Why does explaining help learning? Insight from an explanation impairment effect

Why does explaining help learning? Insight from an explanation impairment effect Joseph Jay Williams (joseph_williams@berkeley.edu) Tania Lombrozo (lombrozo@berkeley.edu) Department of Psychology, University of California, Berkeley Bob Rehder (bob.rehder@nyu.edu) Department of Psychology, New York University Abstract Engaging in explanation, even to oneself, can enhance learning. What underlies this effect? Williams & Lombrozo (in press) propose that explanation exerts subsumptive constraints on processing, driving learners to discover underlying patterns. A category-learning experiment demonstrates that explanation can enhance or impair learning depending on whether these constraints match the structure of the material being learned. Explaining can help learning when reliable patterns are present, but actually impairs learning when patterns are misleading. This explanation impairment effect is predicted by the subsumptive constraints account, but challenges alternative hypotheses according to which explaining helps learning by increasing task engagement through motivation, attention, or processing time. The findings have both theoretical and practical implications for learning and education. Keywords: explanation; self-explanation; learning; constraints; impairment; category learning Most teachers and tutors have had the experience of explaining a concept to another person and achieving greater understanding as a result. How does engaging in explanation generate this beneficial effect? This question’s importance is underscored by the ubiquity of the phenomenon, and by converging evidence from cognitive science, education, and cognitive development confirming that explanation plays a significant role in learning. Explanations have been implicated in theories of how conceptual knowledge is represented and how categories are learned (Carey, 1985; Gopnik & Meltzoff, 1997; Murphy & Medin, 1985). Education researchers have demonstrated that explaining has a potent effect on students’ learning and fosters deep understanding that allows generalization to novel contexts (Chi et al, 1989; Chi et al, 1994). Research in cognitive development reveals even more profound effects (Wellman & Liu, 2006; Wellman, in press). Prompting children to explain can accelerate conceptual change, such as developing an understanding of number conservation (Siegler, 2002) and false belief (Amsterlaw & Wellman, Many extant accounts of explanation’s effects have emphasized the metacognitive benefits of explanation, such as prompting learners to identify and fill gaps in their knowledge (Chi et al, 1994; Chi, 2000). Explanations may also focus learners on uncovering the causes that underlie observed outcomes (Wellman & Liu, 2006), or may enhance learning by increasing task engagement in the form of additional motivation, attention, or processing time (for discussion see Siegler, 2002). Williams and Lombrozo (in press) propose and find empirical support for the subsumptive constraints account, according to which explaining exerts constraints on processing that drive people to interpret what they are learning in terms of underlying patterns and regularities. The account is motivated in part by “subsumption” and “unification” theories of explanation from philosophy (Friedman, 1974; Kitcher, 1981), which propose that good explanations show how what is being explained is an instance of a unifying pattern: explanations cite generalizations that subsume what is being explained. If the explanations learners generate must satisfy this constraint, explaining will drive learners to reason and construct beliefs in the service of identifying patterns. When useful regularities exist, the subsumptive constraints account predicts positive effects of explanation through the discovery of generalizations. However, this account also predicts that seeking explanations can impair learning if there is a mismatch between the subsumptive constraints and the material being learned—for example, in situations in which patterns are nonexistent or misleading. This paper tests the prediction that such an explanation impairment effect exists. Investigating the conditions under which explanation hurts learning can inform theories which aim to specify the mechanisms by which explanation helps learning, analogous to the study of visual illusions in perception. The conditions under which human perception or cognition succeeds can be less informative than those under which it breaks down and produces errors because the latter serve as a window onto the cognitive machinery underlying perception, in the case of visual illusions, or cognition, in the case of explanation and learning. In fact, examining explanation’s detrimental effects can discriminate the subsumptive constraints account from current theories, which to date have not predicted explanation impairment effects. In particular, a task engagement account advocates that engaging in explanation leads learners to be more engaged with the learning task, through increased motivation, attention, or time, which should benefit learning in virtually all contexts. The task engagement account provides an intuitive explanation for the beneficial effects of explaining, positing mechanisms that extend to contexts beyond explanation. Some studies argue that explanation has effects that go beyond task engagement, showing that its effects surpass