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. 

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.

Guest written by Dr Emily Messer

Monkey medicine, (https://www.youtube.com/watch?v=I5TDlG441gA) a behaviour where our capuchin monkeys (like their wild counterparts) will pick up and rub pungent materials like onions into their fur as a king of ‘monkey self-medication’ has been revisited recently. Funded by the Wellcome Trust, researchers from the University of St Andrews, Dr’s Mark Bowler, Emily Messer, Nicolas Claidière and Professor Andrew Whiten have recently published a new paper (https://www.youtube.com/watch?v=I5TDlG441gA) describing the function of the behaviour and explaining why the monkeys do this socially.

Dr Mark Bowler, one of the researchers on the project has created the following new video clip (https://www.youtube.com/watch?v=EeRsO2Dz8ZU) which follows on the original monkey medicine video to showcase the main results of the study. The researchers discovered that when socially anointing with group mates, the capuchin monkeys were focusing on inaccessible areas of their bodies, such as their upper back, so together they achieve whole body coverage. As a result, if you’re a capuchin monkey, a raw onion is just the thing to rub into your fur, and if there are bits of you that you can’t reach, then one of your group mates is around to help you reach those hard-to-reach areas. And just as when some children in a class have lice it becomes important to treat the whole class to avoid re-infection, so, the research team concluded, the social fur rubbing of the capuchins results in the whole group having their entire bodies protected.

Link: to video about the experiment: https://www.youtube.com/watch?v=EeRsO2Dz8ZU&feature=youtu.be

Link to paper itself: Bowler, M., Messer, E. J. E., Claidière, N., Whiten, A. (2015) Mutual medication in capuchin monkeys – Social anointing improves coverage of topically applied anti-parasite medicines. Scientific Reports 5 http://www.nature.com/articles/srep15030

Written by Suzi Ruby and Lara Wood

 

A recently published study based at Living Links has provided insight into the positive impact that voluntary involvement in individual cubicle research has on captive brown capuchin monkeys (Sapajus apella), whilst also highlighting aspects of research procedures which might be improved.

Given our interest in understanding the evolution of our own behaviour and intelligence, it is not surprising that primates are often the focus of zoo-based research testing. Living Links is a purpose built research and science public engagement centre. The research is voluntary and non-invasive. The monkeys are never food or water deprived and research sessions take about ten minutes and happen a maximum of eight times a week. However, it is essential that we monitor the impact of such research on the welfare of the research participants.

Whilst some previous studies indicated that participating in research may be beneficial for primates, others indicated that it may be stressful and/or disruptive to their lives.

The observational study was carried out by Psychology student Suzanne Ruby under the supervision of Professor Hannah Buchanan-Smith from the University of Stirling. Suzanne observed the individual behaviours and social interactions of the Living Links capuchin monkeys following involvement in non-invasive voluntary behavioural research versus other occasions when the monkey was not involved in research.

Most of the findings were positive: following participation in research, general activity and stress related behaviours appeared to be relatively unaffected whilst the number of positive social interactions were enhanced. A goal of environmental enrichment is to enhance such affiliative interactions, as these are indicative of a positive welfare state.

However there was also an increase in aggressive interactions following involvement in research; none of these interactions resulted in injury, but it is important to consider how we can minimise negative interactions. The researchers believe this aggression may have been caused by food held by the participating monkey as they left the research cubicle. Thus researchers will now be advised to allow the capuchins time to consume the food rewards before giving them access to the group.

This study has highlighted the need to carefully monitor research techniques but has largely demonstrated that taking part in research may have beneficial effects on captive primates. We must ensure that we continue to develop our understanding of the impact our interventions have on captive primates, and continue to improve our techniques.

Ruby, S. & Buchanan‐Smith, H. M. (2015). The effects of individual cubicle research on the social interactions and individual behavior of brown capuchin monkeys (Sapajus apella). American Journal of Primatology. 

A recently published study has shown that monkeys with similar personalities are more likely to have better relationships than those with very different personality traits. Some of the key indicators that were connected with how strong their relationships were linked to their levels of openess and sociability.

In order to determine the monkeys’ individual personality differences the researchers used a 54 trait personality questionnaire that the zookeepers completed for each monkey. Then to determine the quality of their relationships they conducted behaviour observations.

