Impulse control in great apes: Individual Differences larger than species differences

What is it about?

This study compared individuals of four great ape species—bonobos, chimpanzees, gorillas and orangutans—in their abilities to master reversal learning tasks. * The challenge of the task These tasks involve two options from which the individual can choose one. The difficulty, however, is that they always get the non-chosen option. Given that the reward was highly-preferred additional food in different amounts (e.g., 2 or 4 raisins), the apes had to inhibit their natural impulses to reach for the larger quantity. That is, they had to choose the smaller one instead in order to get the preferred larger amount. For apes, this is quite a challenging task. First, they had to distinguish the quantities. For quantities up to six items, apes can do this quite well. Then they had learn the reversed reward rule: They go the larger amount only if they chose the smaller one. That’s tricky and requires impulse control. * Amount matters The study showed that it was easier for the apes if the difference between the two quantities were smaller. That is, when choosing the wrong option meant loosing a larger amount, this made it harder for apes to learn the reversed reward rule whereas it was easier when not so much was at stake. * Using signs to improve impulse control Moreover, food visibility also played a significant role. The apes performed better when the food items were covered with a coloured lid, as opposed to being directly visible. That is, they learned to use colours as a signs for specific quantities in order to solve the cognitive task and help them at the same time to better control their impulses. * Individual Differences Interestingly, there were pronounced individual differences, regardless of species. That is, in each of the four species (chimpanzees, bonobos, gorillas, and orangutans), some individuals were able to successfully learn to choose the smaller food quantity to receive the larger one, whereas others were not. * No Species Differences Previous research had suggested that chimpanzees underperform in this task because of their more impulsive behaviours compared to other great ape species. This study, however, found no systematic performance differences between the four great ape species. This suggests that the poor performances shown in previous chimpanzee studies may be largely due to individual differences.

Featured Image

Photo by MediaEcke on Unsplash

Photo by MediaEcke on Unsplash

Why is it important?

Impulse control is an important ability especially in socially living species, where conflicting interest must be negotiated in interactions with others. The study shows that, just like in humans, great ape individuals differ in their abilities to control their impulses. Moreover, the apes learned to use colour as a sign to help them manage their impulsive behaviours better. This hints at the importance of sign systems (e.g., language, culture) in dealing with challenging behaviours.