The Virtues of Hunger

My kitchen cupboards are filled with Trader Joe’s snacks that I bought while shopping on an empty stomach. Chocolate edamame. Pumpkin spiced pumpkin seeds. Kale chips. Lentil chips. Veggie puffs. A medley of pretzels. A collection of trail mixes. You don’t have to be Daniel Kahneman to realize that shopping while hungry is a hazardous habit, since everything looks so damned delicious. Because we are in a so-called “hot” emotional state, we end up making impulsive decisions, buying stuff that we’ll eat on the car ride home and then never again.

And it’s not just the grocery store. Dan Ariely and George Loewenstein famously demonstrated that making male subjects sexually aroused – they showed them an assortment of erotic images – sharply increased their willingness to engage in “morally questionable behavior,” such as “encouraging a date to drink to increase the chance that she would have sex with you.” It also made them less interested in using a condom.

So the science seems clear: hot emotional states are dangerous. They make us eat the marshmallow, forgo the condom, take out the subprime loan. When making a decision, it’s always better to be calm, cool and sated.

Or not.

A new paper by Denise de Ridder, Floor Kroese, Marieke Adriaanse and Catharine Evers at Utrecht University concludes that, for a certain kind of difficult strategic decision, it’s actually better to be hungry.  One possible explanation for this effect is that hunger triggers a “hot” emotional state, making us more dependent on the urges of instinct. We are less reasonable and rational, and that’s a good thing.

The Dutch researchers describe three separate experiments, all of which had relatively small sample sizes. The first experiment features the Iowa Gambling Task (IGT), a game in which subjects are given four separate decks of cards. Each of the cards leads to either a monetary gain or loss of different amounts. The subjects were told to draw from the decks and to make as much money as possible. 

But here’s the catch – not all of the decks are created equal. Two of the decks (A and B) are full of high-risk cards. They contain larger gains ($100), but also some very punishing losses (between $150 and $1250.)  In contrast, decks C and D are relatively conservative. They have smaller payoffs, but also smaller punishments. The end result is a striking contrast in the total value of the decks: while A and B lead to an average negative return of $250 for every ten drawn cards, C and D lead to an average positive return of $250. The question of the IGT is how long it takes players to figure this out.

The novelty of this study was the introduction of the hunger variable. While all of the subjects were told to not eat or drink anything (except water) from 11 PM in the evening until the morning experiment, those in the sated condition were offered a nice breakfast before playing the card game.

The results were surprising, as hungry subjects performed significantly better on the IGT. Among the final sixty trials, those with an empty stomach drew approximately 30 percent more cards from the “advantageous decks” than those who’d just eaten. According to the scientists, the advantage of hunger is that it makes us more sensitive to the urges of emotion. As Antoine Bechara, Antonio Damasio and colleagues demonstrated in their initial studies of the IGT, it only takes about ten cards before the hands of subjects start getting “nervous” – their palms begin to sweat - whenever they reached for the bad decks. (The scientists refer to this as the “pre-hunch” phase.) However, it took about eighty cards before the subjects could explain the nervousness of their hands, and “conceptualize” the differences between the decks. In other words, the feelings generated by the body preceded their conscious decisions. The hand led the mind.

And that’s why hunger might be useful, at least when it comes to the IGT. “We argue that these benefits from being in a hot state result from a greater reliance on emotions that allow for a better recognition of risks that go hand in hand with big rewards,” write de Ridder, et. al. “This would imply that insofar [as] hot states make people more impulsive, impulsivity means that they act swiftly and without explicit deliberation.”

In a follow-up experiment, the Dutch scientists engaged in a more subtle manipulation of hunger. Instead of not feeding subjects, they randomly divided fifty students into two groups. The first group was asked to evaluate a series of snack foods according to their desire to eat it: “To what extent do you feel like having [snack food] at this moment?” The second group, meanwhile, was asked to evaluate the snacks in terms of their price, or whether they seemed cheap or expensive. Once again, those primed to feel hot emotions – the subjects asked to think about their appetites – performed significantly better on the IGT.

The last study investigated a different sort of decision. Instead of playing cards, subjects were given a series of questions about whether they wanted a small reward right away or a larger reward at a later date. (“Would you prefer $27 today, or $50 in 21 days?”) This is known as a delay-discounting task, and it’s a standard tool for measuring the impulsivity of people. Previous work has shown that hot-emotional states lead to less self-control, which is why I bought chocolate edamame at Trader Joe’s and those aroused undergrads were more willing to have unprotected sex. However, the Dutch psychologists found that those students not given breakfast – they were still hungry – were actually better at choosing long-term profit over immediate gratification. Their hot emotional state made them more patient and reasoned, at least when it came to finding the optimal level of delay.

This doesn’t mean that we can walk around the world looking at pornography and expect instant wisdom. Nor will a skipped breakfast turn us into Warren Buffett. However, when we are faced with a difficult and overwhelming decision – one in which our feelings know more than we do - then mental states that makes us more sensitive to our feelings might lead to better choices. In short, it’s not the simple stuff, like shopping in a grocery store, that benefit from our hottest emotions – it’s the hard stuff. It’s drawing from decks of cards we barely understand, or playing chess, or trying to figure out what we most want from life. That's when you want to be listening to the urges of your body. That’s when the hunger helps.

de Ridder, Denise, et al. "Always Gamble on an Empty Stomach: Hunger Is Associated with Advantageous Decision Making." PloS one 9.10 (2014): e111081.