The behaviour study included noting how much time the monkeys would spend together, as well as what they were doing when they were together (e.g. aggression, food sharing, grooming etc).

In addition puzzle feeders were added into the enclosure to see if the monkey pairs showed symmetry in their behaviour to use the device or avoid it.

While watching the monkeys Dr Morton noted high levels of affiliative behaviour between Popeye and Penelope (pictured above), as well as high levels of symmetry in their behaviours around the puzzle feeder. Interestingly, these two monkeys also had similar personality traits appearing in their scores from the keeper surveys.

The results remained true even when other factors such as sex, age and rank were controlled for. These findings mean that their personalities may play a role in the quality of their relationships beyond that of status and kinship.

Morton, F.B., Weiss, A. Buchanan-Smith, and Lee, P.C (2015). Capuchin monkeys with similar personalities have higher quality relationships independent of age, sex, kinship and rank. Animal Behaviour.105, pp. 163 -171.

Sharing is a prosocial behaviour, one that individuals do to benefit others. Living Links researchers and others from American institutes have recently published a paper looking at how these three species compare.

The main aims of the research were to;

1 – Compare the ability to be prosocial in chimpanzees, capuchins and humans of various ages by using the same method across all three species.

2 – Investigate if experiencing prosocial behaviour will then in turn influence individuals to be more prosocial.

The apparatus that was used in the study has been nick named the ‘Shelfish Apparatus’. The device has two sliding shelves with rewards on them of varying levels (i.e. some high food rewards and some low food rewards). One primate has the power to pull the shelf where the other will just receive what the other primate has chosen in the pull.

Note: Stickers were used in the human test scenarios instead of food items.

In the first part of the study where the species were compared against each other they tested various scenarios. In all cases the puller was always given 2 shelves with rewards of the same value, the receiver side had the varying levels of rewards.

Some of the scenarios they tested were;

Empty control – They could pull the shelf towards them to receive a reward with no one next to them.

Prosocial option – They could pull the shelves with a neighbour there to also receive a reward.

The results showed the most significant prosocial behaviours occurred in separated chimpanzees when they received a more preferred food reward.

Adult humans would still pull the shelf with a more preferred reward for their partner even if they received a less preferred reward themselves.

Finally like the chimpanzees, the older human children were only significantly prosocial when they received a more preferred reward.

As for our capuchins…well when they were tested in the prosocial condition they only gave the receiver a more preferred food reward by chance.

In the second part of the study our researchers wanted to find out if experiencing prosocial behaviour would then encourage and individual to then become more prosocial.

They tested this in a very clever way that took out the chances of the prosocial behaviour just being reciprocal. The experiments were run in three phases with chimps, children and capuchins.

In the first phase was done the same as the prosocial condition in the above tests. The second phase let them experience another primate that was always prosocial to them and then third they were retested with their original partner.

In this study chimpanzees were significantly more likely to be prosocial after they experienced someone being prosocial to them. This was also true for the children aged 7 and older. Both the capuchins and younger children were still only demonstrating prosocial behaviour by chance.

So what do these results mean in terms of the evolution of prosocial behaviours?

One of the authors on the paper, Professor Whiten states:

“We believe our study is the first to demonstrate that the prosocial behaviour of humans and non-human primates is shaped by the everyday social actions of those around them. Kindness may thrive, evolve and inspire when helping, sharing or donating are part of the cultural experience.”

To read the full article click on the reference link below.

Claidiere, N., Whiten, A., Mareno, M.C., Messer, E.J.E., Brosnan, S.F., Hopper, L.M. Lambeth, S.P., Schapiro, S.J. & McGuigan, N. (2015). Selective and contagious prosocial resource donation in capuchin monkeys, chimpanzees and humans. Scientific Reports, 5: 7631. DOI: 10.1038/srep07631

An animal’s personality can be defined as a consistent pattern of behaviour and thinking.

Twenty of our squirrel monkeys have been personality surveyed by our keepers. This entails the keepers giving our monkeys scores on certain characteristics in their behaviours. For example they look at traits such as sociability, curiousity and timidity (Fig 1).

