Savanna-IQ interaction hypothesis

Overview

The basic contention of the Savanna-IQ interaction hypothesis is that intelligent individuals tend to flourish on tasks that are novel--tasks that diverge considerably from the activities that humans have undertaken throughout their evolutionary history (Kanazawa, 2004, 2008; Kanazawa & Perina, 2009). This contention emerges from two key premises.

According to the first premise, derived from the field of evolutionary psychology, the human brain primarily evolved to accommodate the conditions that were pervasive during a previous epoch (e.g., Cosmides, 1989; Cosmides & Tooby, 1989; Crawford, 1993; Tooby & Cosmides, 1990; Tooby, Cosmides, & Price, 2006). Many cognitive mechanisms evolved to facilitate key tasks at the time, such as foraging (Rode, Cosmides, Hell, & Tooby, 1999). As a consequence, the human brain may not be optimal to withstand the complexities of society today.

Specifically, the human brain primarily evolved while humans negotiated the African savanna, during the Pleistocene Epoch. To clarify, geological time tends to be divided into various units, such as supereons, the largest unit, eons, eras, periods, epochs, and ages, the smallest unit. To illustrate, Triassic, Jurassic, Cretaceous, Paleogene, and Neogene are all periods. The latest period, Neogene, entails the Miocene, Pliocene, Pleistocene, and Holocene epochs. The Pleistocene epoch, which spanned from approximately 2.5 million years ago to 130,000 years ago, witnessed the evolution of man.

According to the second premise, mechanisms evolved that enable humans to solve problems that diverged from the tasks that epitomized the Pleistocene epoch. These mechanisms, collectively, represent general intelligence.

Taken together, these premises imply that general intelligence might not be needed to resolve problems or undertake tasks that mirror the activities that humans completed during the Pleistocene epoch. In contrast, general intelligence does enhance performance on tasks that are touted as evolutionary novel.

Empirical evidence

Nocturnal activities

Several studies have accumulated evidence that substantiate the Savanna-IQ interaction hypothesis. Kanazawa and Perina (2009) contended, and then verified, that intelligent individuals are more inclined to flourish at night. Specifically, humans evolved to be diurnal--to restrict most of their activities to the day rather than to the night.

Many arguments reinforce the proposition that humans, throughout evolution, tend to be active mainly in the day. First, humans rely appreciably on their vision--a sensory modality that is not especially effective at night, particularly before the advent of artificial light. Second, in almost all traditional cultures, as emphasized by a vast array of ethnographies, activity begins at dawn and tends to wane at dusk. This pattern, for example, has been observed in the Yanomano, the Mukogodo, the !Kung San, and the Sacha Runa (for a brief review, see Kanazawa & Perina, 2009).

Accordingly, the modern trend to udnertake some activity in the night, a trend that was facilitated by artificial lighting, demands intelligence. That is, according to the Savanna-IQ interaction hypothesis, general intelligence is needed to complete tasks that diverged from the ubiquitous activities in a previous epoch. General intelligence, therefore, should be correlated with willingness to maintain activity during the night.

To assess this possibility, high school students completed a test of verbal intelligence, the Peabody Picture Vocabulary Test. In addition, participants were asked to estimate the time they usually retire to bed on both school days and weekends. Consistent with the Savanna-IQ interaction hypothesis, students who performed well on the test of verbal intelligence also typically retired to bed late (Kanazawa & Perina, 2009).

Alternative explanations for nocturnal activities

Nevertheless, alternative explanations could, potentially, explain the relationship between general intelligence and activity during the night. Specifically, many other factors affect the circadian preferences of individuals, sometimes called morning versus evening types.

Diaz-Morales (2007), for example, showed that personality is related to whether individuals are alert, energetic, and capable during the morning or night. Specifically, individuals who prefer the night tend to be less conscientious. They also utilize logical rational arguments, in lieu of their intuition, to reach decisions. Finally, they prefer tangible information rather than abstract concepts.

