Running Head : Children ’ s Causal Categorization Causal Categorization in Children and Adults

Two experiments examined the impact of causal relations between features on categorization by adults and 5-6-year-old children. Participants learned about artificial categories containing instances with two causally related features and two non-causal features. They then selected the most likely category member from a series of novel test pairs. Classification patterns and logistic regression were used to diagnose the presence of independent effects of causal coherence, causal status and relational centrality. Adult classification was driven primarily by coherence when causal links were deterministic (Experiment 1), but showed additional influences of causal status and centrality when links were probabilistic (Experiment 2). Children’s classification was based primarily on causal coherence in both cases. These results suggest that the generative model [Rehder, B. (2003). A causalmodel theory of conceptual representation and categorization. Journal of Experimental Psychology: Learning, Memory, and Cognition, 29, 1141-1159] provides a good account of causal categorization in both children and adults. Children’s Causal Categorization 3 It is well established that causal knowledge plays an important role in adult categorization and property induction (see Sloman, 2005 for a review). Adults are more likely to assign an object to a category if it has the same causal features (features which causally contribute to the presence of other features) as known category members (Ahn, Kim, Lassaline, & Dennis, 2000b; Rehder & Hastie, 2001; Rehder, 2003a; Sloman, Love, & Ahn, 1998; see Ahn & Kim, 2001 and Rehder, 2010 for reviews). They often predict the features of category members on the basis of causal relations (Rehder & Burnett, 2005; see also Sloman & Lagnado, 2005; Waldmann & Hagmeyer, 2005), and use those inferences to establish category membership (Chaigneau, Barsalou, & Sloman, 2004; Hampton, Estes, & Simmons, 2007; Rehder & Kim, 2009). Finally, they inductively generalize properties from a familiar instance to a novel target item if the base and target have the same causal features (Hayes & Thompson, 2007; Lassaline, 1996; Rehder & Hastie, 2004; Rehder, 2006; 2009). The role of causal knowledge in children’s categorization decisions, however, remains less clear. The prevailing view for many decades was that young children are more likely than older children or adults to categorize on the basis of the perceptual similarity between known category members and novel objects, paying relatively little attention to complex relations like causality (Piaget & Inhelder, 1973; Sloutsky & Fisher, 2004; Springer 2001). This view has been challenged by a variety of recent developmental findings (see Hayes, 2006 for a review). For example, it has been found that when perceptually dissimilar objects have similar causal powers (i.e., give rise to similar effects) preschool children are likely to assign them to the same category (Gopnik, Glymour, Sobel, Schulz, Kushnir, & Danks, 2004). Opfer and Bulloch (2007) have shown that when salient causal relations conflict with perceptual similarity, 6-year-olds often prefer to categorize on the basis of causal relations (also see Carmichael & Hayes, 2001; Hayes, Foster, & Gadd, 2003). Finally, Ahn, Gelman, Amsterlaw, Hohenstein and Kalish (2000a) taught 7to 9-year-olds that one category feature was the cause of two others. They told children, for example, that a fictitious animal called taliboos had promicin in their nerves, thick bones, and large eyes, and that the thick bones and large eyes were caused by the promicin (this network of causal relations is depicted in Figure 1A). Ahn et al. presented children with two animals, one missing only the cause feature (e.g., promicin) and the other missing Children’s Causal Categorization 4 only one of the effect features (e.g., thick bones or large eyes) and asked which was the more likely category member. Children preferred the alternative with a missing effect over the one with the missing cause (i.e., they preferred the item on the right hand side over the item on left in Figure 1B). Meunier and Cordier (2009) found a similar effect with 5-year-olds using a related design. This evidence shows that by five years of age (and perhaps earlier) children can and do use causal relations as a basis for categorizing. Two critical issues, however, remain unresolved. First, it is still unclear exactly how knowing about causal relations between object features affects the way that children use those features to categorize (we present several possibilities below). Second, the nature and extent of developmental change in causal categorization remains unclear. The current study addresses each of these issues. Promicin Thick bones