A new study co-authored by Mark Stehr, an associate professor in the School of Economics at the LeBow College of Business, found that paying new gym members as an incentive to work out more often had little impact in changing their exercise habits.

The paper, forthcoming in the Journal of Health Economics, described a study that randomized 836 new members of a private gym into four groups. One received a $30 payment regardless of the number of times they went to the gym in their first six weeks as members; the other three groups received a payment if they attended the gym at least nine times over the first six weeks. The payments were a $30 Amazon gift card, a $60 Amazon gift card or an item from Amazon that was worth $30.

The authors decided to study a group of people who had already engaged in costly actions such as joining a gym and paying membership fees, signaling an intention to use the gym. They found that additional incentives for visits early during a new gym membership were only marginally effective at helping people to increase their exercise, and had no effect on the number of visits after the incentive period.

“People greatly overestimate the amount they will exercise,” Stehr says. “This over-optimism is counterproductive, because it allows people to avoid taking hard steps that are necessary to meet their goals.”