Since the question “Do chimpanzees have a theory of mind?” was raised in 1978, scientists have attempted to answer it, and philosophers have attempted to clarify what the question means and whether it has been, or could be, answered. Mindreading or theory of mind refers to the ability to attribute mental states to other individuals. Some versions of the question focus on whether chimpanzees engage in belief reasoning or can think about false belief, and chimpanzees have been given (...) nonverbal versions of the false belief moved-object task. Other versions of the question focus on whether chimpanzees understand what others can see, and chimpanzees can pass those tests. From this data, some claim that chimpanzees know something about perceptions, but nothing about belief. Others claim that chimpanzees do not understand belief or perceptions, because the data fails to overcome the “logical problem,” and permits an alternative, non-mentalistic interpretation. I will argue that neither view is warranted. Belief reasoning in chimpanzees has focused on examining false belief in a moved object scenario, but has largely ignored other functions of belief. The first part of the paper is an argument for how to best understand belief reasoning and offers suggestion for future investigation. The second part of the paper addresses and diffuses the “logical problem.” I conclude that chimpanzees may reason about belief, but that there is already compelling evidence that they reason about perceptions. (shrink)

on ). Advice about how to move forward on the mindreading debate, particularly when it comes to overcoming the logical problem, is much needed in comparative psychology. In chapter 4 of his book Ockham’s Razors, Elliott Sober takes on the task by suggesting how we might uncover the mechanism that mediates between the environmental stimuli that is visible to all, and chimpanzee social behavior. I argue that Sober's proposed method for deciding between the behaivor-reading and mindreading hypotheses fails given (...) the nature of each of those hypotheses. I argue that the behavior-reading hypothesis that Povinelli and colleagues propose is so rich and robust that it is going to make predictions that are behaviorally indiscernible from the mindreading hypothesis. Further, I argue that the logical problem artificially separates one’s knowledge of behavior and one’s knowledge of mind. If we reject this form of dualism, the logical problem doesn’t arise. (shrink)

An individual has a theory of mind if he imputes mental states to himself and others. A system of inferences of this kind is properly viewed as a theory because such states are not directly observable, and the system can be used to make predictions about the behavior of others. As to the mental states the chimpanzee may infer, consider those inferred by our own species, for example, purpose or intention, as well as knowledge, belief, thinking, doubt, guessing, (...) pretending, liking, and so forth. To determine whether or not the chimpanzee infers states of this kind, we showed an adult chimpanzee a series of videotaped scenes of a human actor struggling with a variety of problems. Some problems were simple, involving inaccessible food as in the original Kohler problems; others were more complex, involving an actor unable to extricate himself from a locked cage, shivering because of a malfunctioning heater, or unable to play a phonograph because it was unplugged. With each videotape the chimpanzee was given several photographs, one a solution to the problem, such as a stick for the inaccessible bananas, a key for the locked up actor, a lit wick for the malfunctioning heater. The chimpanzee's consistent choice of the correct photographs can be understood by assuming that the animal recognized the videotape as representing a problem, understood the actor's purpose, and chose alternatives compatible with that purpose. (shrink)

I respond to an argument presented by Daniel Povinelli and Jennifer Vonk that the current generation of experiments on chimpanzee theory of mind cannot decide whether chimpanzees have the ability to reason about mental states. I argue that Povinelli and Vonk's proposed experiment is subject to their own criticisms and that there should be a more radical shift away from experiments that ask subjects to predict behavior. Further, I argue that Povinelli and Vonk's theoretical commitments should lead them (...) to accept this new approach, and that experiments which offer subjects the opportunity to look for explanations for anomalous behavior should be explored. (shrink)

I respond to an argument presented by Daniel Povinelli and Jennifer Vonk that the current generation of experiments on chimpanzee theory of mind cannot decide whether chimpanzees have the ability to reason about mental states. I argue that Povinelli and Vonk’s proposed experiment is subject to their own criticisms and that there should be a more radical shift away from experiments that ask subjects to predict behavior. Further, I argue that Povinelli and Vonk’s theoretical commitments should lead them (...) to accept this new approach, and that experiments which offer subjects the opportunity to look for explanations for anomalous behavior should be explored. (shrink)

