Research Projects

Written by: Dr. Blake Morton

Some of you may have seen or heard about our capuchin and squirrel monkeys participating in a special type of problem-solving task, which we’ve affectionately dubbed “the cup game”. This task is designed to measure object permanence, which is a fancy term psychologists’ use to describe why an individual knows that when an object or person goes out of sight, that object/person still exists (i.e. it hasn’t fallen off the face of the earth!). In humans, this mental ability has fully developed by around two years of age, which is why children younger than this typically find the “peek-a-boo!” game hilarious: when you cover your face with your hands, children who have not yet developed object permanence think you’ve disappeared, which is why they act surprised as you “magically” reappear and say “peek-a-boo!” with a grin. It’s a classic stage in child cognitive development.

We’ve known for quite some time that monkeys and other animals like dogs and birds have this ability too. Not surprisingly, this ability should exist in many different kinds of animals where, for example, individuals foraging in trees might benefit from understanding that hidden food items are behind branches and leaves, or that predators concealed by tall grass are still lurking nearby!

We use the cup game at Living Links to train new researchers who come to work with our monkeys. The task is fun and easy to administer, and it gives the monkeys and new researchers an opportunity to get to know one another! Have a look at one of our squirrel and capuchin monkeys participating in the cup game below.

Squirrel Monkeys Cup Game Video

Capuchin Monkeys Cup Game Video

As you can see in the videos, monkeys must choose between two different cups. One cup has a hidden food reward underneath it, the other cup does not. Each monkey gets the chance to play the game twice a day, once in the morning and then again in the afternoon. Within each of these sessions, monkeys can get up to ten food rewards if they choose the correct cup every time. The monkeys’ behaviour suggests that they possess object permanence because they always reach for the cup containing the hidden food reward, even when the position of each cup has been switched. A simple task, but it is clear that object permanence exists in these species – just like us!

Written by: Kirsty-Marie Moran

Have you ever involuntarily screamed at a scary movie? Ever wondered why you couldn’t control it? Well, the underlying cause of this spontaneous vocalisation that draws all attention to you in that split second is emotion. This lack of control over some of our emotions is not unique to humans, we also share this with other species such as nonhuman primates. Primates may not scream at a scary movie when scared or startled but they do produce an alarm call when a threat is near by, communicating this message to their group mates. 

However, emotions do not always result in involuntary vocalisations, they can somewhat be controlled and used to your advantage, for instance, as a child if you cry because you did not get what you wanted and your parents give in then you learn to use those ‘crocodile tears’ to get what you want. This deceiving behaviour is something that primates such as chimpanzees also do in certain contexts

When competing for food, chimpanzees can produce a false alarm call, tricking others into thinking a threat is nearby which gives the calling chimpanzee an opening to go get food first. Up until recently, this deceptive behaviour has been limited to species with high cognitive abilities. However, recent evidence suggesting high cognitive abilities are not necessary for this deceptive behaviour has led to the belief that maybe smaller primates, such as brown tufted capuchins can also deceive their fellows, much like chimpanzees do.

This led to an important research question, ‘can Capuchins use alarm calls to deceive conspecifics or are these calls a product of involuntary emotion?’

One of our researchers at Living Links alongside researchers from German, Italian, and UK universities set out to answer this question by focusing on the occurrence of anxious behaviours i.e. scratching when these false alarm calls were produced by capuchins.

The researchers placed banana pieces on wooden platforms (figure 1) to stimulate food competition and elicit the ‘deceptive’ calls in wild black Capuchins at Iguazu National Park, Argentina. It was predicted that if anxiety drove the false alarm calls, then anxious behaviours and ‘deceptive’ alarm calls would happen together. Additionally, brown tufted capuchins at the Institute of Cognitive Sciences and Technologies in Italy were observed to check if their alarm calls and anxiety more generally occurred at the same time.

Figure 1.

During the platform experiments in the wild, it was found that those who gave alarm calls displayed a lower level of anxiety. Whilst those who gave alarm calls in captivity displayed higher levels of anxiety. These findings suggest that anxiety was a reliable indicator of predator alarm calls, but that anxiety alone does not fully explain this phenomenon.

Overall, it was concluded that anxiety is necessary for the call to be produced, but some form of intentional control ultimately decided whether they would call or not. This suggests that it is unlikely these monkeys intentionally trick their group mates, but that they are driven by emotion and possibly associative learning.

Kean, D., Tiddi, B., Fahy, M., Heistermann, M., Schino, G., & Wheeler, B. C. (2017). Feeling anxious? The mechanisms of vocal deception in tufted capuchin monkeys. Animal Behaviour, 130, 37-46. doi:10.1016/j.anbehav.2017.06.008