"Humans are inconsistent in their behaviour, often making different choices under identical conditions," that economic theory has been unable to explain. People can make one decision one day, and the opposite decision another day.
Key Takeaway
Inconsistent behaviour and impulsivity may be due to low activity in brain areas rich in dopaminergic neurons. "While risk preferences are thought of as personality traits determined partly by genetic variation, we show that the expression of risk preferences reflects in part individual susceptibility to endogenous [brain] fluctuations."
Researchers from University College London wanted to know whether resting state brain activity has something to do with this. In the resting state, brain activity doesn't stop but continues to fluctuate. And they were particularly interested in the substantia nigra (SN) and the ventral tegmental area (VTA), areas that contain most of the dopaminergic neurons.
The researchers put 43 participants into the MRI scanner. When the participants were at rest, they were asked to choose between two options: A safe option (￡2.8 guaranteed) and a risky option (￡0 or ￡6; 0 ￡0 or￡9; ￡0 or ￡12, with equal probability of getting ￡0 or the stated sum of money). "If they chose the risky option and lost, they would receive nothing."
Low activity in certain brain areas led to increased risk taking
The researchers found that the resting brain activity in the SN and VTA, just before the options were presented to them, was revealing: When the activity was low, the participants chose the risky option; when the activity was high, they chose the safe option.
Image by Chew et al. used under CC BY 4.0 / Cropped from original. Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6744888/
You can see that above in panel A, where low brain activity in the SN/VTA (shown in orange) led to more risky choices. High brain activity in these areas (shown in yellow) led to less risky choices. What's especially remarkable was that this effect of greater risk taking for low than high activity was consistent across all participants. You can see that in panel B above where the dots cluster around the sloped line.
"The effect size is comparable to other known factors affecting risk-taking behaviour, such as drugs that influence the neurotransmitter dopamine that are routinely taken by people with Parkinson's disease. The effect is also similar to ageing; being young is associated with greater risk-taking compared to being elderly."
Low SN/VTA activity may mean more, not less, dopamine
These results don't mean that low SN/VTA activity refers to low dopamine levels. Rather, the authors believe that low SN/VTA activity means that there are fewer dopamine receptors in these areas. This would mean that more, rather than less, dopamine in the system leads to riskier choices. Other research has linked diminished dopamine receptors with trait impulsivity. We had seen in the Masterclass on Willpower and Motivation that dopamine is released when we expect a reward. And this could lead to greater risk taking.
"Our brains may have evolved to have spontaneous fluctuations in a key brain area for decision making because it makes us more unpredictable and better able to cope with a changing world." The researchers plan to continue their investigation into the effects of variation in background brain activity and the results could eventually inform treatment approaches, such as for pathological gambling .
Conclusion
The authors conclude: "Our key finding is that variability in higher-order cognition can emerge out of a neurophysiologically well-defined process. While risk preferences are thought of as personality traits determined partly by genetic variation, we show that the expression of risk preferences reflects in part individual susceptibility to endogenous [brain] fluctuations."
This study points to the need to take time before making an important decision. If we wait just a few minutes, it might lead to a different decision. Perhaps people choose risky behaviour as a way to increase dopamine levels.
References:
Chew, B., Hauser, T., Papoutsi, M., Magerkurth, J., Dolan, R., & Rutledge, R. (2019). Endogenous fluctuations in the dopaminergic midbrain drive behavioral choice variability. Proceedings of the National Academy of Sciences, 201900872. doi:10.1073/pnas.1900872116
Photo by Kamil Pietrzak on Unsplash