Chimpanzee language studies have generated much heated controversy, as Roger Fouts can attest from firsthand experience. Perhaps this is because language is usually considered to be what truly distinguishes humans from apes. If chimps can indeed be taught the rudiments of language, then the difference between them and us is not as great as we might have thought. It is a matter of degree rather than kind, a continuity, and our species is not so special after all. The advantage (...) of this continuity thesis, as Fouts has emphasized, is that it conforms to the general tenets of evolutionary theory, and fits well with the evidence from paleontology and genetics that suggests that apes and humans are close cousins. It also .. (shrink)

The question of whether chimpanzees, like humans, reason about unobservable mental states remains highly controversial. On one account, chimpanzees are seen as possessing a psychological system for social cognition that represents and reasons about behaviors alone. A competing account allows that the chimpanzee's social cognition system additionally construes the behaviors it represents in terms of mental states. Because the range of behaviors that each of the two systems can generate is not currently known, and because the latter system depends (...) upon the former, determining the presence of this latter system in chimpanzees is a far more difficult task than has been assumed. We call for recognition of this problem, and a shift from experimental paradigms that cannot resolve this question, to ones that might allow researchers to intelligently determine when it is necessary to postulate the presence of a system which reasons about both behavior and mental states. (shrink)

Chimpanzees follow the gaze of conspecifics and humans — follow it past distractors and behind barriers, ‘check back’ with humans when gaze following does not yield interesting sights, use gestures appropriately depending on the visual access of their recipient, and select different pieces of food depending on whether their competitor has visual access to them. Taken together, these findings make a strong case for the hypothesis that chimpanzees have some understanding of what other individuals can and cannot see. However, chimpanzees (...) do not seem nearly so skillful in the Gesture Choice and Object Choice experimental paradigms. Neither behavioral conditioning nor theory of mind explanations can account for these results satisfactorily. Instead this chapter proposes the idea that chimpanzees have the cognitive skills to recall, represent, categorize, and reason about the behavior and perception of others, but not their intentional or mental states, because they do not know that others have such states since they cannot make a link to their own. Human beings began their own evolutionary trajectory with these same skills, but then at some point in their evolution (probably quite recently) they began to understand that their own experience could serve as some kind of model for that of other persons. This allowed for even better prediction and control of the behavior of others and better communication and cooperation with them as well, and so it was an adaptation with immediate adaptive consequences that ensured its survival. (shrink)

I analyze two recent parsimony arguments that have been offered to break the current impasse in the chimpanzee mindreading controversy, the ‘logical problem’ argument from Povinelli, Penn, and Vonk, and Sober's attempt to apply model selection criteria in support of the mindreading hypothesis. I argue that Sober's approach fails to adequately rebut the ‘logical problem’. However, applying model selection criteria to chimpanzees' own mental models of behavior does yield a response to the ‘logical problem’ and reveals an adaptive advantage (...) of mindreading models and a potential solution to a paradox raised by Whiten. (shrink)

Animals react and adjust to the behavior of their conspecifics. Much less is known about whether animals also react and adjust to the psychological states of others. Recent evidence suggests that chimpanzees follow the gaze of others around barriers, past distracters, and check back if they find nothing. Chimpanzees can gauge the motives of a human experimenter and distinguish his intentional from accidental actions. These results suggest that chimpanzees interpret the perceptions and actions of others from a psychological perspective -they (...) seem to know what others can and cannot see and what goals others pursue. It is hypothesized that the co-operation of the ability to operate on psychological states and the motivation to share emotions and experiences with others are key ingredients in the making of human minds. (shrink)

Theories of children's understanding of mind benefit from rigorous interpretations of demonstrations of similar understandings in closely related species. This commentary describes how Carpendale & Lewis's (C&L's) argument could be made more persuasive with a more rigorous interpretation of the studies of chimpanzees' understanding of mind.

From an early age, humans know a surprising amount about basic physical principles, such as gravity, force, mass, and shape. We can see this in the way that young children play, and manipulate objects around them. The same behaviour has long been observed in primates - chimpanzees have been shown to possess a remarkable ability to make and use simple tools. But what does this tell us about their inner mental state - do they therefore share the same understanding to (...) that of a young child? Do they understand the simple, underlying physical principles involved? Though some people would say that they do, this book reports groundbreaking research that questions whether this really is the case. -/- Folk Physics for Apes challenges the assumptions so often made about apes. It offers us a rare glimpse into the workings of another mind, examining how apes perceive and understand the physical world - an understanding that appears to be both similar to, and yet profoundly different from our own. The book will have broad appeal to evolutionary psychologists, developmental psychologists, and those interested in the sub-disciplines of cognitive science (philosophy, anthropology). The book additionally offers for developmental psychologists some valuable new non-verbal techniques for assessing causal understanding in young children. (shrink)

