Financial gamble? My brain made me do it

Whether it comes to financial planning, extreme sports or dating, some people are willing to take more risks than others.

Researchers have linked several socio-economic and demographic factors with the degree to which people tolerate risk, and age consistently comes up.

When making financial decisions, older people are more likely to pick safe options with secure but smaller payoffs than options that yield higher but uncertain payoffs. In other words, older people tend to avoid financial risks.

Age and other demographic and socio-economic variables, however, are not the only determinants of individual attitudes to risk. With the development of non-invasive techniques to measure brain structure, researchers have also looked for biological links.

Looking at the brain

In a 2014 study, we found the volume of grey matter in one specific brain region (posterior parietal cortex) was linked with young adults’ attitude to risk. Young adults who had less grey matter were less willing to take risks.

A decline in grey matter volume is a natural element of healthy ageing, with parietal regions particularly affected. Generalising this finding, you could say it is the decline in grey matter volume rather than chronological age itself that drives the change in attitudes towards risk as we age.

This is precisely the hypothesis we tested in our recently published paper.

We recruited more than 50 New Yorkers aged 18 to 88 who we asked to choose, in private, between a safe option of receiving a certain US$5 and a lottery that offered a larger, but uncertain, payment up to US$120.

We changed the size of the lottery reward and the likelihood of receiving it to find out exactly how much people need to be paid to take the risk instead of the definite US$5.

We measured the volume of grey matter in their brains using magnetic resonance imaging.

It turns out grey matter volume in the posterior parietal cortex is again linked to attitude to risk. Also, consistently with previous research, older people who took part in our study were more risk averse and picked the lottery less often than younger participants.

But crucially, once we accounted for individual differences in grey matter volume, age was no longer linked with attitude to risk.

Pace of ageing

This result suggests it is the pace at which our brain changes as we age, rather than our age in years that affects our decision making. There may be many reasons some people’s grey matter volume reduces faster than others but we know a lot of it has to do with what we do every day.

Many researchers feel comfortable making the analogy between the brain and muscles – the way we use our brain affects its structure in a similar way that our choice of physical activity affects the shape of our muscles.

At this point, however, we don’t know whether and which “brain exercises” could affect your brain in a way to make you more tolerant to risk, or even if particular exercises could target the posterior parietal cortex.

Link not cause

Our study shows a link between grey matter volume and attitude to risk. To find out if one causes the other, we would need to use more invasive techniques, such as transcranial magnetic stimulation, which temporarily reduces neuronal activity in a localised brain area.

We also have only studied a particular part of the population, healthy adults living in New York. These participants were making decisions between very specific, well-described monetary options. More research is needed to find whether the results hold in the general population and whether we can extend them to the decisions that involve risky health or social outcomes.

It’s encouraging to see there is an overlap in the map of brain regions involved in decision making with a variety of rewards as it suggests our results may at least to some degree extend to how people make decisions other than financial ones.

Agnieszka Tymula receives funding from the Australian Research Council. This research was funded by the National Institute of Health.