Several mechanisms could explain the association between personality and activity during the night. To illustrate, the body clock of humans naturally spans 24 hours. That is, if humans lived in a cave, with no interaction with anyone else, they would awake 1 hour later each day. As a consequence, all humans experience a natural tendency to want to awake later each morning. Conscientious individuals, however, are especially likely to conform to social conventions. That is, they override their natural impulses more effectively and, as a consequence, can more easily awake earlier.

In short, individuals who are conscientious, and also neglect their intuitions, are more alert in the morning than in the evening. These qualities, however, might hinder intelligence, at least on some tasks (see Cognitive experiential self theory).

References

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Cosmides, L., & Tooby, J. (1989). Evolutionary psychology and the generation of culture, part II. Case study: A computational theory of social exchange. Ethology and Sociobiology, 10, 51-97.

Cosmides, L., & Tooby, J. (1996). Are humans good intuitive statisticians after all? Rethinking some conclusions from the literature on judgment under uncertainty. Cognition, 58, 1-73.

Cosmides, L., & Tooby, J. (2000). Evolutionary psychology and the emotions. In M. Lewis, & J. M. Haviland-Jones (Eds.), Handbook of emotions (pp.91-115). (2nd ed.). NY: Guilford.

Cosmides, L., & Tooby, J. (2005). Neurocognitive adaptations designed for social exchange. In D. M. Buss (Ed.), Handbook of evolutionary psychology (pp. 584-627). Hoboken, NJ: Wiley.

Diaz-Morales, J. F. (2007). Morning and evening-types: Exploring their personality styles. Personality and Individual Differences, 43, 769-778.

Fiddick, L., Cosmides, L., & Tooby, J. (2000). No interpretation without representation: The role of domain-specific representations and inferences in the Wason selection task. Cognition, 77, 1-79.

Kanazawa, S. (1998). A possible solution to the paradox of voter turnout. Journal of Politics, 60, 974-995.

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Kanazawa, S. (2004). General intelligence as a domain-specific adaptation. Psychological Review, 111, 512-523.

Kanazawa, S. (2008). Temperature and evolutionary novelty as forces behind the evolution of general intelligence. Intelligence, 36, 99-108.

Kanazawa, S., & Kovar, J. L. (2004). Why beautiful people are more intelligent. Intelligence, 32, 227-243.

Kanazawa, S., & Perina, K. (2009). Why night owls are more intelligent. Personality and Individual Differences, 47, 685-690.

Klein, S. B., Cosmides, L., Tooby, J., & Chance, S. (2001). Priming exceptions: A test of the scope hypothesis in naturalistic trait judgments. Social Cognition, 19, 443-468.

Klein, S. B., Cosmides, L., Tooby, J., & Chance, S. (2002). Decisions and the evolution of memory: Multiple systems, multiple functions. Psychological Review, 109, 306-329.

Klein, S. B., Rozendal, K., & Cosmides, L. (2002). A social-cognitive neuroscience analysis of the self. Social Cognition, 20, 105-135.

Rode, C., Cosmides, L., Hell, W., & Tooby, J. (1999). When and why do people avoid unknown probabilities in decisions under uncertainty? Testing some predictions from optimal foraging theory. Cognition, 72, 269-304.

Sperber, D., & Girotto, V. (2002). Use or misuse of the selection task? Rejoinder to Fiddick, Cosmides, and Tooby. Cognition, 85, 277-290.

Stone, V. E., Cosmides, L., Tooby, J., Kroll, N., & Knight, R. T. (2002). Selective impairment of reasoning about social exchange in a patient with bilateral limbic system damage. Proceedings of the National Academy of Sciences, 99, 11531-11536.

Tooby, J., Cosmides, L., & Price, M. E. (2006). Cognitive adaptations for n-person exchange: The evolutionary roots of organizational behavior. Managerial and Decision Economics, 27, 103-129.

Created by Dr Simon Moss on 12/10/2009

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