Suppose the Machiavellian intelligence hypothesis is right, and the problems created by social complexity were indeed an important spur to increasing intelligence during primate and human evolution. Do we then need to assume that this effect was operating constantly and universally? Not necessarily. It is perfectly possible that intellectual capacity was increased at several different points in the ancestral line leading to humans, and that these events were caused by evolutionary responses to quite different circumstances. And what of non-primates? Are all signs of specialisation in extra brain capacity to be explained in the same way? Clearly this is rather unlikely.

The question is, which particular observed facts does the Machiavellian intelligence hypothesis explain, if any? On a rather grand interpretation, as perhaps suggested by ‘Social Expertise and the Evolution of Intellect in Monkeys, Apes and Humans’ (the subtitle of Machiavellian Intelligence, Byrne & Whiten, 1988), the need to handle social complexity would be the stimulus to all intellectual advances throughout the evolutionary ancestry of humans and primates. On the most narrow interpretation, the hypothesis would assert only that social complexity lies behind certain specific differences in ability between the haplorhine and strepsirhine primate groups. This more modest claim is already strongly supported by current evidence. What we must do, is first locate the evolutionary events that contributed to the eventual pre-eminence of human intellect. Only then can we tentatively assign causes, in the form of selective pressures that promoted change.

Introduction

The social intelligence hypothesis posits that the large brains and distinctive cognitive abilities of primates (in particular, anthropoid primates) evolved via a spiralling arms race in which social competitors developed increasingly sophisticated ‘Machiavellian’ strategies (Byrne & Whiten, 1988). The idea stemmed originally from observations suggesting that the polyadic interactions and relationships typical of anthropoid societies place exceptional demands on the ability of individuals to process and integrate social information. This hypothesis has been contrasted with foraging niche hypotheses, which propose that it is the need to find food in patchy, unpredictable environments, or even to extract it from awkward substrates, that required large brains and cognitive specialisation (e.g. Gibson, 1986; Milton, 1988). A major task in the study of primate cognition is to devise tests of these hypotheses.

In trying to establish the nature of cognitive adaptation, studies of the behaviour of individual species (whether experimental or based on field observations) are inevitably of limited value. While such studies may suggest what cognitive skills are used in meeting the demands of a particular lifestyle (e.g. Milton, 1988; Cheney & Seyfarth, 1990; Chapter 8), they do not in themselves provide tests of the evolutionary hypotheses. Indeed, they occasionally lead to the circular logic that primate species are good at the things that primatologists have chosen to study (such as complex sociality, or difficult foraging). This problem may also be compounded by ‘primatocentric’ reasoning, in which primate behaviour is automatically assumed to be more complex and clever, and more demanding of evolutionary explanation, than is non-primate behaviour.

Sociality is not limited to primates. Other animals, such as corals and colonial hydrozoans, are far more impressively social in the extent to which individuals co-operate, even forsaking their autonomies, as part of a colonial ‘superorganism’ (Wilson, 1975). To consider the hypothesis that primate intelligence evolved in response to the demands of social life therefore requires us to do more than identify common aspects of sociality in this order: we should identify ways in which primate social systems differ from those of other animals.

All primates are social, but not all are gregarious. Gregarious primates live in groups that typically persist beyond the lifetimes of their individual members. These groups are largely ‘closed’, in that entrance of strangers is resisted. The most distinctive features of primate societies, however, are that their members (a) recognise and interact with one another as individuals (b) over the course of relatively long lifetimes in such a way that (c) earlier interactions influence later ones. Thus every individual is part of a network of individualised social relationships, and each relationship has a unique and potentially long history. Because the occurrence and outcomes of interactions between individuals at one time may influence the occurrence and outcome of their subsequent interactions, the pair's history of interaction becomes one relevant factor in predicting the future course of the relationship by observers and by the animals themselves.

Members of non-human primate groups have social relationships with each of their group-mates, although these relationships vary in form.

