We propose that humans are adapted to transfer knowledge to, and receive knowledge from, conspecifics by teaching. This adaptation, which we call 'pedagogy', involves the emergence of a special communication system that does not presuppose either language or high-level theory of mind, but could itself provide a basis facilitating the development of these human-specific abilities both in phylogenetic and ontogenetic terms. We speculate that tool manufacturing and mediated tool use made the evolution of such a new social learning mechanism necessary. However, the main body of evidence supporting this hypothesis comes from developmental psychology. We argue that many central phenomena of human infant social cognition that may seem puzzling in the light of their standard functional explanation can be more coherently and plausibly interpreted as reflecting the adaptations to receive knowledge from social partners through teaching.

osefully and those that are portrayed as accidental. Fourteen-month-olds are less likely to imitate accidental behaviors than purposeful ones (Carpenter, Akhtar, & Tomasello, 1998), 18-month-olds are able to infer the intended action of an actor who fails to # Amanda L. Woodward, Department of Psychology, 5848 South University Avenue, University of Chicago, Chicago, IL 60637; e-mail: ALW1@ccp.uchicago.edu. INFANT BEHAVIOR & DEVELOPMENT 22 (2), 1999, 145--160 ISSN 0163-6383 Copyright 1999 Elsevier Science Inc. All rights of reproduction in any form reserved. achieve it (Meltzoff, 1995), and 24-montholds interpret new verbs as naming purposeful behaviors, rather than accidental ones (Tomasello & Barton, 1994). These findings indicate that by the end of infancy, babies pay attention to the fine details of action, using them to inform their inferences about the actor's goals. The two studies reported here investigate the precursors to this ability in the first year of life. They test whet

Four studies investigated whether and when infants connect information about an actor's affect and perception to their action. Arguably, this may be a crucial way in which infants come to recognize the intentional behaviors of others. In Study 1 an actor grasped one of two objects in a situation where cues from the actor's gaze and expression could serve to determine which object would be grasped, specifically the actor first looked at and emoted positively about one object but not the other. Twelve-month-olds, but not 8-month-olds, recognized that the actor was likely to grasp the object which she had visually regarded with positive affect. Studies 2, 3, and 4 replicated the main finding from Study 1 with 12- and 14-month-olds and included several contrasting conditions and controls. These studies provide evidence that the ability to use information about an adult's direction of gaze and emotional expression to predict action is both present, and developing at the end of the first year of life. q 2002 Elsevier Science B.V. All rights reserved.

University Press

ABSTRACT—One of the most distinctive characteristics of humans is the capacity to learn from what other people tell them. Often new information is provided about an entity that is not present, requiring incorporation of that information into one’s mental representation of the absent object. Here we present evidence regarding the emergence of this vital ability. Nineteen- and 22-month-old infants first learned a name for a toy and later were told that the toy had undergone a change in state (it had become wet) while out of view. The 22-month-olds (but not the 19-month-olds) subsequently identified the toy solely on the basis of the property that they were told about but had never seen. Thus, before the end of their 2nd year, infants can use verbal information to update their representation of an absent object. This developmental advance inaugurates a uniquely human and immensely powerful form of learning about the world. Human knowledge is based on a combination of direct and indirect experience. A large proportion of people’s knowledge comes indirectly—much of it from another person telling them something new, what Harris (2002) refers to as testimony. Sometimes, testimony informs people about objects or events that are present and directly perceivable (e.g., ‘‘Look at that dog. Its paws are all muddy!’’). Often, however, the subject of the information is absent at the time one hears it (e.g., ‘‘Matt’s mom gave him his first haircut, and it looks terrible.’’). The new information can enter one’s knowledge base because the mental representation of the subject one hears about is activated and then updated by this communication. The ability to learn through indirect experience rests on the capacity to understand references to absent entities and events (Hockett, 1960). Although nonhuman animals may share this ability to limited degrees (e.g., monkeys may be informed of the presence of unseen predators by other animals ’ communicative

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Many theories of early word learning begin with the uncertainty inherent to learning a word from its co-occurrence with a visual scene. However, the relevant visual scene for infant word learning is neither from the adult theorist’s view nor the mature partner’s view, but is rather from the learner’s personal view. Here we show that when 18-month old infants interacted with objects in play with their parents, they created moments in which a single object was visually dominant. If parents named the object during these moments of bottom-up selectivity, later forced-choice tests showed that infants learned the name, but did not when naming occurred during a less visually selective moment. The momentary visual input for parents and toddlers was captured via head cameras placed low on each participant’s forehead as parents played with and named objects for their infant. Frame-by-frame analyses of the head camera images at and around naming moments were conducted to determine the visual properties at input that were associated with learning. The analyses indicated that learning occurred when bottom-up visual information was clean and uncluttered. The sensory-motor behaviors of infants and parents were also analyzed to determine how their actions on the objects may have created these optimal visual moments for learning. The results are discussed with respect to early word learning, embodied attention, and the social role of parents in early word learning. 2 Infants learn their first words through the co-occurrence of a heard word and a visual