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Sometimes, It's Best to Be Irrational

Theoretical psychologists show that when the world is being random, the best option leads to oddly inconsistent preferences.
(Photo: Laura Dahl/Flickr)

(Photo: Laura Dahl/Flickr)

We know people aren't great at making choices, and sometimes the choices we do make are downright weird. (See: politics.) Well, take heart, fellow humans: It's actually pretty common to make odd, irrational decisions—and, according to a new study, it might even be for the best.

"Why humans make irrational choices has puzzled economists and psychologists for decades," write Konstantinos Tsetsos and his colleagues in Proceedings of the National Academy of Sciences—though "irrational" has a special meaning here. To decision scientists, rational preferences are ones with a certain order to them. For example, pretend you thought to yourself yesterday morning, "I prefer Hillary Clinton to Bernie Sanders." Then pretend you thought about Donald Trump, and quickly changed your preference to Sanders. Well, that shows your preferences aren't rational, at least in the classical economics sense: If you really had a well-formed preference for Clinton over Sanders (or vice versa), contemplating Trump shouldn't have changed your opinion.

Irrational preferences may go hand in hand with making better choices overall.

That such irrationalities exist has been well known for a while, and, in the past several decades, a rough understanding of the phenomena has emerged: Basically, our brains are limited, often faulty computers incapable of fully rational decision making, so we make faulty decisions. But, according to Tsetsos and his colleagues, that view is backwards. In fact, they argue, seemingly irrational preferences may be the best thing for us, given our biology.

Here's how the argument goes: We make decisions by accumulating evidence for or against various options—for instance, going to Bali or Berlin for a vacation. Even if the information we absorbed about those spots was perfect and complete—which it's not—it would get corrupted while we process it. Sometimes neurons misfire, signals between brain regions get garbled, and randomness creeps in—what the team calls "late noise." As if that weren't bad enough, the researchers theorize our brains start to ignore information about less appealing options, something they call "selective gating." If early considerations leave Berlin looking cold and dreary, for example, we'd start ignoring new, potentially important information—say, good things to do when it's cold in Berlin—even before we've decided where to go. Not the most rational thing to do.

In previous work, Tsetsos and frequent collaborators Nick Chater and Marius Usher showed that framework could explain irrational preferences like the Clinton-Sanders preference reversal. In their latest paper, the researchers go one step further: The selective gating mechanism, though it produces apparently irrational preferences, actually improves decisions on average. The reason, computer simulations and laboratory experiments showed, is that selective gating compensates for late noise—basically, your brain starts ignoring some information to prevent last-minute neurological misfires from turning into bad choices. In other words, irrational preferences may go hand in hand with making better choices overall.

"This finding calls into question the longstanding argument that humans are irrational because they lack the computational resources" to make good decisions, the researchers write. Instead, irrational preferences may result from the need to make good decisions with an imperfect tool—the brain.


Quick Studies is an award-winning series that sheds light on new research and discoveries that change the way we look at the world.