Pumping Emotional Iron

You should be feeling really good about yourself right now. You managed to bite your tongue at the office when your hypercritical boss lit into you. So that was good, disciplined and professional. You kept your head down all day, focusing on a tedious but important deadline project that needed your total concentration. And you did all this while not smoking, day three, even though a long drag on a Marlboro sure seemed like a good idea at times. You should be patting yourself on the back.

So why, if you’ve had such a good day, are you about to collapse on the sofa with a quart of Cherry Garcia and watch reruns of Desperate Housewives? When you showed such self-control all day, why indulge all your mindless weaknesses now?

Psychologists have an idea why. Restraint and self-discipline, they say, are hard work—real effort, not unlike weightlifting. And just as you can overtax your biceps or abs, you can also deplete your reserve of emotional control. When life comes at you hard and you persevere, you quite literally use up your potential to do the right thing one more time.

This is where the muscle analogy breaks down a bit. When we overdo it at the gym, we know it; our achy and tired muscles won’t let us forget. But we don’t always know it when we’ve made excessive demands on our self control. We don’t say, hey, I held my temper, worked hard and didn’t smoke—I must be emotionally fatigued. Indeed, we may even be feeling proud or elated, but inside that disciplinary part of our brain, we’re wasted. And we are ripe for all sorts of lapses.

But what if there were a way to monitor self-regulatory expenditure and fatigue—and thus risk for relapse? Two University of Kentucky psychologists speculated that our capacity to control ourselves might be related to heart activity, mostly because there is a lot of overlap between brain structures responsible for behavior and the heart. Suzanne Segerstrom and Lise Solberg Nes decided to keep track of one measure of cardiac regulation called heart rate variability, to see if it might be a reliable indicator of self-discipline.

They ran a two-part experiment. In the first, they tracked volunteers’ heart rate variability while they were either resisting temptation or giving in to it. Resisting temptation for the purposes of the experiment meant eating carrots while passing on a plate of chocolates and cookies; giving in to temptation meant, well, giving in to temptation. As predicted, heart rate variability was higher when volunteers were actively overriding their appetite for sweets, suggesting that the heart is mirroring effortful self-regulation.

In a second part of the experiment, the psychologists had the volunteers take a very difficult cognitive test. The test involved anagrams, some of which were actually impossible, and the idea was to see how persistent the volunteers were when faced with a mental challenge. Those who had exerted themselves earlier by resisting sweets were less determined when it came to the analogies; it appears they used up their stores of self-discipline. Again, as reported in the March issue of Psychological Science, heart activity predicted performance on the test, suggesting it is a good measure of capacity for discipline. In other words, heart rate variability is a good proxy for the mental strength needed to buckle down—or to resist temptation.

This may all be a matter of efficient use of energy. Humans, like all organisms, have a limited supply of fuel and have to make constant trade-offs for survival. When confronted with a threat, for example, the body directs the lion’s share of its available energy to the heart and large muscles, to equip it for either escape or battle. Self-regulation is a bit different in that it often requires mental effort in order not to act. Heart rate variability it an indicator of energy conservation. It’s possible, the psychologists say, that the heart puts on the breaks to reduce its energy demands, making more fuel available for the mental effort needed for calm reflection.

So is all this going to help you go easy on the Cherry Garcia and not bark at your kids? Probably not, at least not right away. You have to wear a cardiac monitor to keep track of your heart rate variability, and that’s not practical for those of us just coping with everyday mental and emotional demands.

But what about an addict struggling through early recovery? In a separate study, alcoholics who were having an easier time with abstinence had higher heart rate variability than did relapsers when exposed to drinking “triggers”—an old watering hole, for example. Most people are capable of overriding self-regulatory fatigue if they know they’re at a vulnerable spot and can actively bolster their motivation to stay the course, so feedback from a heart monitor might be useful. It’s sort of like your heart telling you to be strong.

For more insights into the quirks of human nature, visit "We're Only Human . . ." at www.psychologicalscience.org/onlyhuman.