Monkey business! Primates are capable of making rational financial decisions, and just like wealthy humans, the 'wealthier' of our primate relatives are more likely to take risks, a new study has found.
The findings indicate that monkey behaviour is very similar to humans' risk choices, and as a result can provide insight into the evolutionary roots of our behaviour, researchers said.
"Human sensitivity to wealth levels developed before the advent of money. Understanding the biological mechanisms underlying risky behaviours that evolved around satiety may provide unique insights about decision-making and consumption wealth," said researcher Dr Agnieszka Tymula from the University of Sydney's School of Economics.
"We found that after training, monkeys are very rational. Just like humans, monkeys are able to select objectively better options from a menu of choices. If there is an alternative that offers better outcomes in all circumstances, they will go for it.
"The monkeys also seem to share human risk preferences. They were slightly risk averse and we know that humans would behave similarly in these experimental conditions," Tymula said.
Using water intake among the monkeys as a non-pecuniary measure of wealth, researchers examined the level of water the rhesus macaques held internally to differentiate the 'rich' from the 'poor'.
After significant training over 20 days, the macaques were able to engage in visual gambling tasks, associating pie graphs showing various increments to the probability of fluid rewards.
By shifting their gaze from left or the right, the monkeys made their choice between a safe option (of some amount of water for sure) and a risky option that offered a positive (most of the time higher) payoff or nothing, each with 50 per cent chance.
The 'richer' (more satiated) monkeys who possessed a higher blood osmolality were found to be less risk averse and take greater gambles than the 'poorer' less-hydrated subjects, who avoided uncertainty in their decision-making.
Fellow authors of the study included Hiroshi Yamada from the National Center of Neurology and Psychiatry in Tokyo, and Kenway Louie and Paul W Glimcher, from the Centre for Neural Sciences at New York University.
The study was published in the journal Proceedings of the National Academy of Sciences (PNAS).
