The evolution of reason

Mercier, H. 2010, “The Social Origins of Folk Epistemology“, Review of Philosophy and Psychology

In this paper, Mercier argues that an evolutionary account of reasoning that derives from social argumentation is more compelling than the classic view which frames it as a crown jewel of individual cognition. He sees reasoning as a necessary outcome of human communication, where the responder employs sophisticated coherence checking of newly received facts (tending towards conserving existing knowledge), and the sender employs techniques to select the most convincing premises to persuade the receiver (while striving to avoid an irreversible loss of trust).

Mercier draws support for this theory from the observations that:

  1. Confirmation and disconfirmation bias are a common and robust experimental finding, with people finding support for their side of an issue much more readily than the other side;
  2. Individual reasoning doesn’t necessarily lead to better decisions, and here Mercier cites evidence for poorer decisions when people are asked to consciously and explicitly consider their reasons first.
  3. Individual reasoning tends toward options that are easier to justify, and this may lead people away from normative answers toward those that would be easier to defend if called upon to do so.

Individual reasoning is therefore “a tool of (anticipated) persuasion”. Groups can perform better, on the other hand, perhaps due to a fairer balance between evaluation and persuasion. Here Mercier cites the “truth wins” and “assembly bonus effects”, where groups converge on correct answers, even where no individual members have these answers to begin with. In ideal social argumentation, the net effect can approach unbiased reasoning, because the type of biases named above provide the means to divide labour (each person only needs to find arguments for their own position and these are judged by the rest of the group on their merits).

Mercier does not always explain the evidence that he draws on very clearly, and it is tempting to wonder if he is exhibiting confirmation bias himself. Clearly neither the shortcomings of individual reasoning nor the merits of group decision making should be over-generalised. That said, there seems intuitively (i.e before engaging reason!?) to be much value in his approach in seeking a social, relationist origin to this cognitive capability. These ideas seem to fit well with that of enactive cognition – that individual cognitive structures are a consequence of a structurally coupled social system – and social epistemology, that social evidence should be considered a valid and primary source of knowledge.

One thought on “The evolution of reason

  1. Hugo Mercier

    Thank you for your kind review of this paper. I certainly hope that I displayed a confirmation bias, I wouldn’t want to prove the theory wrong even while arguing for it!
    The fundamental idea (reasoning is for argumentation) is actually not mine, but that of Dan Sperber (see this paper for instance:
    We have elaborated on it in a number of papers, most notably this one:


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