Bad reasoning about reasoning

by Massimo Pigliucci

A recent paper on the evolutionary psychology of reasoning has made mainstream news, with extensive coverage by the New York Times, among others. Too bad the “research” is badly flawed, and the lesson drawn by Patricia Cohen’s commentary in the Times is precisely the wrong one.

Readers of this blog and listeners to our podcast know very well that I tend to be pretty skeptical of evolutionary psychology in general. The reason isn’t because there is anything inherently wrong about thinking that (some) human behavioral traits evolved in response to natural selection. That’s just an uncontroversial consequence of standard evolutionary theory. The devil, rather, is in the details: it is next to impossible to test specific evopsych hypotheses because the crucial data are often missing. The fossil record hardly helps (if we are talking about behavior), there are precious few closely related species for comparison (and they are not at all that closely related), and the current ecological-social environment is very different from the “ERE,” the Evolutionarily Relevant Environment (which means that measuring selection on a given trait in today’s humans is pretty much irrelevant).

That said, I was curious about Hugo Mercier and Dan Sperber’s paper, “Why do humans reason? Arguments for an argumentative theory,” published in Behavioral and Brain Sciences (volume 34, pp. 57-111, 2011), which is accompanied by an extensive peer commentary. My curiosity was piqued in particular because of the Times’ headline from the June 14 article: “Reason Seen More as Weapon Than Path to Truth.” Oh crap, I thought.

Mercier and Sperber’s basic argument is that reason did not evolve to allow us to seek truth, but rather to win arguments with our fellow human beings. We are natural lawyers, not natural philosophers. This, according to them, explains why people are so bad at reasoning, for instance why we tend to fall for basic mistakes such as the well known confirmation bias — a tendency to seek evidence in favor of one’s position and discount contrary evidence that is well on display in politics and pseudoscience. (One could immediately raise the obvious “so what?” objection to all of this: language possibly evolved to coordinate hunting and gossip about your neighbor. That doesn’t mean we can’t take writing and speaking courses and dramatically improve on our given endowment, natural selection be damned.)

The first substantive thing to notice about the paper is that there isn’t a single new datum to back up the central hypothesis. It is one (long) argument in which the authors review well known cognitive science literature and simply apply evopsych speculation to it. If that’s the way to get into the New York Times, I better increase my speculation quotient.

The second thing that ought to strike the reader as strange is the very idea that one can meaningfully talk about “reasoning” as if it were a well defined biological trait, like having a prehensile tail. Reasoning is a complex activity that draws on a variety of brain structures that certainly predated the “evolution” of reasoning itself, which means that — at best — natural selection has co-opted bits and pieces of those structures as in a sort of Rube Goldberg contraption. That would account for the “puzzling” fact that human reasoning is so prone to failure.

Moreover, as commentator Darcia Narvaez (University of Notre Dame) put it in the Times article, “reasoning is something that develops from experience” and language — which is necessary to communicate our reasoning (and therefore for arguing) — is a very late comer in human evolution. The unspoken corollary being that therefore there has been comparatively little time for natural selection to have much of an impact.

Things get even more odd if one begins to pick apart the Mercier and Sperber paper. They start out by saying that “we outline an approach to reasoning based on the idea that the primary function for which it evolved is the production and evaluation of arguments in communication.” But this assumes, again, that “reasoning” is a sufficiently coherent biological trait that historically took on a well defined “function,” none of which is at all uncontroversial or well established.

But the real problem with the paper comes near the end, when the authors have to admit that human reasoning actually works pretty darn well — when it is used in a group context and people are motivated to seek the truth (as opposed to an individual context, or when people are motivated by personal gain). For instance:

“In group reasoning experiments where participants share an interest in discovering the right answer, it has been shown that truth wins ... In these group tasks, individual participants come up with and propose to the group the same inappropriate answers that they come up with in individual testing. The group success is due to, first and foremost, the filtering of a variety of solutions, achieved through evaluation. ... Reasoning is responsible for some of the greatest achievements of human thought in the epistemic and moral domains. This is undeniably true, but the achievements involved are all collective and result from interactions over many generations.”

No kidding. There is absolutely nothing new here. For instance, sociologist and philosopher Helen Longino has long pointed out that science itself works because it is a social process of continuous peer review, where individual biases are countered by other individual biases (and by the existence of an actual physical world that doesn’t care about human biases). So it turns out that it isn’t that humans are bad at reasoning, but rather that reasoning itself is an inherent social activity, that works well in a group context. Is this a different phenomenon from individual reasoning? Is this too the result of natural selection? At the group level, perhaps? Mercier and Sperber do not say.

There also seems to be a basic logical flaw in the authors’ argument. When, for instance, they say: “in most discussions, rather than looking for flaws in our own arguments, it is easier to let the other person find them and only then adjust our arguments, if necessary.” That may very well be true, but wouldn’t that select for better and better ways to spot bad arguments in other people’s reasoning? And wouldn’t that lead to the evolution of near-perfect logicians? You see how easy it is to spin evopsych scenarios?

Moreover, there is a question of how necessary the invocation of a new theory actually is in this context. Again Mercier and Sperber: “True, most of [our] predictions can be derived from other theories ... In our discussion of motivated reasoning and of reason-based choice, not only did we converge in our prediction with existing theories, but we also extensively borrowed from them.” Oh, so other explanations are both possible and viable, and there are no new data to discriminate among the offerings. Do I smell pseudoscience here?

Finally, a comment on the way these “findings” have been reported. While the Times article is actually a pretty good reflection of the paper itself (and of the peer commentaries thereof), the tone and particularly the title suggest that philosophers, logicians and the like have been misguided in their insistence on the power of human reason. But if anything Mercier and Sperber’s theory (or, more seriously, the vast literature on cognitive biases) argues that we need philosophy, logic, science and critical thinking all the more — as a counter to the natural tendency of humanity to think badly. When commenting on the fact that a relatively small percentage of people is capable of sound reasoning (for instance in the famous Wason selection task — which I teach in my critical reasoning course), the authors say: “this is an acquired skill and involves exercising some imperfect control over a natural disposition that spontaneously pulls in a different direction.” Right, and those skills are honed precisely by studying and by exposing people to constant (as rational as we can muster) dialogue. I wonder why that little observation didn’t make it into the Times article.