Precursors of a theory of mind: A longitudinal study Cristina Colonnesi 1 *, Carolien Rieffe 2 , Willem Koops 3 and Paola Perucchini 4 1 Faculty of Social and Behavioral Science, University of Amsterdam, Amsterdam, The Netherlands 2 Developmental Psychology, Leiden University, Leiden, The Netherlands 3 Department of Social Sciences, University of Utrecht, Utrecht, The Netherlands 4 Department of Educational Science, University of Rome ‘Roma Tre’, Rome, Italy The study examined whether the pointing gesture and intentional understanding abilities at 12 and 15 months of age predict the later understanding of perception and intention, as well as the ability to explain others’ actions in a psychological way at 39 months of age. Thirty-five infants (18 girls) were administered pointing and intention- understanding tasks at the age of 12 and 15 months. Children were again evaluated at the age of 39 months with perception and intention tasks, and a psychological explanation task. Results showed that only 12-month-olds’ comprehension of the pointing gesture with an imperative motive contributed to the prediction of later understanding of perception and mentalistic explanations of actions. Moreover, the ability of 12- and 15-month-olds to understand intentions contributed to the prediction of later preschool understanding of perceptions and intentions. These results indicate that a developmental trajectory in children’s understanding of mental states from infancy to childhood is present, but depends on the level of engagement and communication that are required to perform these tasks. Over the last 10 years, theory of mind research has been increasingly directed towards its earlier development during the first 2 years of life, aiming to find a developmental progression from infancy to childhood. Many socio-cognitive abilities in the second year of life could set the base for theory of mind development (Carpenter, Nagell, & Tomasello, 1998; Tomasello, Carpenter, Call, Behne, & Moll, 2005). Two of these are joint attention behaviour (Carpendale & Lewis, 2006 for a review) and understanding of others’ intentions (Meltzoff, 1995). In this study, we will consider to what extent these two features in infancy might contribute to children’s later theory-of-mind functioning. * Correspondence should be addressed to Dr Cristina Colonnesi, Faculty of Social and Behavioral Science, University of Amsterdam, Amsterdam 1018 VZ, The Netherlands (e-mail: c.colonnesi@uva.nl). The British Psychological Society 561 British Journal of Developmental Psychology (2008), 26, 561–577 q 2008 The British Psychological Society www.bpsjournals.co.uk DOI:10.1348/026151008X285660