Why humans are (sometimes) less rational than other animals: Cognitive complexity and the axioms of rational choice

Abstract

Several formal analyses in decision theory have shown that if people's preferences follow certain logical patterns (the so-called axioms of rational choice) then they are behaving as if they are maximising utility. However, numerous studies in the decision-making literature have indicated that humans often violate the axioms of rational choice. Additionally, studies of nonhuman animals indicate that they are largely rational in an axiomatic sense. It is important to understand why the finding that humans are less rational than other animals is not paradoxical. This paper discusses three reasons why the principles of rational choice are actually easier to follow when the cognitive architecture of the organism is simpler: contextual complexity, symbolic complexity, and the strong evaluator struggle.

Keywords:

• Cognitive complexity
• Axioms of rational choice
• Decision making
• Context and values

Notes

¹The same principle suggests that when pure consistency is the definition of rationality, people primed to use only Type 1 processing (Evans, 2008, 2010) might achieve better results than those using a mixture of Type 1 and Type 2 processing (see Lee, Amir, & Ariely, 2009; Reyna, 2004; Wilson & Schooler, 1991).

²In philosophical discussions the issue of how the alternatives should be contextualised is termed the problem of the eligibility of interpretations (see Hurley, 1989, pp. 55–106) or the construal problem (Stanovich, 1999, Ch. 4).

³Of course the joke here is that if nonhuman animals could understand the instructions of the experiment, they would be nearly human and probably respond as humans do. Nonetheless it should be noted that, in repeated iterations of such a game, it is an open question whether any higher primate might be able to learn to use punishing refusals to shape the partner's response. Jensen, Call, and Tomasello (2007) set up a version of the Ultimate Game for chimpanzees and claimed that, unlike humans, the chimpanzees showed maximising behaviour and thus were not sensitive to fairness. Knoch, Pascual-Leone, Meyer, Treyer, and Fehr (2006) found that, in humans, disrupting the right dorsolateral prefrontal cortex (DLPFC) with repetitive transcranial magnetic stimulation resulted in more acceptances of low unfair offers. Their finding suggests that the inhibitory powers of the DLPFC are used to suppress the response that would represent narrow instrumental rationality in the task. The DLPFC appears to be used to implement a goal of fairness—one that sacrifices utility maximisation narrowly construed. Lakshminarayanan and Santos (2009) claim to have shown that capuchin monkeys possess at least some of the inhibitive capacities that the Ultimatum Game requires.

⁴Msetfi, Murphy, Simpson, and Kornbrot (2005) describe a study in which control participants displayed less-rational response patterns in a contingent judgement task than did schizophrenic participants because the latter were less prone to process contextual features of the experiment (see also Bachman & Cannon, 2005; Sellen, Oaksford, & Gray, 2005).

⁵There of course is no limit to the hierarchy of higher-order desires that might be constructed. But the representational abilities of humans may set some limits— certainly three levels seems a realistic limit for most people in the nonsocial domain (Dworkin, 1988). However, third-order judgements can be called upon to help achieve rational integration at lower levels. So, for example, John, the smoker, might realise when he probes his feelings that:

He prefers his preference to prefer not to smoke over his preference for smoking:

[(∼S pref S) pref (S pref ∼S)] pref [S pref ∼S]

We might in this case say that John's third-order judgement has ratified his second-order strong evaluation. Presumably this ratification of his second-order judgement adds to the cognitive pressure to change the first-order preference by taking behavioural measures that will make change more likely (entering a smoking secession programme, consulting his physician, asking the help of friends and relatives, staying out of smoky bars, etc.).

Additional information

Notes on contributors

Keith E. Stanovich

Preparation of this manuscript was supported by the Canada Research Chairs program and the Grawemeyer Award in Education