August 4, 2010

The Social Brain Hypothesis

Posted in Language and Myth tagged at 4:35 pm by Jeremy

Here’s the fourth section of the Chapter 2 draft of my book, Finding the Li: Towards a Democracy of Consciousness. This section discusses the “social brain” hypothesis that our unique cognitive capabilities came about from dealing with the social complexity of our lives.  All constructive comments from readers of my blog are greatly appreciated.


The Social Brain Hypothesis

Around the same time that Premack and Woodruff were coining the phrase “theory of mind,” a series of ground-breaking studies were forming the idea that primate intelligence “evolved not to solve physical problems, but to process and use social information, such as who is allied with whom and who is related to whom, and to use this information for deception.”[1] In the context of what we learned about Ardi’s circumstances 4.4. million years ago, this certainly makes sense.  Venturing out on the savannah, hominids couldn’t defend themselves alone against hungry carnivores and banded together for safety.  As they did so, they faced ever-increasing cognitive demands from being in bigger social groups.  And it wasn’t just the size of the group, but the complexity of the lifestyle that increased.  If you went out with your buddies on a foraging group, how could you make sure that no-one who remained behind would make a pass at your partner?

Humans and other primates share a Machiavellian intelligence

Decades of research on this subject have, in fact, shown that species of monkeys and apes that typically live in larger groups also have a larger neocortex (the more recently evolved part of the brain that houses the pfc).[2] Even outside of primates, this correlation seems to exist.  A recent study of hyenas, for example, shows that the spotted hyena, which lives in more complex societies, has “far and away the largest frontal cortex” of all the different hyena species.[3] For this reason, experts in the field are comfortable stating that “the balance of evidence now clearly favors the suggestion that it was the computational demands of living in large, complex societies that selected for large brains.”[4]

In the early days of the social brain hypothesis, the emphasis was on the competitive aspect of living in complex societies.  Researchers would talk about “primate politics” and the name of one book on the subject was Machiavellian Intelligence: Social Evolution in Monkeys, Apes and Humans.[5] In the view of an influential thinker on the subject, Richard Alexander, as hominids became more dominant in their ecology, they no longer needed to evolve better capabilities to deal with the natural environment.  Instead, they began to evolve new cognitive skills in order to outcompete each other.  In this way, we became (in his words) our own “hostile force of nature,” entering into a “social arms race” with each other.[6] Alexander saw our ancestors as playing a “mental chess game” with the other members of their group, “predicting future moves of a social competitor… and appropriate countermoves”:

In this situation, the stage is set for a form of runaway selection, whereby the more cognitively, socially, and behaviorally sophisticated individuals are able to out maneuver and manipulate other individuals to gain control of resources in the local ecology and to gain control of the behavior of other people…[7]

Outmaneuvering, manipulation and control… are these then the defining characteristics of our human uniqueness?  If it sounds bleak, it falls well within a tradition that has interpreted Darwin’s original theory of evolution from the same chilling perspective.  As described by some supporters of Alexander’s theory:

The conceptualization of natural selection as a ‘struggle for existence’ of Darwin and Wallace becomes, in addition, a special kind of struggle with other human beings for control of the resources that support life and allow one to reproduce.[8]

While Alexander was honing his theory of the “social arms race,” another biologist, Robert Trivers, was explaining how, from an evolutionary perspective, altruism was really just a sophisticated form of selfishness.  In a much cited paper, he described what he called “reciprocal altruism” as an ancient evolutionary strategy that could be seen in the behavior of fish and birds, and he interpreted human altruism in the same way.  “Under certain circumstances,” he wrote, “natural selection favors these altruistic behaviors because in the long run they benefit the organism performing them.”[9]

This approach is fully consistent with what’s become generally known as the “selfish gene” interpretation of evolution, as popularized by biologist Richard Dawkins.  In this view (which is extensively critiqued later in this book) all evolution can be explained by the “selfish” drive of our genes to replicate themselves.  And those special human characteristics that we value so highly are no exception.  “Let us try to teach generosity and altruism,” Dawkins suggests, “because we are born selfish.”  Alexander himself comes to a similar conclusion, proposing that “ethics, morality, human conduct, and the human psyche are to be understood only if societies are seen as collections of individuals seeking their own self-interest.”[10]

