October 18, 2013

Interview Professor Paul Rozin: Why we have to change people's world if we want them to eat better

Retiring this year, but still busy doing research. Inspired by the way musical pieces often start out slow, build up and then climax, he enthusiastically talks about a new project. 'People come up with a summary judgement of how good a meal is. We are looking at the degree to which an ending is important. You put the best things at the end. People like things that rise', he explains a new study.

In December, I am invited to stay at the Centre For Advanced Studies at the Norwegian Academy of Science and Letters. Every year, this centre hosts three parallel research groups organized around a central theme. One theme of this year is 'The ecology of food perception'.  Researchers from Norway and abroad are invited to work together for several months. Paul Rozin is also invited and I visited him during his stay. He is a professor of psychology at the University of Pennsylvania. Paul Rozin is considered to be one of the most influential researchers on human food choice and particularly known for his work on the meaning of disgust.

We talked about working with Brian Wansink ('We have similar attitudes towards things and we are both outliers'), journals' bias to only publish positive results ('That is ridiculous') and pressure to publish or follow a particular model of how to do research. 'The basis question one should ask is how much the contribution adds to understanding', he writes in his 2009 paper in Perspectives on Psychological Sciences. In this paper, Paul Rozin talks about the value of moving from top-down hypothesis testing as dominant research model in many top psychological journals to research approaches that lead to broader generalizations of interesting phenomena. ''What they do is that they find something with a set of experimental parameters and then instead of saying 'Is this real?', 'Can I change the parameters a bit and is it still there?', they go ahead, they analyse it and they go down. That is what a journal wants', he said. Exploring the large picture of a phenomenon is key according to him; 'Even in the lab, you can vary your parameters. A parameter that you think is not critical, often is in real life'.

We went on to talk about obesity ('We plateaued, I think it is because we now drink more bottled water') and interventions that could help people to eat better. When I asked his opinion on Herman and Polivy's argument that not much progress has been made so far in combatting the obesity problem and that it is probably easier to make the case that things are getting worse, he strongly agrees. 'I think they are right. They are very smart people, they worked on this for decades. I have said that but I do not know whether I said it in print. Nothing has been shown to work except maybe bariatric surgery', he said.

This may seem a pessimistic view, but Paul Rozin has clear ideas about possible solutions. He is a believer of the nudge approach: 'I do not think that we can change people. I think we have to change their world. That is what I think has happened in France. Their world is different, the way their food is presented is different. That is why they have half our obesity rates. I cannot proof that, there are too many variables. That is encouraging, that their environment is so different and they are much thinner.'

Paul Rozin, however, is not yet convinced about the long-term potential of nudging: 'There is no question that it works in the short run. What we do not know is whether nudging will work in the long run. We know that it works over a week, but we don't know whether it works over a year, because there may be compensation in various ways. Doing a year's study will involve a lot of investment. You have to get too many people to support you', he said. An interesting perspective of Professor Paul Rozin; a leading expert you should definitely continue to follow.

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