“Busy Boards” as primate enrichment

Hello, my name is Nailah and I am an Experienced Animal Keeper on the Budongo/Living Links section at RZSS Edinburgh Zoo. As a keeper looking after the research monkeys at Living Links, part of our role is helping to enhance animal welfare by proving stimulating and exciting enrichment for the monkey groups. Usually this is food-based enrichment hidden in objects, often challenging for the monkeys to extract so that they have to use their minds to get the food out! However, other types of enrichment can be made for the monkeys that is not focused on food- I have been working on designing and creating a new enrichment for the Living Links squirrel monkeys called a Busy Board

Nailah busy creating her boards from mixed materials!

For some time now, busy boards have been designed and implemented with human toddlers in mind. The idea behind a busy board is for children to be exposed to a host of different textures, noises, colours and unusual items all part of one item to play with. Even though they were initially intended for children, the advantages mentioned below are also beneficial to non-human primates. I wanted to recreate an interactive activity board that I had previously made for other species of primates for the monkeys at Living Links. I attached various items on this board that food can be hidden in for the monkeys, such as square knots made out of old firehose, pieces of hose pipe, brush heads and even old socks!

Pictured here is the West group of squirrel monkeys having their first look at their new busy board!

So what are the benefits of a busy board?

  • It may facilitate the development of brain neurons. Sensory play aids in the physical growth of the brain and strengthens the pathways between neurons in the brain
  • Sensory play is closely linked to cognitive development, problem-solving abilities, and fine and gross motor skills
  • Sensory play enhances an individual’s memory through practice. By interacting with different textures, tastes, and smells, primates use their senses to strengthen and build their cognitive and motor memories
  • Every time a primate touches an object that is cold, sticky, wet, or has different textures, they are expanding on their prior knowledge of these properties.
  • Through sensory play, primates can associate new objects to similar ones they have already encountered by using their brain’s ability to recognise characteristics in objects and sensations. We have had researchers test this in our monkeys in past research projects!
Squirrel monkeys in their outdoor enclosure exploring new objects in a past research study.

Designing experimental apparatus for monkeys!

Written by Dr Emma McEwen

In many of the experiments at Living Links we use physical apparatuses that the monkeys can interact with, like different puzzle boxes, enrichment containers, dispenser shoots or objects for them to explore. When we design these new apparatuses, there are lots of different considerations we have to be aware of, and its often a collaborative effort between the researcher, the keeper team, and our Psychology & Neuroscience workshop to come up with the best solutions!

Our primary concern is always the safety of the monkeys, and of the experimenters. We always have to consider that a material is safe for the monkeys to touch in a way that they can’t get hurt, is non-toxic and easily cleaned so that it’s safe for their food rewards to touch, and something they can’t pull into their enclosure and do damage with.

Some design process stages including workshop cutting of materials, sketches and mock up protocol

Secondly, it has to be durable – capuchin monkeys can be stronger that you might think! We always have to consider the durability of the materials we use, making sure they can’t be easily torn or snapped, and that the monkeys can’t knock them off the experimenter’s table.

It also has to be enjoyable – we always want our research sessions to be enjoyable experiences and only positively reinforce behaviour. This includes only using materials and apparatuses that the capuchins enjoy interacting with. Sometimes, it can be difficult to predict whether they will enjoy touching certain materials. For this reason, we sometimes run some taster sessions, called pilot sessions, to offer the monkeys a chance to interact with a material or part of an apparatus before we build the finished product.

Two types of flap material (green plastic and black silicone) and a monkey reaching into the flap box for a reward!

For example, myself and my collaborator Andreea Miscov are currently testing two types of material to be used as potential ‘flaps’ for a grid box the monkeys will need to search for food rewards in, as part of a memory experiment. One is a silicone material and the other a harder plastic material. There are often individual differences between monkeys, and while some of the monkeys have no problem touching the silicone material, others have not wanted to! On the other hand the plastic material seems preferred from pilot testing so far. It can be important that there are no major differences between how the monkeys interact with apparatus, especially with experiments looking at time measures (a monkey less keen to touch an area of the apparatus will take longer to get their food reward!).

Video example showing durability test, prototype flap box and piloting with the monkeys!