Machiavellian Intelligence II is not just a second edition of Machiavellian Intelligence. All but one of the authors are new. The one author in common is writing on a different topic, as are the editors themselves. Moreover, the titles and contents of the chapters are not simple updates of those in the original volume. Instead, this book complements our earlier one in rather particular ways. This means that although we provide an introductory chapter to bring readers new to the area up to speed, the significance of the papers in this new book will be much better appreciated if the contents of its predecessor volume have been assimilated. We trust that serious new students of Machiavellian intelligence will take the time to do this and — although we would say this wouldn't we? – we strongly believe that there is no substitute for this route to a rounded grasp of the subject.

Machiavellian Intelligence brought together the scattered origins of the idea that primate intellect had its roots in the problems posed by complex social life, and additional chapters explored the reasons for its plausibility. Since, then, ‘Machiavellian intelligence’ has become a commonplace phrase in the literature, even to the point of acceptance where it sometimes appears with a small ‘m’! We felt the time was ripe to assess progress.

Machiavellian Intelligence II is designed to move things forward in two main ways, as suggested by our subtitle. One falls mainly under the heading of extensions of the earlier body of empirical work and accompanying theory.

Introduction: Unpredictability, animacy and psychology

Nature cloaks herself in many modes of unpredictability. Science advances in part by recognising and distinguishing these modes (see Kruger et al., 1987). Statistical mechanics modelled the complexity of fluids using stochastic principles. Quantum theory accepted the noisiness of elementary particles. Chaos theory revealed that many dynamical systems show extreme sensitivity to initial conditions. Evolutionary theory showed how random variation plus cumulative selection could yield organic complexity. Such progress in physics and biology has not been matched by psychology. Although unpredictability is a hallmark of animal behaviour, it has been the bane of the behavioural sciences. Variation in behaviour, whether across species, situation, space, or time, has usually been attributed either to adaptation or to error, with adaptation narrowly defined as systematic (if complex) correspondence between environmental conditions and behavioural tactics, and error narrowly defined as raw behavioural noise. Psychology's favourite statistical shibboleth, analysis of variance, assumes that behaviour can be explained by the interaction of environmental determinants and random, non-adaptive noise.

This chapter examines a type of behaviour that is both adaptive and noisy, both functional and unpredictable, and that has therefore been overlooked by most behavioural scientists. The difficulty of predicting animal behaviour may be much more than a side-effect of the complexity of animal brains. Rather, the unpredictability may result from those brains having been selected over evolutionary history to baffle and surprise all of the would-be psychologists who preceded us. To appreciate why psychology is hard, we have to stop thinking of brains as physical systems full of quantum noise and chaos, or as computational systems full of informational noise and software bugs.

Like the first volume of Machiavellian Intelligence this successor is concerned with the role of social intelligence in primate evolution. The editors note ‘three principal branch points’ in primate evolution at which selective pressures for intellectual change need to be identified, of which the Homo line is the last (Chapter 1). The Homo line is characterised by ‘massive brain enlargement, and extensive stone tool use, (see p. 14). My own chapter begins by looking briefly at questions raised by this astonishing trajectory from apes to Homo sapiens sapiens. If Machiavellian social intelligence can be traced from the strepsirhine line to its greater elaboration in apes, was it further refinement of this form of social intelligence by which the apes bootstrapped themselves to fully human intelligence? If so, were there no new characteristics linked to the hominid transition? The editors suggest that this may have occurred as a legacy from ape intelligence, or as a consequence of ‘social bias’ in solving problems of survival in the changing conditions of hominid ecology. Another possibility they note is the ‘specific development of a social module or modules, independent from other modules used for non-social tasks’ (see p. 14).

What form might a ‘social bias’ have taken? How would a ‘social module’ operate? Both would seem to involve some sort of linking of cognitive processes and social interaction. Indeed primate social intelligence can be seen as the progressively effective cognitive mapping of the interdependency of own and others' actions. Here primate cognitive mapping of feeding territories (Milton, 1988) may have been a precurser of the cognitive modelling ofcontingent interaction.

