December 15, 2022 report
Orangutans and gorillas are able to make economically rational decisions, find researchers
Bob Yirka
news contributor
A small team of researchers at the University of Neuchatel's Institute of Biology in Switzerland has found that captive orangutans and gorillas can make economically rational decisions.
In their paper published in the open-access journal PLOS ONE, Penelope Lacombe, Sarah Brocard, Klaus Zuberbühler and Christoph Dahl describe experiments they conducted with orangutans and gorillas housed at Switzerland's Basel Zoo.
Humans are known to make rational decisions based on available evidence—choosing to accept a $100 bill over a $20, for example. But they are also known to make irrational decisions, such as choosing to bet their last $5 at a table in Las Vegas when they have already lost a lot more.
In this new effort, the researchers wondered if apes have similar abilities. To find out, they designed and carried out experiments with captive orangutans and gorillas in which they chose cups concealing treats.
In the first experiment, individual apes were shown two cups, one of which covered a safe option, the other a risky option. Choosing the safe option meant always getting a reward, and always the same reward. Choosing the risky option meant getting a reward, or not getting a reward. But when there was a reward, it was of higher value than the safe reward.
It was determined that both the orangutans and gorillas understood how the experiment worked, and they tended to choose the riskier reward when they were hungrier. Also, the orangutans tended to be more willing to take a risk.
In the second experiment, there was again a safe reward. But this time, the riskier reward involved choosing one of a number of cups in cases where the reward was under only one of the cups and the amount of the reward varied.
In this experiment, both types of apes were only willing to make the risky choice when they knew that the payoff was going to be much more than the safe choice. And when they knew that the reward had grown to a certain size, they always chose the riskier option, even as their chances of getting the reward dwindled.
The researchers suggest the behavior of the apes shows that they are both capable of making economically rational decisions and that they are also capable of making irrational decisions if the stakes grow high enough.
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More information: Penelope Lacombe et al, Rationality and cognitive bias in captive gorillas' and orangutans' economic decision-making, PLOS ONE (2022).
Journal information: PLoS ONE
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