Tomasello emphasizes "shared intentionality" over social competition

However, in recent years, there’s been an important shift in our understanding of these social dynamics.  What has come to seem more remarkable to researchers is not how our bigger brains made us socially competitive, but how they made us more cooperative with each other.  In fact, Tomasello sees this as the key differentiating factor between the social intelligence of humans and that of other primates.  According to him, it’s the chimpanzees, not the humans, who are obsessed with competing against each other.  “Among primates,” he writes, “humans are by far the most cooperative species, in just about any way this appellation is used.”[11] For this reason, Tomasello argues, the “social competition” view may have driven the evolution of primate intelligence, but the cognitive skills that have enabled humans alone to develop language, culture and civilization have been “driven by, or even constituted by, social cooperation.”

Tomasello and his colleague, Henrike Moll, focus on a uniquely human dynamic that they call “shared intentionality,”  which is our ability to realize that another person is seeing the same thing we’re seeing, but that they’re also seeing it from a different perspective.  “The notion of perspective – we are experiencing the same thing, but potentially differently — is,” Moll and Tomasello believe, “unique to humans and of fundamental cognitive importance.”  In their view, it was the special cooperation arising from shared intentionality that “transformed human cognition from a mainly individual enterprise into a mainly collective cultural enterprise involving shared beliefs and practices.”[12]

The idea that we humans evolved a sense of true altruism, where we’re driven to cooperate with our social group by a natural disposition that transcends our selfish needs, may be attractive to some, but it has been shown to have one fundamental flaw: the free-rider problem.  Let’s go back to the Ardi example of the band of males venturing out on a multi-day mission into the savannah looking for meat.  If one of those males secretly sneaks back to camp and makes out with the females still there, then his genes will be the ones that survive.  Evolutionary researchers have, in fact, modeled this problem using game theory and tested real examples in the lab using the famous “prisoner’s dilemma” game[13]*, and have confirmed that only “a few selfish players suffice to undermine the cooperation” of those who trusted each other.[14]

Does this mean that Alexander and company were right, and in fact human social intelligence must be explained by selfish competition?  Not so fast.  Those same researchers have spent years modeling more realistic versions of what life may have been like for early hominids evolving their social skills, and have arrived at a more sophisticated view of innate human cooperation that they have called “altruistic punishment.”


[1] Emery, N. J., and Clayton, N. S. (2004). “The Mentality of Crows: Convergent Evolution of Intelligence in Corvids and Apes.” Science, 306, 1903-1907.

[2] Dunbar, R. I. M., and Shultz, S. (2007). “Evolution in the Social Brain.” Science, 317(7 September 2007).

[3] Zimmer, C. (2008). “Sociable, and Smart” The New York Times, (March 4, 2008).

[4] Dunbar and Shultz, op. cit.

[5] Cited by Moll, H., and Tomasello, M. (2007). “Cooperation and human cognition: the Vygotskian intelligence hypothesis.” Phil. Trans. R. Soc. Lond. B, 362(1480), 639-648.

[6] Cited by Flinn et al., op. cit.

[7] Ibid.

[8] Ibid.

[9] Trivers, R. L. (1971). “The Evolution of Reciprocal Altruism.” The Quarterly Review of Biology, 46(1), 35-57.

[10] Quoted in Gintis, H., Bowles, S., Boyd, R., and Fehr, E. (2003). “Explaining altruistic behavior in humans.” Evolution and Human Behavior, 24(3), 153-172.

[11] Moll and Tomasello, op. cit.

[12] Ibid.

[13] The prisoner’s dilemma game is a fundamental problem in game theory, where if two people cooperate they both gain a high payoff; but if one player betrays the other who is still cooperating, the betrayer wins everything and the cooperator nothing; if both betray each other, they both get a low payoff.

[14] Fehr, E., and Fischbacher, U. (2003). “The nature of human altruism.” Nature, 425, 785-791.


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