Among the "hard cases" of captive animal research is the continued use of chimpanzees in harmful experimental science. In a recent article I contend that contemporary animal welfare science and chimpanzee behavioral studies permit, if not require, a reappraisal of the moral significance of chimpanzee dissent from participation in certain experiments. In what follows, I outline my earlier argument, provide a brief survey of some central concepts in pediatric research ethics, and use these to enrich an understanding of (...) chimpanzee dissent useful for research ethics. (shrink)

Lurz and Krachun propose a new experimental protocol designed to discriminate genuine mindreading animals from mere behavior-readers and to give evidence in favor of the claim that chimpanzees are capable of attributing internal goals to others. They suggest that chimpanzees' variety of "internal goal attribution" consists in attributing to others basic intentional representations, baptized by Millikan as "pushmi-pullyu representations". Now, Millikan distinguishes what I propose to call 'pure' PPs from more complex varieties of PPs, which allow their owners to respond (...) more flexibly to their environments. But, what would happen if we tried to differentiate, analogously, between more or less sophisticated mind-readers in virtue of the sorts of PPs that they could attribute to others? What would attributing complex PPs consist in and how would such capacity increase the predictive powers of chimpanzee mind-readers? This paper offers an answer to these questions. Based on Millikan's work, I differentiate two varieties of complex PPs. Then, I examine what a basic mind-reader, only capable of attributing 'pure' PPs, would be able to do. After that, I distinguish two more sophisticated varieties of mindreading, each consisting in the attribution of one of the complex PPs previously presented, and I show how the ability to attribute complex PPs to others comes with more potent and flexible capacities to anticipate their behavior. Finally, I offer some reasons to think that attributing complex PPs is still simpler than full-blown mindreading and I briefly evaluate the prospects of extending this proposal to infant social cognition. (shrink)

We argue against theory-of-mind interpretation of recent false-belief experiments with young infants and explore two other interpretations: enactive and behavioral abstraction approaches. We then discuss the differences between these alternatives.

Following Darwin, many comparative psychologists assume that the human mind is a kind of ape mind, differing only in degree from the extant apes – we call this the mental continuity assumption. However, the continuity principle in evolutionary theory does not posit continuity between extant closely related species, but between extant species and their extinct ancestors. Thus, it is possible that some human cognitive capacities have no parallels in extant apes, but that they emerged in extinct hominid species (...) after the human-chimpanzee divergence. Our examination of the case of social cognition from an archaeological and comparative psychological perspective suggests that the human brain is not simply an enlarged chimpanzee brain. Instead, natural selection seems to have favoured a different social cognition in both species. (shrink)

The question, “Does the chimpanzee have a theory of mind?” is logically identical to the question, “Does the chimpanzee have a soul?” It is a peculiarity of our culture that we talk about anyone having a mind, and such talk is unhelpful for a science of behavior. The label “killjoy hypothesis” is an ad hominem attack.

The study of animal cognition raises profound questions about the minds of animals and philosophy of mind itself. Aristotle argued that humans are the only animal to laugh, but in recent experiments rats have also been shown to laugh. In other experiments, dogs have been shown to respond appropriately to over two hundred words in human language. In this introduction to the philosophy of animal minds Kristin Andrews introduces and assesses the essential topics, problems and debates as they cut (...) across animal cognition and philosophy of mind. She addresses the following key topics: what is cognition, and what is it to have a mind? What questions should we ask to determine whether behaviour has a cognitive basis? the science of animal minds explained: ethology, behaviourist psychology, and cognitive ethology rationality in animals animal consciousness: what does research into pain and the emotions reveal? What can empirical evidence about animal behaviour tell us about philosophical theories of consciousness? does animal cognition involve belief and concepts; do animals have a ‘Language of Thought’? animal communication other minds: do animals attribute ‘mindedness’ to other creatures? moral reasoning and ethical behaviour in animals animal cognition and memory. Extensive use of empirical examples and case studies is made throughout the book. These include Cheney and Seyfarth’s ververt monkey research, Thorndike’s cat puzzle boxes, Jensen’s research into humans and chimpanzees and the ultimatum game, Pankseep and Burgdorf’s research on rat laughter, and Clayton and Emery’s research on memory in scrub-jays. Additional features such as chapter summaries, annotated further reading and a glossary make this an indispensable introduction to those teaching philosophy of mind, animal cognition. It will also be an excellent resource for those in fields such as ethology, biology and psychology. (shrink)

