Daniel Lubetzky

Weighing a big decision? Here’s what experts say about when to go with your gut or your rational brain—or some combination of both.
By Elizabeth Bernstein

You have an important decision to make. You’ve done research, made a list of the pros and cons, asked friends and family for advice.
When should you just trust your gut?

Scientists, authors and motivational speakers (plus plenty of moms) have long touted the power of intuition—our mind’s ability to understand something without the need for conscious reasoning. Think of all the recommendations you’ve heard: “Put the problem away and come back to it later.” “Intuition doesn’t lie.” “Sleep on it.”

Many studies support this advice, showing that the decisions we make unconsciously, before our rational mind can get involved, are often better. But not always.

John Bargh, a psychology professor at Yale and director of the ACME (Automaticity in Cognition, Motivation, and Evaluation) Laboratory, has a book coming out this month: “Before You Know It: The Unconscious Reasons We Do What We Do.” Dr. Bargh says that we tend to trust our gut reactions more than our rational ones because they happen so quickly we think they must be true. But there is a problem with this belief, he says: Our emotional states change what our gut tells us. “Say you are angry and tell someone off and think that is the truth,” Dr. Bargh says. “The next day you may be in a very different emotional state and the truth is different.”

Dr. Bargh says that our gut is better at helping us sort out some things, such as whether we are in immediate danger. It can help us quickly identify our preferences. And it’s good at helping us make complex decisions—say, buying a car—when the amount of information and choices can be overwhelming.

But our gut can push us to be impulsive, to drink or smoke when we shouldn’t. It’s a bad idea to rely on it when the consequences of our decision are dangerously high. (You’ll want to make a few conscious calculations before passing that semi-trailer in the driving rain.) And if the outcome of our choice will affect someone else, it’s best not to rely on our gut alone

The connections between the gut and the brain are extremely complex, with multiple pathways of communication: the nervous system, immune system and hormonal system, which facilitate messages from the microbiome—the trillions of micro-organisms that live in our gut and produce molecules similar to the neurotransmitters found in the brain, such as serotonin and dopamine. “The gut is not a blind tube,” says Raphael Kellman, an internist in New York City and author of “The Whole Brain.” “It’s a complex system explicitly interconnected with the brain.”

In a study published in May 2013 in the journal “Social Cognitive and Affective Neuroscience,” researchers at Carnegie Mellon University in Pittsburgh and Northeastern University in Boston performed brain scans on participants who were asked to consider 48 aspects of four different cars, to determine the best choice. Some participants were asked to make an immediate decision, some were allowed to deliberate and some were distracted by a difficult counting task. The researchers found that the same regions of the brain that were activated when the participants were reading about the car choices remained active even when they were distracted. Their unconscious kept working on the problem, even as their conscious mind moved on.

When should you trust your gut?

Consult your gut for complex decisions.

These include important, but not life-or-death, choices such as what car to buy, where to move, which job offer to accept. Your conscious mind will have too much information to sort through, and there may not be one clear choice. For example, there’s a lot to consider when deciding on a new home: neighborhood (Close to work but not as fun? Farther away but nicer?), price, type of home (Condo or house?). Research shows that when people are given four choices of which car to buy or which apartment to rent—with slightly different characteristics to each—and then are distracted from consciously thinking about their decision, they make better choices. “Our conscious mind is not very good at having all these choices going on at once,” says Dr. Bargh. “When you let your mind work on this without paying conscious attention, you make a better decision.”

Make a list and set it aside. Using unconscious and conscious thought to make a decision is often best. And conscious thought should come first. An excellent way to do this is to make a list of the benefits and drawbacks of each choice you could make. We are trained in rational decision-making, so this will satisfy your conscious mind. And sometimes the list will be enough to show you a clear decision.
But if it isn’t, put it away and do something that absorbs your conscious mind. Go for a hike or run, walk on the beach, play chess, practice a musical instrument. (No vegging out in front of the TV; that’s too mind-numbing, experts say.) “Go into yourself without distractions from the outside, and your unconscious will keep working on the problem,” says Emeran Mayer, a gastroenterologist and neuroscientist and the author of “The Mind-Gut Connection” and a professor at UCLA’s David Geffen School of Medicine.

If the stakes are high, try to think rationally even if time is tight. For example, if your gut tells you to jump in front of a train to help someone who just fell on the tracks, that might be worth risking your life. If it’s telling you to jump in front of that train because you dropped your purse, it’s not. Your rational mind, not your gut, will know the difference, Dr. Bargh says.
Pay attention to your state of mind remember that strong emotions can change your intuition. If you’re angry, your gut will give you a different answer than it normally would. Ditto if you’re stressed, in the middle of some kind of competition, or even happy and relaxed. “Remember that what we think is right to do changes from moment to moment,” Dr. Bargh says. So ask yourself if this is the time to listen to your gut.

Eat well. What you put in your gut makes a difference. Refined foods can damage the microbiome in your gut, and this harms the gut’s connections to the brain. “When we eat chemicals—and too much food and too fast—the bacteria in our gut will become deforested and lose their abundancy,” says Dr. Kellman. “And that will affect the transmission of signals to the brain.” He suggests limiting refined foods and eating more vegetables as well as fermented foods that promote healthy bacteria. “Good foods create mental clarity,” Dr. Kellman says.

Stop asking for advice. You can’t listen to your own intuition if it’s drowned out by other people’s opinions, Dr. Mayer says. You’re likely getting their gut reactions, not yours. And you may feel obligated to take their advice. Ask others for guidance if you want. But at a certain point you need to stop and be quiet, so you can hear your own gut.