Evolutionary Psychology: A Review

3. Evolutionary Psychology Principles
and Methods

The founders of Evolutionary Psychology claim that their biologically adaptive approach can elucidate a range of human behaviours by bringing together all that we know about biology, artificial intelligence and evolutionary dynamics. The theoretical assumptions that underpin their research are listed by the founders, Tooby and Cosmides [2005], as follows.[2]

Book cover: Evolutionary Cognitive Neuroscience by Steven Platek
  1. The brain is a computer designed by natural selection to extract information from the environment.
  2. Individual human behaviour is generated by this evolved computer in response to information it extracts from the environment. Understanding behaviour requires articulating the cognitive programs that generate the behaviour.
  3. The cognitive programs of the human brain are adaptations. They exist because they produced behaviour in our ancestors that enabled them to survive and reproduce.
  4. Natural selection ensures that the brain is composed of many different special purpose programs and not a domain general architecture.
  5. Describing the evolved computational architecture of our brains 'allows a systematic understanding of cultural and social phenomena' [Tooby and Cosmides 2005: 18].

Assumption 4 rests on the veracity of the massive modularity hypothesis. This theory has gained a lot of attention and an equal amount of criticism. The hypothesis counters the theory that the mind consists of a general purpose computing device that solves problems through the application of general algorithms. In contrast, the massive modularity hypothesis specifies a large number of content-specific computing algorithms that developed independently of each other in response to selective pressures in the Pleistocene era. Evolutionary Psychologists support the hypothesis with three key arguments. These can be summarized as follows.[3]

  1. The computational modules in the human mind are analogous to organs in the body, such as the heart and liver. These developed independently as separate biological systems in response to specific environmental pressures.
  2. As there are no general problems presented by the environment, there can be no general problem solving module. Each problem is solved by a distinct computational unit.
  3. There is not enough time and information for the mind to learn from nothing all that it needs to solve the myriad of environmental problems presented to it.[4]

I will return to a consideration of the massive modularity hypothesis in §5 below.

Turning now to the methods that Evolutionary Psychologists use in their research, fundamental to their approach is the analysis of the mind's functions as a pointer to its structure. For the Evolutionary Psychologist, to show that a modern human behaviour trait is an adaption from our stone-age past, they must demonstrate that:

  1. it has many design features that are improbably well suited to solving an ancestral adaptive problem,
  2. these phenotypic properties are unlikely to have arisen by chance alone, and
  3. they are not better explained as the by-product of mechanisms designed to solve some alternative adaptive problem or some more inclusive class of adaptive problem.

[Tooby and Cosmides 2005: 28]

To achieve this, Evolutionary Psychologists use functional analysis. This is a six step procedure, outlined by Tooby and Cosmides [1989: 40–1].[5]

Step 1
uses evolutionary considerations to formulate a model of the past adaptive problems the human mind had to solve.
Step 2
generates hypotheses about exactly how these problems would have manifested themselves under the selection pressures present in the evolutionary environment of our ancestors.
Step 3
formulates a 'computational theory' that specifies 'a catalog of the specific information processing problems' [Cosmides and Tooby 1987: 289] that had to be solved to overcome the adaptive problems identified in step 2.
Step 4
uses the computational theory 'as a heuristic for generating testable hypotheses about the structure of the cognitive programs that solve the adaptive problems in question' [Cosmides and Tooby 1987: 302].
Step 5
rules out alternative accounts of the cognitive mechanisms in question that do not treat them as the result of evolution by natural selection.
Step 6
tests the adaptationist hypotheses by checking whether modern Homo sapiens indeed possess the cognitive mechanisms postulated in step 4.

Once all of the steps have been completed successfully for a specific study, then the researcher concludes that the cognitive mechanisms and the attendant behaviours tested are the result of evolutionary adaptions for the posited problem.


  1. [2] Also quoted in Downes [2010]
  2. [3] See Tooby and Cosmides [2000: 1171]. For a discussion, see [Walter 2014: §2d; Downes 2010: §3].
  3. [4] Note that this is a generalisation of Chomsky's poverty of the stimulus argument for universal grammar.
  4. [5] Also reproduced in Walter [2014: §2b].

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