The cookie jar sits right next to the fruit bowl - which do you choose? Our willpower is regularly tested. A study published this week watches participants battle with self-control in real time.

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A new study gains insight into human willpower, or lack thereof.

For many of us, there is a gulf between what we know we should eat and what we want to eat. In fact, perhaps tens of times per day, our willpower is called upon to make healthful dietary choices. But some people are better at winning this battle than others.

Psychologists are interested to know what is going on in those vital seconds between viewing the "fruit or brownie" conundrum and acting upon it. They want to know what separates the strong-willed from the weak-willed.

A recent study, conducted by Paul Stillman and his team at the Ohio State University in Columbus, takes a peek at what happens in the time between seeing food and making a decision. The intriguing results are published this week in the journal Psychological Science.

Apple or cookie?

In the study, participants were placed in front of a computer screen. Once they clicked "Start," a cursor appeared at the bottom of the screen, and, at the top left and top right of the screen, there appeared a healthful and an unhealthful snack choice.

The participants were told to choose, as quickly as possible, which of the food items would most help them to "meet their health and fitness goals." So, even if they were tempted by a piece of cake, they knew the "correct" answer.

Before the trial began, the group was informed that, at the end, they would receive one of the foods that they chose in the experiment. In reality, once the trial had finished, they were all given the option of an apple or a candy bar.

The team found that some people initially moved the cursor toward the unhealthful snack, even though they eventually clicked on the healthful choice. These individuals, when offered the food choice at the end, were more likely to opt for the candy bar.

In other words, in the small amount of time taken to decide on which food to choose, those with lower levels of self-control were given away by their subtle hand movements.

"Our hand movements reveal the process of exercising self-control. You can see the struggle as it happens. For those with low self-control, the temptation is actually drawing their hand closer to the less healthy choice."

Paul Stillman

Conversely, participants whose cursor movements honed in on the correct food choice without deviating toward the delicious treat had a higher level of self-control, choosing to opt for the apple at the end of the study. This indicates that they experienced less internal conflict.

As Stillman explains, "The more they were pulled toward the temptation on the computer screen, the more they actually chose the temptations and failed at self-control."

Charting self-control

The team carried out another two studies, both of which produced similar results. In one, college students were given a choice: $25 today or $45 in 180 days. Once again, the cursor trajectories of people with higher self-control were significantly different from those with lower levels of self-control.

The findings may help in a debate that is ongoing in this field of study. Some psychologists believe that there are two competing systems in the brain: one that is impulsive, and a second that works to override the impulse.

The cursor movements measured in this study go against this theory. If there were two systems, Stillman argues, there would be an initial, direct line from the bottom of the screen toward the unhealthful choice, then "an abrupt change in direction" as the willpower system kicks in, shifting the cursor toward the good food choice.

What the researchers actually saw was a curve, as if the good and bad outcomes were competing right from the start. As Stillman explains, "Our results suggest a more dynamical process in which the healthy and unhealthy choices are competing from the very beginning in our brains, and there isn't an abrupt change in thinking. That's why we get these curved trajectories."

The researchers hope that these findings will give new insight into willpower and decision-making, as well as provide a new methodology to help examine our ability to resist temptation.

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