Skoyles's claim that the large brains of modern humans are related to our capacity for developing expertise seems well founded. However, there are other possible candidates for this role. I discuss two of them, problem-solving ability and the ability to gather and remember large amounts of facts.
2. The word "problem" has been defined in different ways by different authors. Mayer's (1990, p. 284) definition contains the essential elements, and should be uncontroversial: "A 'problem' exists when a situation is in a given state, the problem solver wants the situation to be a goal state, and there is no obvious way of transforming the given state into the goal state." In a description that should be equally uncontroversial, Ericsson & Hastie (1994) say that having expertise means having "domain-specific representations and working memory skills that support specialized planning, reasoning, and evaluation." A task is only a problem when there is no obvious way of reaching the goal state. Due to their sophisticated skills, which take years to develop, experts see obvious ways of performing tasks that are problems to other people.
3. It is true that the capacity to develop expertise has obvious survival value, as maintained by Skoyles. It can nevertheless be argued that the ability to solve problems, which is something else, may have at least the same value to a hunter-gatherer. Expertise is for stable environments, but problem solving ability is for adapting to new and unknown circumstances: Communicating with members of another culture, in order to promote co-operation or avoid being harmed; hunting a new kind of animal; finding out how to grow a new type of crop; discovering how to avoid or cure disease -- indeed, dealing with all types of unknown situations, from little things to acute and life-threatening crises. If one has not encountered a certain culture or seen someone suffer from a certain disease before, one may not have much expertise that can be brought to bear on these problems. In addition, experts tend to become victims of mechanization effects that may make them less efficient than non-experts at solving new types of problems (Baron, 1994). Hence, there is little doubt that the ability to solve problems has had survival value.
4. But is not problem solving ability more or less the same as IQ? It does not seem to be. Several studies indicate that the correlation between IQ and the ability to solve problems is low (Dörner, 1986; Helstrup, 1988; Yama, Umemoto, & Kinjo, 1990, but see Raaheim, 1989).
5. No direct evidence appears to exist regarding the relation between brain size and expertise. There is evidence to indicate that problem solving ability may be related to brain size in normal humans, however. First of all, as Skoyles (1999) notes, men have somewhat larger brains than women. Given that men tend to be bigger than women, this is not surprising. However, there seems to be a sex difference in brain weight that does not disappear when body surface area and height is controlled for. For example, Ankney (1992) found a mean difference of 100 g, favoring men, among 168 cm tall whites (the average height for men and women combined in his sample of 1261 American adults) (see also Rushton & Ankney, 1996). Sex hormones seem to play a role: The brains of female rats have been found to grow heavier after ovariectomy, with substantial increase in dendritic arbor and spine density (Stewart & Kolb, 1994). Several studies have found that women do worse than men on creative problem solving tasks (e.g., Kaufmann, 1979; Maier, 1970), as well as on tasks that may be related, such as mathematical reasoning (Stumpf & Jackson, 1994; Kimura, 1993), and spatial problems (Voyer, Voyer, & Bryden, 1995).
6. Solving a problem means mastering a new situation. There are strong indications that developing a capacity for problem solving is related to increased brain weight: Several studies of animals reared in enriched environments, with many opportunities to master new situations through problem solving, show not only clear changes in cortical morphology, but also increases in overall brain weight. Rats, for instance, consistently show brain weight increases in the order of 7% - 10% after 60 days (Kolb & Whishaw, 1998), though some of this increase could result from increased physical activity (cf. Neeper, Gomez-Pinilla, Chol, & Chotman, 1995).
7. It seems, then, that both expertise and problem-solving ability may have played a role in increasing the brain size of humans. However, at least one more candidate needs to be considered: The ability to consciously remember large quantities of facts from a wide variety of areas.
8. Expertise has a limited area of applicability. Leading a hunter-gatherer life in a way that increases one's probability of surviving and spreading one's genes may often call for being a jack of all trades, not just a master of one. To some extent, factual knowledge can make up for the many years of task-specific practice that is a prerequisite of expertise (and no one can have expertise in very many fields). Furthermore, being knowledgeable gives one an opportunity to teach -- thereby forging social bonds and gaining prestige. Knowledge also opens up possibilities for social climbing; and, perhaps most important: To a person with substantial factual knowledge, many potential problems never become problems -- knowledgeable people can draw on what they know: General principles and heuristics, as well as trivia. It should be noted that across several areas, men, who, as we have seen, tend to have bigger brains, ceteris paribus, also tend to know more facts than do women (Dale, Saarinen, & MacCabe, 1995; Halpern, Haviland, & Killian, 1998; Stromsnes, 1995)
9. This brief commentary does not purport to show that the large brain of modern humans has been selected to help us solve problems and remember facts. Nor does it demonstrate that a bigger brain will give individuals an increased problem-solving ability, a greater interest in factual knowledge, or better semantic memory. Furthermore, some of the arguments are based on findings indicating a sex-related difference in the brain size of humans, even after controlling for height and body surface. It should therefore be noted that women seem to excel in fields that may be related to survival. For instance, their verbal skills are typically superior to those of men (e.g., Halpern, 1997), even though their brain weight, other things equal, seems to be somewhat lower. One explanation for this may be the finding that women have slightly more extensive dendritic arbors in Wernicke's area than do men (Jacobs, Schall, & Scheibel, 1993).
10. All in all, the evidence discussed gives little reason to doubt the reasoning of Skoyles (1999). It does seem, however, that we should consider the possibility that our capacity for expertise may not have been the only advantage related to humans' developing larger brains.
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