Last but not least, it must be practical – for the designs of our experiments, we need our apparatuses to function in particular ways such as hiding food, sliding things into other things, moving in certain ways, or having certain weights. It can sometimes take us lots of time and trips to hardware shops to browse different materials and find the one that functions or moves in the exact way we’ve dreamed of when designing the experiment!

It can be very challenging to find something that fits all these criteria, but it’s a fun problem to solve!

Squirrel Monkey Training at Living Links

Written by Kenna Valles, Keeper, RZSS Edinburgh Zoo

Training in zoos provides several benefits to the animals and keepers. Training helps to keep animals both physically and mentally stimulated, while building a positive relationship between the keepers and animals, increasing the trust and communication between the two and encouraging animals to voluntarily participate in veterinary and husbandry procedures. This both builds the animal’s confidence and reduces their stress levels during these necessary events.

Figure 1: Squirrel monkeys playing in their enclosure

Just like for your pets at home, veterinary procedures in particular can be very stressful for monkeys; they often have to be separated from their group in a smaller area of the enclosure, sometimes physically restrained and handled by the keepers, without an understanding of why. However, to keep our animals healthy, these procedures are necessary to carry out regularly. Specifically training animals for veterinary purposes decreases an animal’s fear towards these procedures, allowing them to cooperate in their veterinary care and associate the procedure with a positive outcome by giving them a reward for participating.

The training performed at Living Links by keepers uses exclusively positive reinforcement techniques. This means that the training is voluntary to participate in and the monkeys are given a valuable reward, such as a food item, for performing a desired behaviour, without any punishment for not performing a behaviour. It is also perfectly acceptable for an animal to choose not to engage in training and their daily routine will continue as normal. Our research activities followed a similar training strategy, with the monkeys developing over the years a strong positive association with our research cubicles, the fun cognitively enriching games, and very tasty food rewards! Monkeys voluntarily come into the cubicles to take part as they find the experience so positively rewarding, and it’s this that keeps them returning each day for research.

Figure 2: Dominant male Boa from the ‘East’ squirrel monkey group taking part in scale training

The keepers have been training the monkeys to have this positive association with various veterinary procedures, such as voluntarily sitting on a weighing scale to check body weight (one important indicator of overall health) and entering an area of their enclosure called the ‘holding area’ which is used for veterinary checks and procedures.

To encourage the monkeys to start coming into the holding area and build a positive association with it, keepers rewarded each monkey for coming in by giving them a raisin, a highly valued food reward. When the training first started, the “West” monkeys were very nervous coming into the holding area; only around eight monkeys would come in for a raisin and they would then immediately run back out again. However over several training sessions, the monkeys started to become more confident and trusting of coming into the holding area and soon all 16 “West” monkeys were coming in for raisins! They also became more comfortable staying in the holding area for longer periods of time and now most monkeys will stay there eating for several minutes before leaving.

Figure 3: Keeper Kenna Valles training the squirrel monkeys in the holding area

Prior to this training, when the monkeys were closed in the holding area for procedures, they would be visibly stressed and huddle in a large group in a corner. During the annual vaccinations a year ago, only one ‘West’ squirrel monkeys voluntarily entered the holding area, but this year, after all the hard work with training, all 16 monkeys chose to come in by themselves! In addition to this they were not huddled together and instead were wandering around the holding area and continued to come to the keepers for raisins, suggesting they were significantly more comfortable being in the area than previous years. This is a really great success for both keeper and monkeys!

The “East” squirrel monkey group have also been participating in the same training but have a bit more work to do before they reach the same comfort level as the ‘West’ group, but the keepers are confident they will get there! It is still stressful for the monkeys when the actual procedures are carried out (i.e. injections, being weighed) but Kenna and the keeping team hope to work on training them for these procedures as well, and hopefully with enough training, the monkeys (both our squirrel monkeys and our capuchin monkeys) will eventually be comfortable participating in any veterinary procedure.

New Look Living Links!

Some of our regular visitors may have noticed that Living Links has recently undergone a change in appearance- after 15 years it felt time for a refresh! Led by Research Fellow Anna Redly, Director Professor Amanda Seed and RZSS Interpretation officer Krystyna Keir, the RZSS and University of St Andrews teams have worked closely together to design and implement a fresh, fun and colourful new look to Living Links.