In their 1978 paper, psychologists David Premack and Guy Woodruff posed the question, “Does the chimpanzee have a theory of mind?” They treated this question as interchangeable with the inquiry, “Does a chimpanzee make inferences about another individual, in any degree or kind?” Here, we offer an alternative way of thinking about this issue, positing that while chimpanzees may not possess a theory of mind in the strict sense, we ought to think of them as enactive (...) perceivers of practical and social affordances. As such, we reframe the question: “Are chimpanzees socially enactive?”. (shrink)

This chapter compares the social behaviour of human hunter-gatherers with that of the better-studied chimpanzee species, Pan troglodytes, in an attempt to pinpoint the unique features of human social evolution. Although hunter-gatherers and chimpanzees living in central Africa have similar body weights, humans live at much lower population densities due to their greater dependence on predation. Human foraging parties have longer duration than those of chimpanzees, lasting hours rather than minutes, and a higher level of mutual dependence, through the (...) division of labour between men and women ; which is in turn related to pair-bonding, and meat sharing to reduce the risk of individual hunters' failure on any particular day. The band appears to be a uniquely human social unit that resolves the tension between greater dispersion and greater interdependence. (shrink)

Striking similarities across ape gestural repertoires suggest shared phylogenetic origins that likely provided a foundation for the emergence of language. We pilot a novel approach for exploring possible semantic universals across human and nonhuman ape species. In a forced‐choice task, n = 300 participants watched 10 chimpanzee gesture forms performed by a human and chose from responses that paralleled inferred meanings for chimpanzee gestures. Participants agreed on a single meaning for nine gesture forms; in six of these the (...) agreed form‐meaning pair response(s) matched those established for chimpanzees. Such shared understanding suggests apes' (including humans') gesturing shares deep evolutionary origins. (shrink)

I offer an argument for what mental action may be like in nonhuman animals. Action planning is a type of mental action that involves a type of intention. Some intentions are the causal mental antecedents of proximal mental actions, and some intentions are the causal mental antecedents of distal mental actions. The distinction between these two types of “plan-states” is often spelled out in terms of mental content. The prominent view is that while proximal mental actions are caused by mental (...) states with nonconceptual content, distal mental actions are caused by mental states with conceptual content. I argue that, when we are investigating animal cognition, we need a nonconceptual account for the content of intentions involved in mental actions such as action planning: non-immediate intentions. This in order to defend the claim that creatures that lack conceptual capacities are capable of entertaining plan-states, and thus of exercising mental agency in the form of action planning. (shrink)

Comparative psychology, the multidisciplinary study of animal behavior and psychology, confronts the challenge of how to study animals we find cute and easy to anthropomorphize, and animals we find odd and easy to objectify, without letting these biases negatively impact the science. In this Element, Kristin Andrews identifies and critically examines the principles of comparative psychology and shows how they can introduce other biases by objectifying animal subjects and encouraging scientists to remain detached. Andrews outlines the scientific benefits of treating (...) animals as sentient research participants who come from their own social contexts and with whom we will be in relationship. With discussions of science's quest for objectivity, worries about romantic and killjoy theories, and debates about chimpanzee cognition between primatologists who work in the field and those in the lab, Andrews shows how scientists can address the different biases through greater integration of the subdisciplines of comparative psychology. (shrink)

