US researchers studying decision-making have watched in real time how people's hands reveal the struggle they go through when choosing between a long-term goal and a short-term temptation.

In one key experiment, participants were observed choosing between a healthy and an unhealthy food. In each trial, the students clicked a button at the bottom of the screen to start the experiment. Images appeared in the upper-left and upper-right corners of the screen, one a healthy food, such as Brussels sprouts; and the other an unhealthy one, such as a brownie. They were asked to move a cursor from the center to select one of the foods.

Among 81 college students who made 100 decisions, people who moved the cursor closer to the unhealthy treat, even when they ultimately made the healthy choice, later showed less self-control than did those who made a more direct path to the healthy snack.

They were told to choose as quickly as possible which of the two foods would most help them meet their health and fitness goals. So there was a "correct" answer, even if they were tempted by a less healthy treat. 

They were also told, before the experiment began, that they would be given one of the foods they chose. At the end, however, they could freely choose whether they wanted an apple or a candy bar.

Detailed in a paper appearing in the journal Psychological Science, the results showed that those who chose the candy bar at the end of the experiment, namely those with lower self-control, had tended to veer closer to the unhealthy foods on the screen. And for those with higher levels of self-control, the path to the healthy food was more direct, indicating that they experienced less conflict.

"The more they were pulled toward the temptation on the computer screen, the more they actually chose the temptations and failed at self-control," noted Paul Stillman, co-author of the study and postdoctoral researcher in psychology at the Ohio State University, who worked with Melissa Ferguson, professor of psychology, and Danila Medvedev, a former undergraduate student, both from Cornell University, on the project.

When the researchers mapped the trajectories people took with the mouse cursor in the experiment, they observed that most participants did not automatically start directly toward the unhealthy treat before abruptly switching course back to the healthy food.

Rather, the trajectories appear curved, as if both the temptation and goal were competing from the beginning.

Stillman said these results should help lead to a more accurate view of how our cognitive processes unfold to allow us to resist temptation.

(With inputs from Xinhua)