While the work is ongoing and covers several phases, visitors can already enjoy the benefits of the new look Living Links so far! New flags lead the way up the walkways to Living Links, highlighting some of the similarities between us and non-human primates; problem solving, learning, curiosity, playfulness. The different careers supporting the running of Living Links, from keepers to researchers to technicians (and YOU!), are highlighted when you first reach the outer balconies, and will be a feature we focus on in the new Living Links theme.

Our bright new fun colour scheme can be seen throughout the building, inside and out. In front of the windows of the monkeys indoor enclosures we have spinning cubes and panels for visitors to meet some of our monkey faces, learn a bit about them and try to ID them through the window! These have proved extremely popular with children, so much so that we had to install quieter spin systems as the constant use of them was slightly disturbing the monkeys during research!

Outside there are information flaps on monkey behaviour, the ever popular primate family tree with linked information, and soon we will have some behaviour spotting panels and QR links to online monkey ID guides. We will have students running occasional citizen science research from here, asking for your help with one of our long running welfare studies, and we hope this popular task will run more regularly in 2024.

Exiting the exhibit on either side, the flags display a ‘did you spot us…’ examples of behaviours you may see from the monkeys at Living Links- and if you didn’t see it on this visit, keep an eye out next time you are at Edinburgh Zoo!

There are a number of new features still to come later this month, including a ‘join the team’ face cut out board and a special ‘Living Links through time’ highlighting the key people and research themes that have featured at Living Links over the past 15 years. We will also be gradually developing interactive citizen science games for a large screen that will be part of the Living Links timeline, highlighting the importance of getting YOU involved in future research!

There is room for further development with visitor feedback, so we would love to hear from you if you have any particular ideas of what you would like to see or do at Living Links and if you would be interested in being more involved with everyday science! Contact us at livinglinks@st-andrews.ac.uk with your input or join our newsletter to be kept up-to-date!

Do you want to be a scientist?

This month, Living Links is trialing a new Citizen Science game, inviting visitors to participate in some of the exciting research that happens here. Read on to find out more about Citizen Science and how the game works… 

As a research centre, one of our primary goals at Living Links is increasing public engagement with science. That’s why we are launching ‘Living Together’, a new Citizen Science game that allows visitors to collect and classify real life scientific data for our longstanding project about monkey welfare and enclosure use. 

“Citizen Science”, or “Community Science”, is a practice that focuses on advancing knowledge through research done by, for, and with members of the public. It aims to foster a large scientific community as the intersection between public engagement, education, and scientific enquiry. Citizen science projects are great opportunities for volunteers to collect and classify data, improving their awareness of the scientific process and opening avenues for exploration and curiosity of the field.  

The game begins by instructing the participants through various phases of ‘Citizen Scientist Training’. This includes a manual of the different monkey species here, the 5 different zones of the enclosure, and a variety of monkey counting freeze frames where visitors will be challenged to use their keen scientific eye to spot monkeys in each zone (Figure 1).

Figure 1: The different zones of the enclosure.

Following our Training, our newly fledged scientists note down in real time how many capuchins and squirrel monkeys are present in each of the 5 zones. The data and feedback collected from this trial phase will help us improve the final version of the game, in which this extensive numerical data will be analysed by our researchers. This data will reveal where each species prefers to spend time throughout the day, providing researchers and keepers with the knowledge needed to improve the welfare, enrichment, and habitat of these primates. 

We hope that this game can help visitors to gain a newfound connection with research, helping them to feel empowered and engaged with science. If this sounds interesting to you, we hope you stop by!

Written by: Emma Hearn

Serious Fun at Living Links!

Back in April, Living Links hosted an exciting Primate Pop-Up as part of the Edinburgh International Science Festival. Read on to hear about the importance of play, and how zoo visitors took part in an experiment investigating how monkeys learn through play.

Learning through Play

Play is a big part of human life, especially in childhood. It is also a behaviour found in many other animal species. The fact that play is found across the animal kingdom suggests that it must be a valuable behaviour for survival: if it were not advantageous in some way, it would not have evolved. So, the question is – why do we play, if not just for fun?

Right about now you may be wondering what exactly play is. This is a good question – one that comparative researchers have been struggling to answer for years, as common definitions of play tend to be human-centred. Graham and Burghardt (2010) developed a set of criteria that can be used to identify play in any animal species. Play behaviour (1) has no obvious purpose; (2) is enjoyable, rewarding, or spontaneous; (3) is different from day-to-day behaviours (for example, play fighting is more exaggerated than real fighting); (4) is done repeatedly; and (5) is done when relaxed.

