Character  &  Context

Rationalizing the “Irrational”

Image of smoldering, smoky cigarette butts in an ashtray

Economists are famous for attempting to rationalize seemingly irrational behavior. One of the more extraordinary is Gary Becker and Kevin Murphy’s theory of rational addiction, in which they hypothesized that addicts plan their consumption of addictive goods. When deciding whether to smoke a cigarette or take a hit, the theory goes, addicts choose in full knowledge and consideration of the health costs and the future costs of their smoking or drug use due to addiction.

It’s tempting to claim that others’ actions are irrational; to delay such judgement involves a healthy degree of humility. After all, an external witness to a person’s actions doesn’t know what that person’s objectives are. But attempting to rationalize every behavior is also risky (as in policing and crime, for example), making it difficult to simply declare there is alignment between objectives and actions.

If we wish to assess whether someone’s actions are likely to achieve their objectives, we need an alternative way to understand what that person’s objectives are. And one place that might provide insight into these objectives is evolutionary biology.

Every person is the product of billions of years of natural selection. Without fail, every one of our ancestors managed to survive to reproductive age, find a partner to reproduce with (at least since the advent of sexual reproduction 1.2 billion years ago) and have offspring that in turn survived to reproductive age. The result is a mind and body selected to have preferences that would tend to result in survival and reproduction and the continuation of one’s evolutionary line.

Of course, evolution does not shape our preferences to explicitly seek these objectives. With few exceptions most of us don’t spend our time plotting how we can maximize our reproductive output. Rather, evolution shapes our preferences so that we seek proximate objectives that, at least in the environment they were shaped in, led to our ancestors surviving, attracting partners, and having offspring that survived.

Some of these preferences are obvious. A desire to have sex—(largely) necessary to pass on your genes, although today often thwarted by birth control. A taste for fatty and sweet foods—quite useful in a calorie-constrained environment, but not without problems in today’s abundance. A desire for relative status to attract partners—still important. A strong bond to those otherwise income- and leisure- reducing children—with the modern welfare state, not quite as critical to child survival as it once was.

When we examine objectives from an evolutionary biology perspective, we see that what appears irrational might simply be a misunderstanding on our part of what someone’s objectives are.

Some parts of economics and behavioral science indirectly tap into an understanding of the types of preferences likely to have evolved. From the economists, resources and consumption are important to survival. From the behavioral scientists, social norms reflect our need for status and the way we learn the skills we need to survive. But in many ways the surface has only been scratched.

Continue reading the post by visiting Behavioral Scientist.


Jason Collins is data science lead with Australia's corporate, markets, and financial services regulator. He specializes in economics, evolution, and behavioral science.

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