Since the 1970s, behavioral economists — from Daniel Kahneman and Amos Tversky to Cass Sunstein and Richard Thaler — have been chipping away at the idea that human beings are basically rational creatures. Their work has suggested that we’re actually a lot more irrational than we think.

That’s caused no small amount of hand-wringing: Humans were supposed to be “the rational animal”! Are we instead just doomed to keep making lots of terrible decisions?

New research says there’s another way to look at it. What if people often choose to be irrational in cases where doing the rational thing would violate something they value more — like socially conscious behavior? And if that’s the case, should we actually embrace some instances of irrationality rather than discounting it as an embarrassing nuisance?

That’s one of the possibilities raised in an interesting psychology study published last week in Science Advances. Researchers based at the University of Waterloo in Canada wanted to understand what prompts people to use rationality — or deviate from it — in their decision-making. To get at this, they first analyzed reams of text to see what people generally take rationality to mean. Then they conducted 12 experiments, recruiting people from Amazon Mechanical Turk to play classic economic games like the Dictator Game online and answer questions about their behavior.

The study starts by distinguishing between two terms: there’s rationality, where you focus on maximizing the chance of getting what you want, and there’s reasonableness, where you strike a balance between what you want and social norms.

Although we might sometimes use rational and reasonable interchangeably, the study shows that people generally associate the former with the cold hard logic of self-interest and the latter with socially conscious traits like kindness or cooperativeness. A computerized analysis of billions of words — drawn from soap operas, Supreme Court opinions, and Google Books — showed that these associations hold true across several countries.

But is it better to act rationally or reasonably? The researchers conducted some experiments to understand people’s perceptions, expectations, and behaviors. Here are five key findings:

Participants perceived reasonable people as less selfish than rational people.

Participants expected that reasonable people would share more than rational people.

Their expectation turned out to be correct: People who viewed themselves as reasonable shared significantly more than those who viewed themselves as rational.

In a Dictator Game, an experiment where you’re given money and have to decide whether to give some of it away, participants donated 5 percent more money if they were aiming to be reasonable than if they were aiming to be rational.

When participants were asked to recall either reasonable or rational actions from their lives, and then to take part in a Dictator Game, it turned out that recalling a reasonable action led to offers that were slightly higher than did recalling a rational action. Plus, whereas 14 percent of participants in the rational condition wanted to donate nothing, only 9.5 percent of those in the reasonable condition said the same (in fact, 71 percent of them donated at least half the money).

Together, these findings offer us insights that cut against our inherited ways of thinking about what constitutes sound decision-making. Ditching rationality in favor of reasonableness might actually make sense in some contexts, they suggest — especially because we’ve lately defined rationality in such a narrow way that it’s just not always the most useful standard of judgment.

Is it better to be rational or reasonable? It depends on your goals.

One of the noteworthy things in this study is that simple linguistic cues — rational versus reasonable — are effective at influencing participants’ behavior in a pretty consistent way.

The fact that participants donated more generously when primed to think about reasonableness may have implications for fields like education, politics, advocacy, and marketing. “To encourage people to make more cooperative choices,” the study suggests, “reduce the demand to be rational and enhance the request to be reasonable.”

Say you want to mitigate climate change and you’re trying to convince people to accept a carbon tax. You could tell them it’s the rational thing to do because it’ll end up putting money back into their pockets — in other words, it’s in their self-interest. Or you could tell them it’s only reasonable to embrace a policy that will ensure a better future for their children, their country, and their planet.

Igor Grossmann, the study’s lead author and an associate professor of psychology at the University of Waterloo in Canada, told me he’s noticed many advocates in that country using the first approach. He thinks that’s a mistake.

“When you’re arguing for a behavior that’s for the common good,” he told me, “you may be more successful with the reasonableness frame” — especially when the behavior requires a bit of initial sacrifice on the self-interest front, as a carbon tax does.

In other cases, however, embracing rationality can serve you better.

The researchers asked participants to imagine that they were caught up in a negotiation or legal dispute. Who would they rather have acting on their behalf: a rational agent or a reasonable agent? Participants favored the rational agent — which makes sense, because they’re looking for someone who’ll keep them from getting a raw deal or a prison sentence.

The point, the authors say, is that “preferences for rational or reasonable agents are conditional on situational goal demands.”

This echoes recent research by other psychologists like Molly Crockett at Yale, who has shown that we prefer different types of moral agents in different social roles. When we’re looking for a spouse or a friend, we prefer deontologists, who believe that an action is moral if it’s fulfilling a duty — and that we have special duties toward special people like our partners and pals. But when we’re looking for a political leader, we prefer utilitarians or consequentialists, who believe that an action is moral if it produces good consequences — and that everyone equally deserves to benefit from the good.

In the moral domain, applying deontology in some cases and consequentialism in others might come off as inconsistent. Yet it may actually be the wisest thing to apply different moral philosophies in different relational contexts.

And the same may be true in the realm of decision-making.

“Irrational behavior,” says the study, “may not necessarily be a sign of failure to understand game theoretical principles but rather an attempt to follow a competing folk standard of reasonableness.”

That’s academese for: When you see someone acting in a way that seems irrational and you’re tempted to write that off as a stupid mistake, think again. Maybe they’re not failing at rational decision-making. Maybe they’re succeeding at reasonable decision-making, which they’ve deemed more appropriate for that situation.

We need to recover a richer notion of rationality

Let’s get clear on something: Nobody is arguing that rationality is a bad thing. It’s more that our understanding of rationality has, over the past few decades, become impoverished.

“What philosophers since the Enlightenment meant by rationality is much more complex than what economists talk about now,” Grossmann told me. “If you look at Immanuel Kant or Adam Smith, their notion of rationality is much more nuanced and it does include social norms. Yet behavioral economists have this very narrow notion of rationality: abstract, formal, self-interested, and not at all about social norms.”

In other words, rationality used to be this capacious concept that included reasonableness. By ripping reasonableness out of it, we ended up with a standard of judgment that the average person won’t see fit to apply in all situations — and then we assumed that indicates there’s something wrong with them.

According to Grossman, we’ve lost the more useful notion of rationality, but “the reasonableness standard can help to recover it.”

We shouldn’t extrapolate too much from this single study of his. It’s got its limitations. For example, although the researchers can show association — the more the participants view themselves as rational, the less money they donate; the more they view themselves as reasonable, the more money they donate — they cannot say for sure what motivation is driving people who opt for reasonableness over rationality. We need a lot more research before we can draw any sweeping conclusions.

But it’s worth noting that this study is part of a larger trend: Grossmann and Crockett aren’t the only ones currently challenging our inherited picture of rationality. The past year alone saw the publication of three books by three professors who question what role rationality can and should play in our lives: Can Science Make Sense of Life? by Sheila Jasanoff, Irrationality by Justin E.H. Smith, and The Territories of Human Reason by Alister E. McGrath.

All three books suggest rationality is not a single unchanging thing; it has a history, and it takes different forms in different times, cultures, and situations. And all three ask: What would it look like if we challenge today’s prevailing notion of rationality and put it in its proper place by recognizing that there are actually multiple rationalities, each adapted to the tasks of a particular domain?

That question, it seems, is gaining traction.

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