Research at Living Links is exploring the idea that that one of the biggest values of play is that it helps us to learn. Children will play when there is something to find out – when they are curious. In a 2011 experiment, researchers gave children a toy that lit up and played music only when specific beads were placed on it. Children tested each possibility in turn, and if two beads were stuck together, they would turn the beads on their ends to try them out one at a time. This behaviour is very similar to how scientists devise experiments! Just through exploratory play, the children were able to learn and remember how the music box worked.

Figure 1: The Living Links monkeys investigating openable versus un-openable objects.

Learning Through Play at the Primate Pop-Up

Animals also like to play around with objects: look at the Living Links monkeys investigating objects that are openable versus un-openable (Figure 1). They played around with the objects in various ways: hitting them and banging them, spinning them around and even roly-polying with them! When they were later given the chance to come into the research rooms, then knew which objects were easy to open and which were difficult. However, even monkeys that did not have a chance to play were pretty good at choosing the right object, so we’ll need to make the task harder in the future!

At the Primate Pop-Up Event, we wanted to observe learning in action, by giving the Living Links monkeys an exciting new resource: crackers! The crackers either contained a jackpot (high value trail mix) or some basic vegetables. We wanted to see if the monkeys were able to learn which resource had high value. Visitors to the pop-up helped create these crackers by filling up cardboard tubes with either low value or high value treats, and then wrapping them in paper. The jackpot crackers were wrapped in black paper, and the basic crackers in brown paper. The monkeys were then given the crackers, while the visitors helped keep track of their selection.

Figure 2: The crackers used in the Primate Pop-Up.

At the beginning, the monkeys were actually scared of the jackpot crackers! This is because they were not used to the black paper and were suspicious of the novelty. So early on in the afternoon, monkeys only chose the basic crackers. However, they eventually decided to explore the black crackers, leading to an even split of choices between the two cracker types. When the same experiment was carried out on the second day of the event, there was a clear preference for the black crackers. This suggests that the monkeys learned which resource had a higher value, just through playing with them!

The results of the Primate Pop-Up experiment showed just how quickly monkeys engage with their environment and learn about it.  We also spent time with the children that visited on the day talking about a future experiment in which we could look at how monkeys learn even when there isn’t any feedback (like food rewards). You can see some of their suggestions in figure 3.

Playing can be a way of conducting informal science experiments, by trying out new behaviours and manipulations and seeing what happens. This helps build up new skills, like tool use and problem-solving. Though traditionally we might think of play as without a real purpose, the research continues to prove this idea wrong – it seems that play is some serious fun!

Figure 3: Some of the kids’ suggestions for future experiments investigating learning through play.



First Impressions- a research intern’s view

Written by: Wilson Chen

Hello, and welcome to the Living Links Blog! My name is Wilson, I am a second-year psychology student at the University of St Andrews. I am currently working in a public engagement with research internship at Living Links. I was interested in an internship at Living Links because I wanted to learn more about the role of monkeys in the study of behaviour and cognition. Moreover, I believe that bridging the gap between psychology research at Living Links and the visitors at Edinburgh Zoo is a meaningful endeavour that can promote and educate the public about psychology as a scientific subject.

Starting a new internship in a zoo can be both exciting and nerve-wracking. I may have been looking forward to this opportunity for a long time, but it can be hard to know what to expect when you’re stepping into a new environment with new people and animals. In this blog post, I will talk about my first impression of the centre and share some of my experiences talking to visitors during my first weekend as an intern.

            Originally, I thought the first thing I was likely to notice was the smell. The smell of monkey enclosures can be quite striking, as primates have strong body odour and produce a lot of waste. However, I was pleasantly surprised at how everything is clean and tidy at Living Links. The environment on the main platform (which is where I spend most of my time working) is fantastic. I can get a great view of both the east wing and the west wing enclosures. It can get quite chilly sometimes, especially when the wind picks up, but I am sure the weather will be much more pleasant when spring comes around.

