To give a fish or to teach how to fish? Children weigh costs and benefits in considering what information to transmit.

To give a fish or to teach how to fish? Children weigh costs and benefits in considering what information to transmit. Hyowon Gweon (hyora@mit.edu) Veronica Chu (verochu@mit.edu) Laura E. Schulz (lschulz@mit.edu) Department of Brain and Cognitive Sciences, MIT Abstract about what is being taught (Bonawitz et al., 2011) and decide which informants provide helpful, reliable information (e.g., Koenig, & Harris, 2005; Sabbagh & Baldwin, 2001; Birch, Vautier, & Bloom, 2008; Gweon, Pelton, Konopka, & Schulz, in press). Studies suggest that certain kinds of interpretive biases in pedagogical contexts are present even in preverbal infants (e.g., Yoon, Johnson, & Csibra, 2008; Futo, Teglas, Csibra, & Gergely, 2010; see Csibra & Gergely, 2009; 2011 for reviews). Although there has been relatively less focus on children’s ability to teach others, some prior work suggest that even very young children can appropriately communicate what they know. For instance, 12-month-olds pointed more often to an object for an adult who was ignorant of the object’s location than for an adult who knew where it was (Liszkowski, Carpenter, & Tomasello, 2008). Furthermore, by age three, children expect that a teacher should teach a skill (e.g., how to sing) to a student who lacks the skill rather than the one who already possesses the skill (Strauss, Ziv, & Stein, 2002), suggesting that children have some understanding of what constitutes good teaching. What has been relatively unexplored in the previous literature is the idea that the cognitive capacities that allow us to be good learners may also make us good at sharing information with others as teachers; just as children rationally infer, as learners, what a teacher is trying to communicate, they might be able to tailor the information they provide as teachers with respect to what the learner knows and what she wants to know. However, as an informant, knowing what information to provide is not a trivial problem. In many pedagogical interactions, explicit requests for information are either absent, or ambiguous with respect to what the learner wants to know. Imagine a toddler pointing to a light-up toy and asking, “What is that?” Even such explicit requests are rather ill posed, as the informant could generate various behaviors depending on exactly what the learner wants to know: the toddler might want the toy, might want to know the name of the toy, see its cool effects, understand how the effect is generated, etc. Depending on what the child wants, an effective teacher might simply give the toy to the child, label the toy, show its effects by activating the toy, or explain that pressing a hidden button on the toy causes it to light up. Even when the informant is helpful and knowledgeable about the world, the space of possible sets of data she could provide is virtually unlimited. Previous developmental research on pedagogy has focused on children’s inferences as learners. Here we look at children’s inferences as teachers. We explore the hypothesis that young children consider the goal of the learner and rationally provide evidence that is both informative and cost-efficient. Given a toy with an ambiguous causal structure, children selectively performed costly actions to provide disambiguating evidence only when the learner wanted to know how the toy worked; when the learner only wanted to see the toy’s effects, children chose less costly actions. These results suggest that children flexibly modify their behaviors as teachers by considering what learners need to know. Keywords: cognitive development, pedagogy, social learning, causal learning, pragmatics Introduction We constantly communicate with others, learning from them and sharing what we know. A particularly powerful form of communication occurs when one person clearly knows something about the world and wants to share her knowledge, and another person clearly wants to learn what she knows. In a pedagogical context, an informant provides information to a learner to help her learn about the world, and the learner updates her beliefs given information from the informant. As in any other form of communication, pedagogy is often more than a simple, unidirectional transfer of information. The learner might expect the informant to provide helpful information, and the informant might have a strong motivation to conform to the learner’s expectation. Computational models of pedagogical learning have formalized this idea as a set of inferences that mutually constrain one another; a knowledgeable, helpful informant selects data that increase the learner’s belief in the correct hypothesis, and an ideal learner rationally updates her belief given data from the informant, with the assumption that the data were selected by a helpful, knowledgeable informant (Shafto, Goodman, & Frank, 2012; Shafto, Goodman, & Griffiths, 2014). This suggests that just as the learner considers the informant’s knowledge and intent in pedagogical interactions, the informant also considers what the learner wants in order to select the set of information requisite to her expectations. Prior developmental work has shown children’s receptivity to pedagogically transmitted information.. When learning from a teacher, children draw rational inferences