Uncertainty is very physical sensation. When having to choose between two options, both of which appear equally likely to be right (and wrong!), you are more likely to waver between options, scratch your head or frown. In a recent study, researchers tested three chimpanzees at the Wolfgang Köhler Primate Research Centre on a memory task and found that such “uncertainty behaviors” in chimps, as in humans, increases with the difficulty of the choice.
All chimpanzees in the study went through a brief period of training before attempting the task. During training the chimpanzees learned a sequential list of images. The chimps had to understand that the list of images had an implied hierarchy (A > B > C > D > E) through trial and error. Choosing the images in the right order on a touch screen earned the chimps a reward – a piece of apple or a grape. Chimps were denied the reward when they made a mistake.
After chimps had familiarized themselves with the image hierarchy, their memory was tested using the choice task. During each trial, the chimpanzees were presented with a pair of images from the sequence. This time, they had to choose the image that came earlier in the sequence to receive the reward.
Chimpanzees have amazing spatial memory and are capable of outperforming humans in some memory tests. The fact that they were highly accurate in picking the correct item during these tests came as no surprise. One chimp – ‘Kofi’ picked the right option in more than 95% of trials, ‘Alex’ did so in more than 93% of trials and ‘Jahaga’ in more than 81% of trials.
Interestingly, researchers found that as the choice became more difficult chimps also wavered more between choices. They moved their finger back and forth between the two options, unable to decide – a clear sign of uncertainty. Based on their finding, researchers speculate that chimpanzees experience uncertainty in ways similar to humans.
Subjective experiences in animals are famously hard to study. According to the researchers who conducted the study, this study makes the case that physical signs of emotions can be useful in this regard. However, the researchers acknowledge that “a single study that shows a task-behavior correspondence across two closely related species cannot solve the question of subjective experience”.
Read more about the study by Matthias Allritz, Emma Suvi McEwen, and Josep Call here.
