CURRENT DEBATES IN EVOLUTIONARY PSYCHOLOGY:

DOMAIN-GENERAL AND DOMAIN-SPECIFIC PARADIGMS

Is the human psyche domain-general or domain-specific? Does it apply the same general-purpose reasoning power to all of the problems it encounters or does it act through mechanisms adapted to the resolution of specific tasks? Such is the question that currently divides evolutionary psychology.

This question is not new. It was central to ethology — the first discipline to analyze behaviour from an evolutionary viewpoint. Konrad Lorenz, the founder of ethology, saw its purpose as being one of breaking behaviour down into its smallest components, each of which would correspond to an innate releasing mechanism in the brain; in other words, a mechanism that releases a specific behaviour in response to a specific pattern of stimuli.

This orientation changed with the rise of sociobiology in the mid 1970s. Although the differences between ethology and sociobiology are not cut and dry, there have been real divergences in terms of agenda and research interests. Sociobiology has been strongly influenced by game theory and population genetics, with the result that it focuses more on the demographic consequences of behaviour than on its psychological antecedents. Whereas ethologists worked backwards from the study of behaviour to identify causal mechanisms, sociobiologists work forwards to see how different behavioural strategies affect reproductive success and population structure. These two approaches are not incompatible. Nonetheless, they have tended to drive people in opposing directions, eventually leading to a theoretical divergence.

Sociobiologists have had other reasons for downplaying the origins of behaviour. One was the strong backlash in the late 1970s and most of the 1980s against any research into the genetic bases of behaviour. The political agenda of that time was one of far-reaching social change, so it was to be expected that such research would be seen as an instrument for denying the possibility of change and for defending the status quo with all its attendant inequities and injustices. In addition, research into specialized sub-units of behaviour was also hampered by "physics-envy", i.e., a desire to understand all forms of behaviour in terms of a few underlying laws, processes, or mechanisms. For all these reasons, sociobiologists, much like behaviourists, chose to see the human mind as a black box and hence confine their research to the consequences of behaviour.

One result of this choice was a trend towards interest in gene-culture co-evolution, notably by Charles Lumsden and Pierre van den Berghe. Proponents of this concept hold that behaviour in the form of cultural practices can affect the course of biological evolution. One oft-cited example is lactose intolerance: most adults of European origin can easily digest milk because their bodies manufacture the enzyme for metabolizing lactose. In most other human populations, however, only infants can digest milk without suffering indigestion. The apparent reason is that European populations domesticated cattle at an early date, with the result that the possibility of adult consumption of milk has been open to them for a much longer period of time. Natural selection thus favoured adults who could exploit this potential food source.

Another trend was a premise, more often implicit than explicit, that all human behaviour is guided by a generalized fitness maximizer. It is unclear whether this is considered to be a centralized mechanism within the brain that pushes all behaviour in the direction of maximizing fitness or whether it is simply a metaphor — a guiding hand which incarnates processes of cultural evolution that are analogous to those of biological evolution, i.e. a behaviour which maximizes reproductive fitness is favoured because the people who learn it within the family are also its beneficiaries. Thus, even in the absence of genetic transmission, cultural traits that promote fitness can still be favoured by a process that mimics natural selection.

Beginning in the late 1980s, the refusal of sociobiology to address the origins of behaviour came increasingly under attack from certain evolutionary psychologists, notably Donald Symons (1989), John Tooby and Leda Cosmides (1989), and David Buss (1991). Buss, Tooby, and Cosmides adopted a theoretical line of attack. The idea of a domain-general fitness maximizer was criticized as being at best a vague metaphor and at worst an incoherent and misleading concept. They also contended that insofar as the demands of different adaptive tasks are different in nature, and more efficiently solved using different means, psychological mechanisms would tend, over time, to multiply in number and differentiate in procedure.

Buss, Tooby, and Cosmides also argued that to the extent human behaviour uses innate psychological mechanisms, such mechanisms would reflect adaptations to our ancestral Pleistocene environment and not to present-day conditions, as gene-culture co-evolution would have it. Even supposedly simple cognitive tasks require complex processing of information, so that a domain-specific mechanism specialized in the resolution of a given task could not have evolved quickly, certainly not as fast as cultural evolution. Gene-culture co-evolution should be limited to single-gene substitutions that might modify the sensitivity of existing mechanisms but would not create new ones.

Donald Symons echoed these criticisms while emphasizing the inability of the domain-general paradigm to produce original or interesting findings. There is nothing terribly novel in saying that humans attach a lot of importance to reproduction. As Symons sarcastically noted, human action obviously is not random with respect to reproduction, but surely no one, and no theoretical perspective, ever supposed that it was. Evolutionary anthropologists, for example, are saying nothing new when they state that economic relationships are not the ultimate determining factor in traditional societies and that kinship, sexuality, and reproduction are determinants in their own right. They are simply repeating what used to be said before the rise of Marxist anthropology and which is now being said again by disillusioned Marxists. Maurice Godelier, for one:

It was a mistake to want to establish a correspondence between the modes of production and the structures of kinship. The structures of kinship are autonomous. Just as, moreover, the systems of representation, religion for example. One cannot interpret all of social life from the economy, as if the economy were the general foundation of social life.

These criticisms have elicited some reaction from defenders of the domain-general paradigm, notably Kevin MacDonald (1991). An article he recently wrote shows some degree of rapprochement between domain-general and domain-specific thinking. MacDonald discards the notion of a single domain-general fitness maximizer and recognizes the existence of domain-specific mechanisms. This rapprochement can be continued if we stop thinking of domain-specific and domain-general as being two opposite poles with nothing inbetween. It is perhaps better to think in terms of a continuum ranging from mechanisms whose algorithms have been almost entirely hardwired to those whose algorithms are little more than a frame whose missing parts are later filled in by learning, imprinting, and other forms of softwiring.

We are only just beginning to map out the design and structure of these algorithms which make up the human psyche (Anon 1992). Such an endeavour will prove to be as monumental as the current effort to map the human genome. If the Human Genome Project is any guide, it will capture the imagination not only of academic and scientific circles but also of the public at large.

Bibliography

Anon. "A critique of pure reason" The Economist pp. 73-74, July 4, 1992

Buss, David M. 1991 "Evolutionary Personality Psychology", Annual Review of Psychology 42: 459-491.

Godelier, M. 1993. "Un anthropologue aux rêves bousillées" Le Devoir, May 6, 1993.

MacDonald, Kevin 1991 "A Perspective on Darwinian Psychology: The Importance of Domain-General Mechanisms, Plasticity, and Individual Differences", Ethology and Sociobiology 12: 449-480.

Symons, Donald 1989 "A Critique of Darwinian Anthropology", Ethology and Sociobiology 10: 131-144.

Tooby, John and Leda Cosmides 1989 "Evolutionary Psychology and the Generation of Culture, Part I - Theoretical Considerations", Ethology and Sociobiology 10: 29-49.