Apes can make irrational choices like humans

In a gambling setting, apes deploy a similar economic strategy that humans do...
13 January 2023

Interview with 

Penelope Lacombe, Université de Neuchâtel


orangutan ape


Gambling is something that most of us do in our daily lives. This doesn’t necessarily refer to monetary gambling, although 44% of adults in the UK have done so in the last 4 weeks, but deciding to cross a busy road or deciding you know better than the satnav becomes a form of gambling when one decides to take a risk. This sort of economic strategy, measuring the cost of the risk against the benefit of the reward, is very human. But is it exclusive to humans? Will Tingle reports…

Will - Humans are generally speaking risk averse. Given the choice, we are more likely to pick a safe option than a risky one. If someone was given a choice between a set amount of money or a mystery amount, that could just as likely be double or nothing at all, the majority of people would stick with what they had. But is this an inherently human trait or something that we share with our relatives? Penelope Lacombe, from the Université de Neuchâtel wanted to find out. But first the question was - how do you get the ape subjects to play along?

Penelope - Food. Food, either fruit like a grape or vegetables like carrots or beetroots.

Will - So, once the gorillas and orangutans were on board with the game, did they stick or twist?

Penelope - In this kind of experiment, yes. Like humans, they preferred a safe option. They did not want to take a chance, so they preferred the stable and safe pieces of food.

Will - So apes do match human's risk averseness in this particular setup. However, there are instances in which the framing of a situation makes people more prone to take a risk. If there's a tray with multiple cups, one of which has a larger reward under it, then the average person is more likely to risk their safe option. And it appears our primate relatives are the same.

Penelope - In this experiment, the apes were risk prone. They wanted to bet. So in the other experiments there was not a mystery box, it was a tray of boxes and the apes knew that under one of these boxes there was the reward. So they knew the reward and they knew the probability to gain it. For instance, there were two risky cups and they knew that there were eight pieces of grapes under one of the two. So they also had a 50% chance of winning. But it was not presented exactly in the same way. And in this case, they wanted to bet.

Will -
The second setup shows that apes like humans can make irrational decisions based on their previous biases. Decision making is context dependent and, once they know the rewards are high, they are more likely to try and take a risk. So why is this?

Penelope - There are different hypotheses. The first one is that they wanted to explore more cups to explore and that could drive an exploration bias. They are curious, so they want to understand what's going on. So if there are more cups, maybe they will want to explore more. That is one of the hypothesis we had. Another one is that, in this case, they knew that the reward was somewhere, so this could also make them more impulsive. They knew that there was food under one of the cups, so I have to try, I have to try it and find it. Whereas with the mystery cup, maybe there is nothing under it. So that could drive less betting behaviour.

Will - The knowledge that there is a definite reward somewhere out there was enough to drive these apes to take a risk more often than if the existence of a reward wasn't certain. And as with all gambling, part of the bet is the regret.

Penelope - Apes are a sore loser that do like to lose. And well that was one aspect of the research that we wanted to test. Are they more annoyed when they're losing food in either one of the experiments? That could also give information that could be interesting. So we filmed them to see how they react to losing a bet, and very often they try to whip us with the sticks that they had in their enclosure, or spit on us, or they just left and quit experiments. That was something that we observed frequently during the experiments. And it's also interesting to see that they are very committed in the bedding process. They do not like to lose and they express a whole variety of behaviour that show that.

Will - So there you are. Gambling - it's no monkey business.


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