A paper, published in Social Science and Medicine, describes the results of an experiment in which people watched four videos with bowls of jelly beans in front of them. A total of 353 people participated in 35 experimental sessions for the study, which the authors claimed be the first controlled head-to-head analysis of the effects of monetary rewards to encourage and discourage behaviour.
The results suggested financial incentives only worked to discourage consumption, but not to encourage consumption.
During the first video, participants could eat as many sweets as they wished. Before the second video, different groups were instructed to adhere to three different conditions. A control group allowed participants to carry on eating as many sweets as they liked; an ‘eat’ group gave participants £3 at the end of the session if they ate at least 10 sweets; and a ‘don’t eat’ group gave participants £3 if they didn’t eat any sweets. Before the third and fourth videos, all participants were told they could eat as many sweets as they wished. All four video films were selected to be ‘mildly boring’ to encourage people to eat.
The experiment was then repeated two days later, when none of the participants received incentives. Only the incentive to not eat sweets was found to still have an effect at this stage. Participants who had been previously offered a £3 incentive to not eat any jelly beans ate significantly fewer sweets than the participants who had not received an incentive.
One interpretation of these results is that paying people not to eat helps build self-control – but another is that paying people not to eat leads them to believe that not eating sweets is good and that therefore influences their subsequent behaviour.
“Our findings are consistent with the idea that people find negative messages easier to retain than positive ones. Even though we only paid participants not to eat the jelly beans for five minutes, we seem to have primed them with the notion that not eating sweets is something good and this effect was still in play several days later,” said study author and assistant professor of behavioural science at LSE, Matteo Galizzi.
“In the short run we know that incentives work, for example, in helping to motivate people to give up smoking. However, this is the first time that research has directly compared what happens to differently designed health incentives when the incentives are removed. This is an important area of research because, in the real world, most incentives to get people to live healthier lives will not be able to be applied indefinitely.”
The research was undertaken by Professor Paul Dolan and Dr Matteo M Galizzi from LSE and Dr Daniel Navarro-Martinez from Universitat Pompeu Fabra, Barcelona. It was funded by the Centre for the Study of Incentives in Health (CSIH), from an award by the Wellcome Trust Biomedical Ethics Programme.
Source: Social Science and Medicine
2015, 133, 153-158
“Paying People to Eat or Not to Eat? Carryover Effects of Monetary Incentives on Eating Behaviour”
Authors: Paul Dolan, Matteo M. Galizzi, Daniel Navarro-Martinez