Why do humans reason? Arguments for an argumentative theory

Commentary/Mercier & Sperber: Why do humans reason?Table 1 (Poletiek). Utilities of reasoning outcomes about H (thereasoner’s subjective belief), assuming an epistemic motive (A), anargumentative motive (B), and both types of motives (C).their expectation of the outcome that changed when they tested ahypothesis they did not believe to be true (falsification wasexpected). When testing their best guess, they expected a confirmingoutcome.Besides determining the truth, many considerations may affecthow we reason and whether we reason. These considerations canbe modeled as a cost-benefit analysis of making the right inference.In Wason’s (1960) task, students participating in the experimentmight not care much about making reasoning errors. Thekey seeker might perform a negative test (looking for the keys insome place other than the jacket) because the costs of a positiveone are too high: The jacket was left behind in a friend’s houseand the effort too great to walk back to check the jacket. Alternatively,we might be in a hurry and have time to check just onelocation, enhancing the benefits of good reasoning.To predict reasoning behavior, we need a model with utilitiesof reasoning outcomes. A suitable tool is signal-detection theory.Motives can be expressed in the utilities of inference errors andin reasoning behavior predicted on the basis of the risk we areprepared to take with regard to particular erroneous inferences(Poletiek & Berndsen 2000). For example, as shown in Table 1,a pure epistemic motive would be modeled with (A) low utilitiesof making any false inferences. A pure argumentative motivewould be expressed in (B) a very high willingness to make thefalse inference that our favorite hypothesis is true; and (C)reasoning with both motives (searching for a valid inferencewithin both practical or argumentative constraints) is reflectedwith some in-between utilities with regard to making a false ora correct inference about our favorite hypothesis.In this manner, reasoning in a variety of contexts and with avariety of goals can be modeled, offering an elegant alternativeto the paradox of the ATR that we start up a reasoning trajectoryabout a prior belief if and only if the end of the route leads us toinferring that belief again.When reasoning is persuasive but wrongdoi:10.1017/S0140525X10002761Robert J. SternbergAH is trueInfer H 10 0Infer not-H 0 10Infer H 10 10Infer not-H 0 0Infer H 10 4Infer not-H 0 6BCNot-H is trueProvost and Senior Vice President, Oklahoma State University, Stillwater, OK74078.Robert.sternberg@okstate.eduAbstract: Mercier and Sperber (M&S) are correct that reasoning andargumentation are closely related. But they are wrong in arguing thatthis relationship is one of evolutionary adaptation. In fact, persuasivereasoning that is not veridical can be fatal to the individual and to thepropagation of his or her genes, as well as to the human species as awhole.In the target article, Mercier & Sperber (M&S) brilliantly show acrucial relationship between argumentation and reasoning. Butthe relationship is not the one they claim to show.Consider two individuals facing an adaptive challenge. A threatof some kind is about to confront them. One of the individuals, A,recognizes the threat; the other, B, fails, for whatever reason, torecognize it. The two individuals argue over the existence of thethreat or, perhaps, its severity. Each argues compellingly for hisor her point of view. After all, with inductive reasoning basedon incomplete and often ambiguous information, arguments canhave inductive strength but not deductive certainty; and theirinductive strength does not necessarily correspond to their veridicality(as anyone will have observed who has seen a defense attorneygets off his guilty client scot free). A and B both act on thebasis of their reasoning. A survives and B dies (as a result of abear attack, a lightning strike, an automobile accident, a planecrash, or whatever the threat in question happened to be).A and B both used their reasoning in the service of argumentation,but reasoning was adaptive by virtue of the veridicality of itsconclusion, not by virtue of the persuasiveness of the arguments(which may or may not correspond to veridicality in real-worldambiguous situations with incomplete information). So reasoningcould scarcely have evolved in the service of argumentation,because those wonderful arguers who did not perceive thingsveridically would have been less able to reproduce than thosearguers who did perceive things veridically. The brilliant reasonerswho argued wrongly regarding threats had many more opportunitiesto perish before reproducing than those reasoners,persuasive or not, who saw threats as they were.The same phenomenon occurs at a group level. Consider globalwarming. Global warming threatens the existence of human andother life on the planet Earth, and yet deniers, including scientists,put the life of all human organisms on the planet – the replicationof the species’ genes and hence the survival of the species– at risk. Reasoning is being used in the service of argumentation,but not always for evolutionarily adaptive purposes, at least withrespect to the genes of the individuals involved.The opening view of M&S that “reasoning should produce itsbest results when used in argumentative contexts, most notably ingroup discussions” (sect. 1.2, para. 11) is clearly wrong, as are thearguments that follow from it. The problem is that in this quotation,as throughout the article, there is an ambiguity regardingthe meaning of “best results.” If reasoning is about persuasiveness,perhaps the authors are right. But if reasoning is about veridicality,they are wrong.Janis (1972) recognized the fallacy of the reasoning in his workon groupthink. He observed that groups of academically brilliantgovernment officials could make horrible mistakes that wereactually compounded by their being in groups. More generally,the phenomenon is referred to as “group polarization” (Moscovici& Zavalloni 1969). People like Robert McNamara and,more recently, Donald Rumsfeld, come to mind – people who,despite their academic brilliance, reasoned poorly, yet wereable to persuade many by their (false) arguments. Stanovich(1993; 2009) coined the irrational but often persuasive reasoningof IQ-smart people “dysrationalia” (for related ideas, see alsoSternberg 2002).In the short run, reasoning in the service of argument may wellbe adaptive. For example, a job candidate who is persuasive isperhaps more likely to get the job than one who is unpersuasive;a politician who is persuasive is more likely to be elected or, atleast, to be believed. But as recent presidential and other electionshave shown, persuasiveness (at least to the masses) can beattained even by candidates who cannot string together a88 BEHAVIORAL AND BRAIN SCIENCES (2011) 34:2