24-Month-Olds Engage in Relational Causal Reasoning

24-Month-Olds Engage in Relational Causal Reasoning Caren M. Walker (caren.walker@berkeley.edu) Department of Psychology, University of California, Berkeley, 3210 Tolman Hall, Berkeley, CA 94720 USA Alison Gopnik (gopnik@berkeley.edu) Department of Psychology, University of California, Berkeley 3210 Tolman Hall, Berkeley, CA 94720 USA Abstract Children make inductive inferences about the causal properties of individual objects from a very young age. When can they infer higher-order relational properties - a task that has proven difficult for non-human primates? In two experiments, we examined 18- 24-month-old infants’ relational inferences using a causal version of a relational match-to-sample task. Results suggest that by 21-24 months of age, infants are able to infer a relational causal principle from just a few observations and use this inference to guide their own subsequent actions and bring about a novel causal outcome. Findings are considered in light of recent discussion about the nature of relational and causal reasoning, and their evolutionary origins. Keywords: Cognitive development; infancy; relational reasoning; causal learning; inference Introduction Learning about causal relationships is one of the most important and challenging problems young humans face. Causal knowledge allows you to act on the world – if you know A causes B, you can act on A to bring about B. Recent research shows that children as young as 19 to 24 months of age can quickly learn causal properties of objects from patterns of statistical contingency and can act on that knowledge to bring about effects (Gopnik, 2012; Gopnik & Wellman, 2012; Sobel & Kirkham, 2006; Meltzoff, Waismeyer & Gopnik, 2012). At 20 months, children can infer the desires of others from sampling patterns (Kushnir, Xu & Wellman, 2010) and at 16 months, they can use contingency information to determine whether an effect was caused by their own actions (Gweon & Schulz, 2011). Other lines of research suggest that infants can infer abstract linguistic structure from statistical data (e.g. Saffran, Newport & Aslin, 1996; Lany & Gomez, 2008). However, little is known about the development of children’s ability to infer higher-order relational causal principles from data. In particular, an effect might be caused by an object property (e.g., red blocks activate a toy) or by a higher-order relationship between properties (e.g. two blocks that are the same, regardless of their color, activate a toy). Inferring higher-order relations is essential for building abstract knowledge (Kemp, Perfors & Tenenbaum, 2007; Dewar & Xu, 2010) and reasoning about concepts that are not tied to perceptual properties. The ability to form generalizations about higher-order relations from limited data allows children to make principled abstractions that go beyond the particular properties they have observed. To investigate this, we used a causal version of Premack’s (1983) match-to-sample task. In this task, animals observe an abstract relational pattern – AA’, BB’, and CC’ all lead to a reward. Then they are given a choice between AB (object match) and DD’ (relational match). Although A and B have each individually been associated with the reward, an animal who has inferred the more abstract relational pattern (“same”) should choose DD’. Premack found that chimpanzees could not solve this relational task without hundreds of trials (Premack, 1988) or explicit training to use linguistic symbols for “same” (Premack, 1983; Premack & Premack, 1983; 2002). Additional comparative studies have confirmed this pattern for non-human primates and other animals (Penn, Holyoak, & Povinelli, 2008). These observations have led some researchers to conclude that abstract relational reasoning may be uniquely human. Research examining the origins of relational reasoning using looking-time measures suggests that human infants, like primates, may be able to recognize relational patterns of data (Dewar & Xu, 2010; Tyrell, Stauffer & Snowman, 1991; Ferry, Hespos & Gentner, 2012). However, there is no evidence that infants can use those patterns to make causal inferences or guide actions. In fact, earlier studies have concluded that even preschoolers have difficulty with relational tasks (Christie & Gentner, 2010; Gentner, 2010). Not unlike chimpanzees, children succeeded only when given linguistic coaching to point out the pattern of similarity between two simultaneously presented cases. Even when explicitly instructed to compare objects, 3-year- olds’ performance on these relational tasks was rather tenuous, dropping significantly below chance when the test items were presented sequentially, rather than simultaneously (Christie & Gentner, 2010). This might lead to the conclusion that, even in humans, learning higher- order relations and using them to guide actions is a relatively late-developing ability, which depends on direct instruction, language, and cultural scaffolding. However, the striking success of young children on causal tasks suggests that placing these problems in a causal context might enhance performance. For example, recent evidence suggests that by 24 months, toddlers readily learn