In 1988, Byrne and Whiten coined the phrase Machiavellian intelligence to portray primate intelligence as geared primarily to the sorts of conniving we ascribe to Machiavelli — deceit, cunning, and other manipulative, self-serving tactics — in short, to navigating the social, not the physical world. As they point out in this second edition (Chapter 1), intelligence honed for sociality may employ strategies for gaining social advantage beyond self-serving social manoeuvres, such as exploiting others' expertise. Exploiting expertise has many faces, for many reasons. It can aim at varied targets – expertise itself, such as knowledge or skills, or the products of expertise, especially resources such as food. There are two sides to the story of exploitation, as there are with most social stories – the exploiter's and the exploited's. Exploiters come in many guises, from learners and partners to bullies and thieves. So do the exploited, from co-operative, supportive teachers, sharing partners and tolerant mothers, to unwilling, niggardly hoarders or even neutral, naive dupes; and their responses can affect the nature and success of the ploys exploiters use. All these sides of the story suggest a number of broad factors behind primates' efforts at exploiting others (see Table 7.1). Exploitation may also vary within the primates because of differences in intellectual capacity between primate species, notably between monkeys and great apes. This chapter explores some of the ways in which non-human primates exploit one another's expertise and how various tactical roles come into play when they do.

Exploiting others’ expertise

Exploiting others’ knowledge entails the social transfer of knowledge and skills.

In a ‘protected threat’, a baboon induces a dominant member of its group to attack a third one. The baboon appeases the dominant member whom it uses as a tool to threaten the target and manoeuvres to prevent the target from doing the same (Kummer, 1988). This ‘social tool use’ is mastered by baboons at puberty, whereas chimpanzees are adult before they learn to use a stone as a tool for cracking hard nuts (Boesch & Boesch, 1984). Primates appear to manipulate social objects with more ease and sophistication than physical tools.

Observations such as these have suggested that primate intelligence is designed primarily for the social rather than the physical and have led to the Machiavellian intelligence hypothesis (Whiten & Byrne, 1988a) or social intelligence hypothesis (Kummer et al., 1997). The term Machiavellian intelligence emphasises the besting of rivals for personal gain over co-operation, whereas the term social intelligence (which is the more general term) is neutral on the balance between exploitation and co operation.

The social intelligence hypothesis is both stimulating and vague. It is stimulating because it reminds us that whenever psychologists study intelligence and learning in humans or animals, it is almost invariably about inanimate objects: symbols, sticks and bananas. It is vague because the nature of the intelligence it invokes is largely unclear, and as a consequence, the mechanisms of social intelligence have not yet been specified. This combination of exciting and imprecise should be an alarming signal. The social intelligence hypothesis has the seductive power of a political party with no precise programme that allows everyone unhappy with the established system to project his or her own values on it.

Introduction

In 1988, one section of Machiavellian Intelligence asked ‘are primates mind-readers?’. There seemed an obvious logic for posing the question. One of the most powerful ways to succeed in a complex social world is to read the very minds of one's companions, and get one step ahead in whatever competitive or co-operative games are at stake. We know this most clearly from our own human Machiavellianism, but we also know that the complexities of primate social life suggest niches for the ability and we know that primates have advanced social cognition: thus, the distribution of mindreading mechanisms in the primate order clearly begs investigation. Unfortunately, despite the years that had elapsed since Premack & Woodruff (1978) first tried experimentally to answer the question, ‘Does the chimpanzee have a theory of mind?’ (see Chapter 1), relevant empirical studies were still few in 1988 and mostly restricted to our own species: those on non-human primates could be counted on the fingers of one hand.

The situation has changed dramatically since 1988. Growth in the study of mindreading has blossomed, perhaps more than any other subject dealt with in the predecessor to this volume. To be sure, this has principally focused on the development of the capacity in humans. Developmental psychologists were the first to pick up on the potential of Premack & Woodruff's ideas, and more specifically on suggestions in the peer commentary on the article, that testing whether an individual can discriminate another's false belief would be the most convincing way to demonstrate a true reading of ‘mind’.

