Criticism of Evolutionary Psychology - Testability

Testability

A frequent critique of EP is that its hypotheses are difficult or impossible to adequately test, challenging its status as an empirical science. As an example, critics point out that many current traits likely evolved to serve different functions than they do now, confounding attempts to make backward inferences into history. Evolutionary psychologists acknowledge the difficulty of testing their hypotheses but assert it is nevertheless possible.

Critics argue that many hypotheses put forward to explain the adaptive nature of human behavioural traits are "just-so stories"; neat adaptive explanations for the evolution of given traits that do not rest on any evidence beyond their own internal logic. They allege that evolutionary psychology can predict many, or even all, behaviours for a given situation, including contradictory ones. Therefore many human behaviours will always fit some hypotheses. Noam Chomsky argued:

"You find that people cooperate, you say, ‘Yeah, that contributes to their genes' perpetuating.’ You find that they fight, you say, ‘Sure, that’s obvious, because it means that their genes perpetuate and not somebody else's. In fact, just about anything you find, you can make up some story for it."

Leda Cosmides argued in an interview:

"Those who have a professional knowledge of evolutionary biology know that it is not possible to cook up after the fact explanations of just any trait. There are important constraints on evolutionary explanation. More to the point, every decent evolutionary explanation has testable predictions about the design of the trait. For example, the hypothesis that pregnancy sickness is a byproduct of prenatal hormones predicts different patterns of food aversions than the hypothesis that it is an adaptation that evolved to protect the fetus from pathogens and plant toxins in food at the point in embryogenesis when the fetus is most vulnerable – during the first trimester. Evolutionary hypotheses – whether generated to discover a new trait or to explain one that is already known – carry predictions about the nature of that trait. The alternative – having no hypothesis about adaptive function – carries no predictions whatsoever. So which is the more constrained and sober scientific approach?"

A 2010 review article by evolutionary psychologists describes how an evolutionary theory may be empirically tested. An hypothesis is made about the evolutionary cause of a psychological phenomenon or phenomena. Then the researcher makes predictions that can be tested. This involves predicting that the evolutionary cause will have caused other effects than the ones already discovered and known. Then these predictions are tested. The authors argue numerous evolutionary theories have been tested in this way and confirmed or falsified. Buller (2005) makes the point that the entire field of evolutionary psychology is never confirmed or falsified; only specific hypotheses, motivated by the general assumptions of evolutionary psychology, are testable. Accordingly he views evolutionary psychology as a paradigm rather than a theory, and attributes this view to prominent evolutionary psychologists including Cosmides, Tooby, Buss, and Pinker.

In his review article Discovery and Confirmation in Evolutionary Psychology (in The Oxford Handbook of Philosophy of Psychology) Edouard Machery concludes:

"Evolutionary psychology remains a very controversial approach in psychology, maybe because skeptics sometimes have little first-hand knowledge of this field, maybe because the research done by evolutionary psychologists is of uneven quality. However, there is little reason to endorse a principled skepticism toward evolutionary psychology: Although clearly fallible, the discovery heuristics and the strategies of confirmation used by evolutionary psychologists are on a firm grounding."