Thinking fast, slow and different
De Martino arrived in Cambridge last year as the Sir Henry Dale Fellow (Royal Society and Wellcome Trust). His work is underpinned, he says, by a deep desire to get away from “black and white thinking” and dig deeper into the complexities of the human mind. It’s why he chose to specialise in neuroeconomics, pioneered by his Wellcome mentor Professor Daniel Kahneman, author of the bestseller Thinking Fast and Slow, and the winner of the Nobel Prize for Economic Sciences in 2002. (“He told me that he never took an economics class in his life,” says De Martino. “It’s pretty cool that you can get the Nobel Memorial Prize for a subject you’ve never studied.”). Kahneman, together with his colleague the late Amos Tversky, were among the first to use empirical evidence to challenge the assumption of rationality dominant in classical economic theory. Their work was pivotal to the birth of neuroeconomics, a new discipline that combines psychology, new imaging technology and economic concepts in order to find new ways of understanding human behaviour. This new, young discipline has not been without its detractors.
“People think it’s all about bits of the brain lighting up,” De Martino says. “But that is a profound misunderstanding of our goals. Finding different areas that light up – that was early neuroimaging, almost like phrenology. But how do the different parts of the brain work together to control complex behaviour? What are the neural dynamics of these computations? That’s what we are interested in. For example, economic theory will tell you that it doesn’t really matter how I frame the question. You should make your decision based on the benefit that you get. But we have studied the neurobiology of nudging – the fact people are incredibly susceptible to frames.” He gives the example of a dieter picking up a 70% fat-free yogurt. “Great, you think, and you buy it. Now, imagine the same snack was advertised as 30% full fat. It’s exactly the same percentage of fat. You understand that. But you’re probably not going to buy it. Sometimes what you’re saying doesn’t matter – it’s the context around it. We are now starting to understand how this contextual information is represented by the brain and how it shapes our daily choice.”
The strangeness of confidence
De Martino’s team are now investigating another less than rational human trait: confidence. It is a strange concept, he says, and one that everyone believes they know how to define but is a lot more complex when you look below the surface. De Martino is investigating its link with uncertainty, combining complex brain imaging technology with Bayesian probability – the idea, derived from the work of Thomas Bayes, the 18th-century Presbyterian minister with a passion for mathematics, that when you make a decision, you always have a prior belief. This, in turn, is shaped by sensory evidence, creating a ‘posterior’ belief.
What really matters in that process, he says, is the uncertainty. “If your prior belief is very uncertain, any information I get from you is going to drive that belief. But if you have a very strong prejudice, you need to give me way more information to change my prior belief. For example, I am Italian. I am very precise and I am always punctual. But people have a prior belief that Italians are always late. So people will want way more evidence to change their prior belief because they have much more certainty about that prior belief.”
Research is still in its early stages, but De Martino is confident – in its most basic sense – that exciting ideas will emerge. “What I want is to build a model of the human brain that shows how we really are,” he says. “Not an ideal standard of rationality.”