Monetary rewards for eating healthy can pay off both in the pocketbook and in positive psychological factors like internal motivation to eat fruits and vegetables over time, a new study has found.
"Some psychological research and theories suggest that if individuals have external motivations like payment to perform tasks, their internal, or intrinsic motivation can be undermined," said Casey Gardiner from University of Colorado Boulder (CU-Boulder) in the US.
"But in our study the subjects who had been assigned to receive payment for eating fruits and vegetables were still consuming more of them than usual two weeks after the study ended," said Gardiner.
The study - which encouraged daily consumption of fruits and vegetables in exchange for payment - not only showed monetary incentives worked, but that participants increased their internal motivation to eat fruits and vegetables over time.
For the research, 60 adults were randomly assigned to three different groups. Individuals in one group received USD 1 for every serving of fruits and vegetables they reported consuming daily over a three-week period, with the money delivered daily.
People in the second group accrued USD 1 for every serving of fruits and vegetables eaten, with the money delivered in a lump sum at the end of the study.
Participants in the third group reported their fruit and vegetable consumption daily for three weeks with no incentives.
Those who received daily monetary incentives had the greatest increase in their fruit and vegetable consumption, Gardiner said.
"This finding highlights the importance of incentive design in health programmes. Differences in the timing or type of incentive can alter their effectiveness," she said.
"We essentially showed that incentives may be able to help people to 'jumpstart' behaviour changes, but that changes in key psychological factors help people maintain the behaviour when the incentives end," said Gardiner.
Increased fruit and vegetable consumption by participants was associated with more positive attitudes and self efficacy - the confidence in one's own ability to succeed - regarding the consumption of such produce, she said.