Since the BBS article in which Premack and Woodruff (1978) asked “Does the chimpanzee have a theory of mind?,” it has been repeatedly claimed that there is observational and experimental evidence that apes have mental state concepts, such as “want” and “know.” Unlike research on the development of theory of mind in childhood, however, no substantial progress has been made through this work with nonhuman primates. A survey of empirical studies of imitation, self-recognition, social relationships, deception, role-taking, (...) and perspective-taking suggests that in every case where nonhuman primate behavior has been interpreted as a sign of theory of mind, it could instead have occurred by chance or as a product of nonmentalistic processes such as associative learning or inferences based on nonmental categories. Arguments to the effect that, in spite of this, the theory of mind hypothesis should be accepted because it is more parsimonious than alternatives or because it is supported by convergent evidence are not compelling. Such arguments are based on unsupportable assumptions about the role of parsimony in science and either ignore the requirement that convergent evidence proceed from independent assumptions, or fail to show that it supports the theory of mind hypothesis over nonmentalist alternatives. Progress in research on theory of mind requires experimental procedures that can distinguish the theory of mind hypothesis from nonmentalist alternatives. A procedure that may have this potential is proposed. It uses conditional discrimination training and transfer tests to determine whether chimpanzees have the concept “see.” Commentators are invited to identify flaws in the procedure and to suggest alternatives. Key Words: apes; associative learning; concepts; convergence; deception; evolution of intelligence; folk psychology; imitation; mental state attribution; monkeys; parsimony; perspective-taking; primates; role-taking; self-recognition; social cognition; social intelligence; theory of mind. (shrink)

There is something important about the way human primates use touch in social encounters; for example, consider greetings in airports (hugs vs. handshakes) and the way children push each other in a playground (a quick push to warn, a really hard one when it is serious!). Human primates use touch as a way of conveying a wide range of social information. In this chapter I will argue that one of the best ways of understanding social cognition in non-human primates is (...) through touch. Moreover, I will argue that if we would like to describe the evolutionary history of social cognition, touch is one of the ideal modes to operationalize social interaction across different kinds of primates. (shrink)

Comparative psychology, the multidisciplinary study of animal behavior and psychology, confronts the challenge of how to study animals we find cute and easy to anthropomorphize, and animals we find odd and easy to objectify, without letting these biases negatively impact the science. In this Element, Kristin Andrews identifies and critically examines the principles of comparative psychology and shows how they can introduce other biases by objectifying animal subjects and encouraging scientists to remain detached. Andrews outlines the scientific benefits of treating (...) animals as sentient research participants who come from their own social contexts and with whom we will be in relationship. With discussions of science's quest for objectivity, worries about romantic and killjoy theories, and debates about chimpanzee cognition between primatologists who work in the field and those in the lab, Andrews shows how scientists can address the different biases through greater integration of the subdisciplines of comparative psychology. (shrink)

When a chimpanzee stockpiles rocks as weapons or when a frog sends out mating calls, we might easily assume these animals know their own motivations--that they use the same psychological mechanisms that we do. But as Beyond the Brain indicates, this is a dangerous assumption because animals have different evolutionary trajectories, ecological niches, and physical attributes. How do these differences influence animal thinking and behavior? Removing our human-centered spectacles, Louise Barrett investigates the mind and brain and offers an (...) alternative approach for understanding animal and human cognition. Drawing on examples from animal behavior, comparative psychology, robotics, artificial life, developmental psychology, and cognitive science, Barrett provides remarkable new insights into how animals and humans depend on their bodies and environment--not just their brains--to behave intelligently. Barrett begins with an overview of human cognitive adaptations and how these color our views of other species, brains, and minds. Considering when it is worth having a big brain--or indeed having a brain at all--she investigates exactly what brains are good at. Showing that the brain's evolutionary function guides action in the world, she looks at how physical structure contributes to cognitive processes, and she demonstrates how these processes employ materials and resources in specific environments. Arguing that thinking and behavior constitute a property of the whole organism, not just the brain, Beyond the Brain illustrates how the body, brain, and cognition are tied to the wider world. (shrink)

False belief tasks have enjoyed a monopoly in the research on children’s development of a theory of mind. They have been granted this status because they promise to deliver an unambiguous assessment of children’s understanding of the representational nature of mental states. Their poor cousins, true belief tasks, have been relegated to occasional service as control tasks. That this is their only role has been due to the universal assumption that correct answers on true belief tasks are inherently ambiguous (...) regarding the level of the child’s understanding of mental states. It has also been due to the universal assumption that nothing in the child’s developing theory of mind would lead to systematically incorrect answers on true belief tasks. We review new findings that 4- and 5-year-olds do err, systematically and profoundly, on the true belief versions of all the extant belief tasks. This reveals an intermediate level of understanding in the development of children’s theory of mind. Researchers have been unaware of this intermediate level because it produces correct answers in false belief tasks. A simple two-task battery—one true belief task and one false belief task—is sufficient to remove the ambiguity from each task. The new findings show that children do not acquire an understanding of beliefs, and hence a representational theory of mind, until after 6 years of age, or 2 years later than most developmental psychologists have concluded. This raises the question of how to interpret other new findings that infants are able to pass false belief tasks. We review these new infant studies, as well as recent studies on chimpanzees, in light of older children’s failure on true belief tasks, and end with some speculation about how all of these new findings might be reconciled. (shrink)