The puzzle of egalitarian society

The common ancestor of humans and the African great apes was a nonmonogamous ape, one that lived in a closed social network and exhibited hostile relations between groups with stalking and killing of conspecifics by males. Wrangham (1987) deduced these ancient traits conservatively by tallying behaviours that humans share with all three African apes. However, the presence or absence of social dominance hierarchy was left in abeyance — even though hierarchies are all too apparent in chimpanzees, gorillas, bonobos, and Neolithic and modern humans. The problem, presumably, was that human foragers, being egalitarian, have been taken to exist without any significant hierarchy; this erroneous assumption has seriously confused the assessment of our own political nature.

More recently, Knauft (1991) has likened our political evolution to a ‘U-shaped curve’. He does assume our common ancestor lived hierarchically, but points out that this approach to social life disappeared for a long span of evolutionary time until it returned with chiefdoms, civilisation and modern nations. Focusing on the ‘simple-foragers’ in whose bands evolved the genes we now carry, Knauft characterises them as largely lacking hierarchy in the form of dominance relations or stratification among the males, and as exhibiting little or no leadership and very low levels of inter-group violence.

Recent work of my own (Boehm, 1993) has questioned the first of these assumptions. I have suggested that among foragers hierarchical behaviour did not actually disappear but rather it assumed a radically different form.

Consequences of behaviour and meta-learning, and social intelligence

Don't be too clever in order to be smart

Our title alludes to Clever and Smart, comic figures created by Ibañez, which contrast in the behaviour they use to reach goals. Whereas Clever shows much refinement, Smart acts without many detours, and succeeds as often as Clever. This result would be surprising to common sense or to analysts of social interaction, Machiavellian intelligence and cognitive competence (Handel, 1982; Hinde, 1983; Anderson, 1985). Indeed, the analysis of the cognitive prerequisites of social interaction would normally lead to the conclusion that sophisticatedly planned and performed behaviour is the means to achieve social goals. Yet there is a caveat. The point we want to make is that the consequences of behaviour, not the degree of underlying cognitive complexity, determine social success. Straightforward action—reaction behaviour such as reciprocity (an eye for an eye) may be as efficacious as subtle diplomacy. For example, reciprocity may be well suited to stop overt physical aggression such as a child's temper tantrum. Watzlawick et al. (1967) tell illuminating stories of unsuccessful communication resulting from either endless recursive mindreading or ignorance of quite simple interaction rules (a man who needs a hammer imagines that his neighbour may be unwilling to lend one, and after a lot of thinking on the neighbour's possible motives, knocks angrily at the other's door shouting that he would never accept even a donated hammer). Watzlawick et al. call on interactants to communicate on their communication rules (to meta-communicate) to resolve problems, and like Dennett (1983), think that we can manage only few embedded propositions.

Introduction

In the pain of his passion, Cyrano de Bergerac fed Christian a suite of elegantly crafted lines designed to capture Roxanne's heart. Cyrano's act was clearly deceptive. Christian knew that he was being deceptive, but did not know the basis for Cyrano's apparent act of generosity. And then there is Roxanne, who believes that the handsome Christian is a poetic spirit able to weave verse that strikes at the heart. She is, of course, deceived. Here then, in one triadic interaction, we have Cyrano who knowingly deceives and does so on the basis of his knowledge of what Christian and Roxanne believe and desire. We have Christian who deceives by both withholding information about his lack of eloquence and actively falsifies information by making Roxanne believe that what emerges from his lips are true inspirations from the heart. And Roxanne is our gullible recipient, swept off her feet by Christian's ersatz performance.

Humans perform such complex mental acrobatics all the time, at least those humans who are over the age of about 4 years old and have all of their species-typical neural faculties intact. Is it even reasonable to contemplate the possibility that non-human animals are similarly endowed, to lie, cheat and conceal valuable information from other group members? In this chapter, I wish to accomplish at least three things along the way to answering this question. Firstly, I will discuss several conceptual issues that are relevant to thinking about the origins and subsequent evolution of not only deceptive behaviour, but a mental capacity for deception.

