Abstract: It is widely believed that what distinguishes the social cognition of humans from that of other animals is the belief-desire psychology of four-year-old children and adults (so-called theory of mind). We argue here that this is actually the second ontogenetic step in uniquely human social cognition. The first step is one year old children’s understanding of persons as intentional agents, which enables skills of cultural learning and shared intentionality. This initial step is ‘the real thing ’ in the sense that it enables young children to participate in cultural activities using shared, perspectival symbols with a conventional/normative/reflective dimension—for example, linguistic communication and pretend play—thus inaugurating children’s understanding of things mental. Understanding beliefs and participating in collective intentionality at four years of age—enabling the comprehension of such things as money and marriage—results from several years of engagement with other persons in perspective-shifting and reflective discourse containing propositional attitude constructions. By all appearances, the cognitive skills of human beings are very different from those of other animal species, including our nearest primate relatives. Human

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At first glance, birds and non-human primates (hereafter primates) seem very different. Birds have beaks, feathers, produce offspring that gestate in shells, and can fly. Primates are covered in hair, have forward facing eyes and grasping hands, and while some are arboreal, none of them can fly. Although there

Abstract In a laboratory experiment, we use a public goods game to examine the hypothesis that human subjects use an involuntary eye-detector mechanism for evaluating the level of privacy. Half of our subjects are “watched ” by images of a robot presented on their computer screen. The robot—named Kismet and invented at MIT—is constructed from objects that are obviously not human with the exception of its eyes. In our experiment, Kismet produces a significant difference in behavior that is not consistent with existing economic models of preferences, either self- or other-regarding. Subjects who are “watched ” by Kismet contribute 29 % more to the public good than do subjects in the same setting without Kismet.

For social species like our own, evolutionary success requires more than the basics of finding some food and a mate. In order to survive and reproduce, humans must successfully navigate a rather complicated social world. Each day, we are required to interact with countless other humans, all behaving in ways that we must predict, interpret, and in some cases manipulate. It’s a daunting task, even for large-brained primates like us. Luckily for each of our genetic legacies, we’re pretty good at it. We owe this social sophistication in large part to a remarkable cognitive shortcut—the capacity to think about behaviors in terms of mental states like intentions, desires, thoughts and beliefs, an ability commonly referred to as a theory of mind. The term “theory of mind,” originally coined by Premack and Woodruff (1978), serves as a somewhat literal portrayal of why this cognitive shortcut is considered so remarkable. As Premack and Woodruff (1978) originally noted, our theory of mind is theory-like in that it is a set of inferences about things that are not directly observable—namely, states of the mind—that are then used to make predictions about an individual’s future behaviors. That we, as human adults, have developed a theory about something we cannot directly observe is a fascinating computational feat.

On the 30th anniversary of Premack and Woodruff’s seminal paper asking whether chimpanzees have a theory of mind, we review recent evidence that suggests in many respects they do, whereas in other respects they might not. Specifically, there is solid evidence from several different experimental paradigms that chimpanzees understand the goals and intentions of others, as well as the perception and knowledge of others. Nevertheless, despite several seemingly valid attempts, there is currently no evidence that chimpanzees understand false beliefs. Our conclusion for the moment is, thus, that chimpanzees understand others in terms of a perception–goal psychology, as opposed to a full-fledged, human-like belief–desire psychology.

Homo sapiens possess a unique behavioural system for social action and response, namely, language. Language permits action at a distance by transmitting messages with specific meanings from one individual’s mind to that of another. It is a peculiar system as compared with other structures in the environment, because the information in language that specifies meaning is rather abstract and arbitrary. Despite—or perhaps due to—these characteristics, language is the prime medium for ‘cultural ratcheting ’ (Tomasello, 1999) among humans. In cultural ratcheting, behavioural innovations (e.g. tools) spread through a group and are sustained and elaborated upon across generations. For a group to maintain a system of linguistic behaviours, each individual must be able to learn and adapt to the prevailing information structure. Typically, most of the structure of language is learned within a few years of birth, when the human infants are dependent on and in near-constant contact with caregivers. One account for this is genetic determinism: the structure of the human genome makes the acquisition and use of language inevitable. However, there is ample evidence, too complex to summarize here, that nativist views of language development (e.g. the Chomskian ‘Language acquisition device, ’ poverty-of-the-stimulus claims, and mass-media reports of a so-called “language gene”) are either inadequate or blatantly incorrect (see, e.g. Elman et al., 1996; Pullum & Scholz, 2002). There is no doubt that some species-specific products and processes of the human genome are necessary for human language learning; however, these products are not sufficient to explain early language development (MacWhinney, 1999). Most developmental scientists agree that a more complete account of human language must carefully consider infant’s social experience. Somehow the structure of social information acquired by