            Whether it’s to see the exotic animals or to learn about wildlife conservation efforts, visitors often come with their own expectations and interests, and it is very apparent that most visitors are very engaged with the experience Living Links has to offer. When I approached visitors about doing a visitor feedback survey, many visitors reacted positively. To be completely honest, I thought I was going to get shut down most of the time, but I was happy to be proven wrong. Visitors of all ages can be seen at Living Links, and we see a lot of families. For the children coming with their parents, this could well be their first time learning about scientific research. The Living Links centre could be a great starting point in children’s engagement with scientific inquiry and the nature of science.

            While walking around the place asking people to fill in surveys about visitor experiences, I get a lot of opportunities to watch the capuchin monkeys go about their day. As I started to observe them, I began seeing a lot of similarities between their behaviour and human behaviour. Capuchins are social animals that form complex relationships and have a wide range of emotions. Watching them interact with each other can be very fascinating and heart-warming. You may also be struck by how intelligent they are, as you observe them playing, using tools, and communicating with each other in sophisticated ways. One thing that stood out to me is the similarity between the dietary habits of capuchin monkeys and human beings and how they do a lot of the same things as humans. They will remove seeds from food like bell peppers and skin from chickpeas (I noticed they are particularly efficient at this one). Compared to larger mammals who are often seen inhaling entire pieces of food at once, capuchin monkeys are more advanced in their methods of dealing with food.

            Perhaps one of the most rewarding aspects of interning at Living Links is the opportunity to build an understanding of the monkeys. Obviously, I am not there yet as I can barely recognise a handful of monkeys. But I hope that over time, I will be able to tell them apart, get to know each individual’s unique personality and preferences, and develop a deep appreciation for the complexity and beauty of their lives.

            I am looking forward to the rest of my internship at Living Links and I am sure this will be an eye-opening experience.

Abstract Knowledge: Uniquely Human?

Written by: Anna Redly

A recent study comparing the abilities of 4- to 5-year-old children and the Living Links capuchins found that only the human children were able to make predictions using abstract knowledge.

Imagine that there are two brown paper bags in front of you. You know that they contain sweets, but not what kind. You reach into the first bag and pull out a handful of four green gobstoppers. You then reach into the second bag and draw out four chocolate buttons. After just taking four sweets from each bag, you can make a reasonable prediction about what kind of sweet you might find if you went in for seconds in either bag: a green gobstopper for the first bag, and a chocolate button from the second bag. This is called a ‘Level 1 Abstraction’. You will also likely arrive at the conclusion that brown paper bags contain sweets of the same kind – this is called a ‘Level 2 Abstraction’. You would only need to take one sweet from a third bag to predict that all the other sweets in the bag will be the same kind.

Abstractions represent generalised information that is common across different situations, like in the sweet example. This ability is central to the way we humans navigate the world, helping us to learn quickly from limited information and make predictions in new situations. The questions that Felsche and colleagues wanted to investigate were how early human children develop this ability and whether it is an ability that we share with other primate species.

To explore this question, Felsche and colleagues designed an experiment with a similar principle to the sweet example. The researcher would sample items from three containers, which contained sticker strips for the children and food for the monkeys. There were two experimental conditions. In one condition, the sampled items supported the idea that items were sorted into containers by their type (e.g., four apple pieces from one container and four raisins from another). In the other condition, sampled items suggested that items were sorted into containers based on size (e.g., four small items of different types from one container and four large items of different types from another). After exposure to one of the two conditions, the participants were then presented with two new containers and an example item from each and were prompted to choose from which container they wanted to receive their next item. 

Diagram 1: Experimental Conditions

In both conditions, the two example items were always a small but high-value item from one container, and a large but low-value item from the other container. The prediction was, that when the children and monkeys were in the type condition, they should choose the next item from the container with the high value example item – so that they can get a high value item too. In the size condition, one high-value sample does not guarantee that the rest of the items in the container will be high-value, as items are sorted into containers based on their size rather than type. If the participants recognised this, they would choose the large and low-value option because no matter which food type will be next, they at least can secure another big item, which is always better than a smaller one.

The researchers found that the capuchins choices of test containers was at random and not influenced by whether they had previously seen that treats are sorted into containers based on their size or their type. This performance suggests that the monkeys did not learn about the abstract rules determining food distribution patterns across containers. The children, however, chose the hidden sample linked to the small high value item more often in the type condition compared to the size condition. This sensitivity to the experimental condition suggests that the children were able to generalise at the second level of abstraction and make predictions accordingly.