It is now over twenty years since Premack and Woodruff posed the question, ‘Does the chimpanzee have a theory of mind?’—‘by which we meant’, explained Premack in a later reappraisal, ‘does the ape do what humans do: attribute states of mind to the other one, and use these states to predict and explain the behaviour of the other one? For example, does the ape wonder, while looking quizzically at another individual, What does he really want? What does (...) he believe? What are his intentions? '. (shrink)

What could someone represent that would enable her to track, at least within limits, others' perceptions, knowledge states and beliefs including false beliefs? An obvious possibility is that she might represent these very attitudes as such. It is sometimes tacitly or explicitly assumed that this is the only possible answer. However, we argue that several recent discoveries in developmental, cognitive, and comparative psychology indicate the need for other, less obvious possibilities. Our aim is to meet this need by describing the (...) construction of a minimal theory of mind. Minimal theory of mind is rich enough to explain systematic success on tasks held to be acid tests for theory of mind cognition including many false belief tasks. Yet minimal theory of mind does not require representing propositional attitudes, or any other kind of representation, as such. Minimal theory of mind may be what enables those with limited cognitive resources or little conceptual sophistication, such as infants, chimpanzees, scrub-jays and human adults under load, to track others' perceptions, knowledge states and beliefs. (shrink)

Humans are moral creatures. Among all life on Earth, we alone experience rich moral emotions, follow complex rules governing how we treat one another, and engage in moral dialogue. But how did human morality evolve? And can humans become morally evolved? -/- In A Better Ape, Victor Kumar and Richmond Campbell draw on the latest research in the biological and social sciences to explain the key role that morality has played in human evolution. They explore the moral traits that humans (...) share with chimpanzees; how a more complex moral mind enabled Homo sapiens to arise and out-compete other human species; and the place of morality alongside historic revolutions in technology and social organization. Throughout the book, Kumar and Campbell argue that morality co-evolved with intelligence and complex sociality. Morality prevents societal collapse and enables complex knowledge. -/- After unearthing the ancient origins of human morality, Kumar and Campbell use evolutionary theory to deliver profound insights about how to advance moral progress and resist moral regress, such as reducing animal suffering on industrial farms; capitalizing on the recent revolution in gay rights to foster a nascent revolution in transgender rights; opposing intersectional inequality that impacts women and people of color in lower socioeconomic classes; and addressing major problems of global inequality, especially impending crises of injustice caused by anthropogenic climate change. Understanding how we evolved--and how we continue to evolve--can help us become a better ape. (shrink)

The “somatic marker mechanism” (SMM; Damasio 1994) is proposed as the cognitive and neural basis of the theory of mind mechanism. The SMM evolved for evaluating the intentions, dispositions, and relationships of conspecifics; hence, it is adaptive in the social domain. It is predicted that chimpanzees will indeed have theory of mind (ToM) ability, but that this will be socially domain-specific. Domain-general ToM will be found only in primates with abstract, symbolic language (adult humans). Putative ToM tests require (...) revision in the light of these distinctions. (shrink)

Since Darwin, the idea of psychological continuity between humans and other animals has dominated theory and research in investigating the minds of other species. Indeed, the field of comparative psychology was founded on two assumptions. First, it was assumed that introspection could provide humans with reliable knowledge about the causal connection between specific mental states and specific behaviors. Second, it was assumed that in those cases in which other species exhibited behaviors similar to our own, similar psychological causes were at (...) work. In this paper, we show how this argument by analogy is flawed with respect to the case of second‐order mental states. As a test case, we focus on the question of how other species conceive of visual attention, and in particular whether chimpanzees interpret seeing as a mentalistic event involving internal states of perception, attention, and belief. We conclude that chimpanzees do not reason about seeing in this manner, and indeed, there is considerable reason to suppose that they do not harbor representations of mental states in general. We propose a reinterpretation model in which the majority of the rich social behaviors that humans and other primates share in common emerged long before the human lineage evolved the psychological means of interpreting those behaviors in mentalistic terms. Although humans, chimpanzees, and most other species may be said to possess mental states, humans alone may have evolved a cognitive specialization for reasoning about such states. (shrink)