Natural Rationality | decision-making in the economy of nature


Natural Rationality for Newbies

Decision-making, as I routinely argue in this blog, must be understood as entrenched in a richer theoretical framework: Darwin’s economy-of-nature. According to this principle, animals could be modeled as economic agents and their control systems could be modeled as economic devices. All living beings are thus deciders, strategists or traders in the economy of reproduction and survival.

When he suggested that nature is an economy, Darwin paved the way for a stronger interaction between biology and economics. One of the consequences of a bio-economic approach is that decision-making becomes an increasingly important topic. The usual, commonsense construal of decision-making suggests that it is inherently tied to human characteristics, language in particular. If that is the case, then talk of animal decisions is merely metaphorical. However, behavioral ecology showed that animals and human behavior is constrained by economic parameters and coherent with the economy-of-nature principle. Neuroeconomics suggest that the neural processing follow the same logic. Dopaminergic systems drive animals to achieve certain goals while affective mechanisms place goals and action in value spaces. These systems, although they were extensively studied in humans, are not peculiar to them: humans display a unique complexity of goals and values, but this complexity relies partly on neural systems shared with many other animals: the nucleus accumbens and the amygdala, for instance are common in mammals. Brainy animals evolved an economic decision-making organ that allows them to cope with complex situations. As Gintis remarks, the complexity and the metabolic cost of central nervous systems co-evolved in vertebrates, which suggests that despite their cost, brains are designed to make adaptive decision[i].

Hence decision-making should be analyzed similarly as, and occupies an intellectual niche analogous to, the concept of cooperation. Nowadays, the evolutionary foundations, neural substrates, psychological mechanisms, formal modeling and philosophical analyses of cooperation constitutes a coherent—although not unified—field of inquiry [ii]. The nature of prosocial behavior, from kin selection to animal cooperation to human morality, is best understood by adopting a naturalistic stances that highlights both the continuity of the phenomenon and the human specificity. Biological decision-making deserves the same eclecticism.

Talking about biological decision-making comes at a certain conceptual price. As many philosophers pointed out, whenever one is describing actions and decisions, one is also presupposing the rationality of the agent[iii]. When we say that agent A chose X, we suppose that A had reasons, preferences, and so on. The default assumption is that preferences and actions are coherent: the firsts caused the seconds, and the seconds are justified by the firsts. The rationality philosophers are referring to, however, is a complex cognitive faculty, that requires language and propositional attitudes such as beliefs and desires. When animals forage their environment, select preys, patches, or mates, no one presupposes that they entertain beliefs or desires. There is nonetheless a presupposition that “much of the structure of the internal mental operations that inform decisions can be viewed as the product of evolution and natural selection”.[iv] Thus, to a certain degree, the neuronal processes concerned with the use of information are effective and efficient, otherwise natural selection would have discarded them. I shall label these presuppositions, and the mechanisms it might reveal, “natural rationality”. Natural rationality is a possibility condition for the concept of biological decision-making and the economy-of-nature principle. One needs to presuppose that there is a natural excellence in the biosphere before studying decisions and constraints.

More than a logical prerequisite, natural rationality concerns the descriptive and normative properties of the mechanisms by which humans and other animals make decisions. Most concepts of rationality take only the descriptive or the normative side, and hence tend to describe cognitive/neuronal processes without concern for their optimality, or state ideal conditions for rational behavior. For instance, while classical economics considers rational-choice theory either as a normative theory or a useful fiction, proponents of bounded rationality or ecological rationality refuse to characterize decision-making as optimization.[v] Others advocate a strong division of labor between normative and descriptive project: Tversky and Kahneman, for instance, concluded from their studies of human bounded rationality that the normative and descriptive accounts of decision-making are two separate projects that “cannot be reconciled”[vi]

The perspective I suggest here is that we should expect an overlap between normative and descriptive theories, and that the existence of this overlap is warranted by natural selection. On the normative side, we should ask what procedures and mechanisms biological agents should follow in order to make effective and efficient decision given all their constraints in the economy of nature. On the descriptive side, we must assess whether a procedure succeeds in achieving goals or, conversely, what goals could a procedure aim at achieving. If there is no overlap between norms and facts, then either norms should be reconceptualized or facts should be scrutinized: it might be the case that norms are unrealistic or that we did not identify the right goal or value.

This accounts contrasts with philosophers (e.g. Dennett or Davidson) who construe rationality as an idealization and researchers who preach the elimination of this concept because of its idealized status (evolutionary psychologists, for instance[vii]). Thus, rationality can be conceived not as an a priori postulate in economy and philosophy, but as an empirical and multidisciplinary research program. Quine once said that “creatures inveterately wrong in their inductions have a pathetic but praiseworthy tendency to die out before reproducing their kind”[viii]. Whether it is true for inductions is still open to debate, but I suggest that it clearly applies to decisions.

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Notes and references
  • [i] (Gintis, 2007, p. 3)
  • [ii] See for instance how neuroscience, game theory, economic, philosophy, psychology and evolutionary theory interact in (E. Fehr & Fischbacher, 2002; Ernst Fehr & Fischbacher, 2003; Hauser, 2006; Penner et al., 2005).
  • [iii] (Davidson, 1980; Dennett, 1987; Popper, 1994).
  • [iv] (Real, 1994, p. 4)
  • [v] (Chase et al., 1998; Gigerenzer, 2004; Selten, 2001)
  • [vi] (Tversky & Kahneman, 1986, p. s272)
  • [vii][vii] (Cosmides & Tooby, 1994)
  • [viii] (Quine, 1969, p. 126)


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