrela- tions among variables were seen at each age level. Canonical correlation analysis found that a subset of the symbolic variables was significantly related to ToM at ages 4 and 5, providing the best evidence to date that ToM is undergirded by a symbolic element that also supports language, pretend play, and representational understanding. A major achievement of early childhood is realizing that unobservable mental states, such as thoughts, beliefs, and emotions, underlie much of human behavior, an achievement referred to as a theory of mind (ToM; Premack & Woodruff, 1978). The importance of developing ToM, at least in Western societies, cannot be overestimated (Wellman, 2011). It is essential in communities that rely heavily on the exchange of information, ideas, and points of view through shared discourse. Developmentally, ToM represents a substantial change in the way that children engage with others. Put simply, a well-developed ToM is the key to realizing that behavior is motivated. People do not act without cause, but rather behave as they do because of what they think, know, feel, or believe. Although we know a lot about ToM, such as what develops when (Wellman, 2011), that from ages 3 to 6 its latent factor structure is stable (Hughes, Ensor, & Marks, 2011), and that it predicts conceptually related factors like mental state talk, friendship interactions, and sociometric status (Capage & Watson, 2001; Hughes et al., 2011; Razza & Blair, 2009), much is still to be explained regarding how ToM develops. Some environmental features are important. For example, parents’ atten- tion to mental states appears to contribute to ToM (Meins et al., 2002; Ruffman, Perner, & Parkin, 1999), and having different-aged siblings or class- mates is also often (but not always) associated with earlier development of ToM (Cassidy, Fineberg, Brown, & Perkins, 2005; Cutting & Dunn, 1999; Lewis, Freeman, Kyriakidou, Maridaki-Kassotaki, & Berridge, 1996; Perner, Ruffman, & Leekam, 1994; Ruffman, Perner, Naito, Parkin, & Clements, 1998; Wang & Su, 2009). Specific child characteristics are also associated with earlier development of ToM. Three child factors that have been repeatedly and concurrently correlated with ToM are children’s level and frequency of pretend play (see Lillard et al., 2013), language ability (Astington & Baird, 2005; Hughes et al., 2005), and executive function (Carlson & Moses, 2001; Hughes, 1998). Two of these abilities—pretend play and language—are considered representational or symbolic. This study asks whether symbolic abilities used in pretending and language might actually undergird ToM. We are particularly concerned with an explicit ToM— revealed when a child expressly acknowledges that the world can be represented in multiple ways— rather than implicit ToM examined with looking time procedures (Apperly & Butterfill, 2009). Both authors are affiliated with the Departments of Psychol- ogy. We thank Joseph Lucia, Reka Dar oczi, Leigh Owens, Mary Lindeke, Kyle Skor, and Elise Piazza for their assistance with data collection; John Nesselroade and Matt Lerner for statistical advice; and Paul Harris for comments on an earlier draft of this manuscript. This research was supported in part by NSF Grant 1024293, a Brady Education Foundation Grant, and a University of Virginia Sesqui award to ASL, and a Williams College Grant to RK. Correspondence concerning this article should be addressed to Angeline S. Lillard, Department of Psychology, University of Virginia, P.O. Box 400400, Charlottesville, VA 22904. Electronic mail may be sent to Lillard@virginia.edu. © 2014 The Authors Child Development © 2014 Society for Research in Child Development, Inc. All rights reserved. 0009-3920/2014/xxxx-xxxx DOI: 10.1111/cdev.12227 Child Development, xxxx 2014, Volume 00, Number 0, Pages 1–17