The researchers then designed a second experiment, to see if the capuchins were able to form Level 1 Abstractions within this paradigm. In this experiment, like in the sweet example, the monkeys and children were presented with only two containers from which four evidence items were sampled, respectively. Like in experiment 1, there were two experimental conditions (type and size), but this time the choice items were sampled directly from the original containers, so no generalisation to new containers was required.

Again, the capuchins performed at chance level in both conditions, suggesting that they are unable to form Level 1 Abstractions. The children performed above chance in the type condition, but seemingly at random in the size condition. This is interesting, implying that while children can use Level 1 and 2 Abstractions to inform predictions, this ability might depend on the item characteristic they form generalisations about (e.g. type or size). However, the researchers also ran a computational model based on the children’s and monkeys’ preferences. This model suggested that the children’s above chance performance in the type condition could be due to the fact that they simply cared more about their reward’s type than its size.

This study has extended our current knowledge of abstract knowledge formation in non-human species and provided a novel task design that can be altered to learn more about the abilities of different species – both contributing to the investigation of whether humans are indeed unique in our ability to use abstract knowledge.

Want to know more? Click here to read the paper!

What is Living Links? Click here to learn more.

‘The Stork’ Comes to Visit the Living Links Squirrel Monkeys!

Written by: Dr. Blake Morton

We are very excited to announce that over the summer, four of our squirrel monkeys in West Group – Gerda, Jasmine, Orla and Toomi – each gave birth to a brand new beautiful baby, marking the most recent addition to our primate family tree here at the centre. Those of you who visited Living Links over the summer might have noticed these adorable yellow “fur balls” darting around their enclosure (with their mothers not far behind, trying to keep up!). The recent births have given researchers and staff an exciting opportunity to learn more about squirrel monkey behaviour. Here are some interesting facts about squirrel monkey infant development, along with videos of the new babies with their mums (click on the links to play)!

Within the lifetime of a squirrel monkey, which is roughly 25 years in captivity, a female can give birth to as many as 10 or more individuals. Typically, females reach adulthood around the age of 2 ½ years, and become pregnant soon after (usually by the alpha male of their group). After a gestation period of around 147 days, pregnant squirrel monkeys finally give birth to a single baby. Most births take place at night, and labour usually lasts around 1-2 hours.

Two of our mothers – Gerda and Jasmine – are over 15 years old, and are the oldest and most prolific matriarchs of their group. Collectively, these two mums have given birth to an impressive 13 monkeys, or roughly 70% of West Group! Orla and Toomi are 6 and 11 years old, and the daughters of Gerda and Jasmine, respectively. Although less experienced than their mums, with Orla having raised 3 babies so far and Toomi having raised 2, they have their mums there for guidance.

Like human infants, baby squirrel monkeys are born with limited motor coordination which, along with their eyesight, improves over time. As you can see in the following video, during this vulnerable stage of development, the babies learn to move around and explore their environment from the safely of their mums’ backs.


Baby squirrel monkeys initially cling to the stomachs of their mums following birth, which as you can see in the video below, makes it easier for suckling. Eventually, the mother will move the baby to her back, where the baby will cling until the next time it needs to nurse. But don’t worry, baby squirrel monkeys have a strong grip to keep from falling while their mums jump between branches!


After about 2-3 weeks, the babies will start to eat solid food particles that they find on their mother’s fur (that is, if she’s a messy eater!), or, as you can see in the video below, by cheekily stealing food directly from mum’s hand! Baby squirrel monkeys will continue to nurse from their mothers up until about 6 months of age, after which they are completely weaned and learn to find food on their own.


The four new babies seem to be growing quicker by the day. Now that we’re mid-way through November, each baby is showing signs of becoming increasingly independent. They nurse less, and instead eat more solid foods, like fruit, seeds, insects, and vegetables. As you can see in the video, they spend the majority of their time playing, exploring their environment, and climbing branches all by themselves.


Despite their growing independence, at the end of each day, both baby and mum will come back together to curl up and sleep. As you can see in this video, however, mum always keeps a watchful eye to protect her little ‘bundle of joy’. Clearly, a mother’s job is never done!

Tired mums

“Cup Game” Provides Insight into Monkeys’ Understanding of Hidden Objects

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!