Introduction

Humphrey (1976) suggested that primate information processing skills, as displayed in laboratory learning tasks, exceed the demands of finding food, finding shelter and avoiding danger in the natural habitat, and he hypothesised that the apparent surplus capability evolved in response to the demands posed by life in complex social groups. Other chapters in this book attempt to spell out the empirical predictions of Humphrey's hypothesis, termed the ‘social intelligence’ or ‘Machiavellian intelligence’ hypothesis (Byrne & Whiten, 1988; Cheney & Seyfarth, 1992), and to evaluate the evidence from studies of social behaviour and brain size. In 1976 Humphrey had little information available on how primates find food in their natural habitat, and his statement about the relative simplicity of this task was mainly speculation. An alternative to Humphrey's viewpoint is that primates are capable of learning the relative positions and characteristics of a very large number of objects and topographical features in their natural habitat and that they use this stored information, in combination with current cues, to find food, to discriminate food from non-food objects, and to travel efficiently and safely. In this chapter, the questions of what information primates possess about the structure of their habitat and how such information might contribute to their survival and reproductive success are examined.

To form an evolutionary explanation for as complex a phenomenon as primate learning and memory capabilities requires that the capabilities of interest be well described and that a reasonable guess can be made about their biological value in the animals' evolutionarily relevant environment.

Introduction

The discovery of primate social complexity during the last 20 years stimulated a reinterpretation of the nature and evolution of primate intelligence. In this chapter we attempt to do three things. Firstly we present a short background highlighting some inherent difficulties with the current ‘social complexity/cognition’ model from which the Machiavellian Intelligence hypothesis derives. Next we explore the consequences of these problematic issues with data on sexual consorts in baboons. Finally we present another way to frame the social complexity/cognition link that we feel has the potential to more fully explain our consort data and to resolve some of the inherent ambiguities in the social complexity model of intelligence. In the process we are left to wonder whether Machiavellian intelligence is really ‘Machiavellian’.

The model

The intellectual events that culminated in the Machiavellian Intelligence hypothesis look slightly different from the description offered by Byrne and Whiten (Chapter 1) when seen from the perspective of primate field studies (Strum & Fedigan, 1997). This vantage point may help to explain why the Chance–Jolly–Kummer—Humphrey (Chance & Mead, 1953; Jolly, 1966; Kummer, 1967; Humphrey, 1976) hypotheses about ‘social intelligence’ did not actually begin to constitute a ‘domain’ of knowledge and research for nearly 20 years. Field data and shifts in theoretical orientations were crucial. Long-term studies of chimpanzees (see Goodall, 1986 and references therein) and baboons (Altmann, 1980; Ransom, 1981; Strum, 1981; Stein, 1984), in particular, documented an array of social relationships. These were initially treated as mere ‘social noise‘ resulting from many social animals living together (e.g. Ransom & Ransom, 1971; Ransom, 1981; Goodall 1986).

After a very slow germination in the more than 20 years leading up to 1988, the ‘Machiavellian intelligence hypothesis’ has subsequently been evoked as an explanatory theory in a wide range of contexts: neurophysiology (Brothers, 1990), social anthropology (Goody, 1995), medicine (Crow, 1993) and even news broadcasting (Venables, 1993), in addition to its impact on psychology and studies of primate evolution. All of a sudden, the idea that intelligence began in social manipulation, deceit and cunning co-operation seems to explain everything we had always puzzled about. This popularity may, of course, simply reflect its correctness. However, the vagueness of the theory may also have helped, allowing it to be ‘all things to all men’. The book that brought in the name did not even contain a single, clear definition of the Machiavellian intelligence hypothesis (Byrne & Whiten, 1988a)! This was not simply carelessness, but a reflection of the reality. In many ways, ‘Machiavellian intelligence’ is better seen, not as a precise theory, but as a banner for a cluster of hypotheses that have been under active investigation since before we coined the label.

All these hypotheses share one thing: the implication that possession of the cognitive capability we call ‘intelligence’ is linked with social living and the problems of complexity it can pose. In the mid-1980s, we thought we could discern a rise in the number of studies that acknowledged the potential explanatory power of the hypothesis. However, these were often rather disparate strands: the time, we felt, was ripe for an attempt to orchestrate them into what we hoped would be the beginnings of a more coherent and focused appraisal.