These traits can then be categorised into broad personality factors. For humans we have five recognised personality factors, whereas the squirrel monkeys are seen to have four (Fig 2).

Some of our squirrel monkeys like Ellie and Georgette (Fig.3) have scored high in assertiveness, whereas others like Toomi and Salvador have scored higher in impulsiveness.

 

You are probably wondering ‘when does the poo come into this story?’ And the answer is now.

 

 

Vanessa Wilson from Edinburgh University has gained the personality profiles of our monkeys from the zoo keepers’ surveys. What she can now look to see is if these match up with specific genes in the monkeys’ DNA.  The way we get the DNA from the monkeys is by sampling their faeces.

To be sure we match up the right monkey to the correct faecal sample we need to add a marker to their food. Glitter is perfect for this, in fact silver and green glitter seem to work the best (Fig. 4).

What we are looking for in the DNA of our monkeys are variations in some very specific genes. The ones in question are named DRD4, 5HTT and MAOA.  These genes are directly linked with either dopamine or serotonin systems in the brain (Fig 5).

Dopamine and serotonin play a large role in animal behaviour and personality, so differences in these genes may allow us to see why some of our animals have different personality types.

Similar research has taken place with other animals too, including elephants, orangutans, and dogs. The more species we study, the greater understanding we will have on the connections between animal genes and behaviour. This knowledge can then help us to ensure genetic diversity in captive breeding programmes as well as tailoring or animal care procedures for specific personality types.

 

 

 

Researchers, including Dr Catherine Hobaiter from the University of St Andrews, have observed the spread of a new tool being invented and used by a group of wild chimpanzees. This is the first time that researchers have been able to track the spread of a natural behaviour from individual to individual in the wild.

Guest Blogger – Annabel Scott , BSc Environmental Stewardship –  Glasgow University

In a recent study by Wilson et al. (2013), the facial structure of capuchin monkeys was examined to see whether differences in this link to different personality traits.

Sixty-four capuchins were examined from three institutes: our Living Links monkeys here in Edinburgh Zoo, the Language Research Centre at Georgia University and the Laboratory of Comparative Ethology at the National Institute of Health.  Front facing photographs were used to find the measurements for each capuchin.  fWHR (facial width to height ratio) was determined by the ratio of bizygomatic width to upper face height as shown below.   Lower face/face height (eyelids-chin/height of whole face) and face width/lower face height (bizygomatic width/height of whole face) were also calculated.

 

 

 

Personality ratings were collected for each individual by a measure used in non-human primates.  These were scored on a 7-point scale, which ranged from no signs of the trait (1) to extreme display (7).  Five traits were looked at; assertiveness, openness, attentiveness, neuroticism and sociability.  Below are photos that illustrate the differences in capuchin face morphology.

 

 

Examinations of lower face/face showed a significant effect of age as the ratio increases, however no sign of sexual dimorphism.  Neuroticism was found to be non-dimorphic in capuchins, but in humans both neuroticism and lower face/face height are sexually dimorphic.  fWHR is not sexually dimorphic in humans.  Capuchins with higher ratios of lower face/face height (longer lower face) were found to be more neurotic and less attentive.  Therefore facial morphology of capuchins determines three personality traits: assertiveness, attentiveness and neuroticism.

 The following graph (Fig. 1.) shows how face width/lower face height has a significant age × sex interaction, with males showing a higher face width/lower face height ratio than females.  These sex differences increase across the life span.  Humans also exhibit sexual dimorphism in this facial metric, however women show higher ratios than men and this also increases with age.

fWHR and face width/lower face height both showed a link to assertiveness.  One possible reason that these facial metrics relate to personality is due to the connection with status and leadership traits.  Status in humans can be based on force or friendship, lower face/face height however, may be driven by vigilance and attention span, therefore linked to a social form of status.

Openness and sociability appear to affect sociality and cognition in capuchins.  Sexual dimorphism may be linked to differences in morphology, so future work with these species may help to understand what determines species-specific personality traits and why they are associated with facial structure.

Further studies could look at sex-specific age growth in capuchin facial metrics and could also examine the effects of location and body weight.  Examining the lower face/face height further could tell us the origins of status effects on well-being and emotional traits, which could be linked to status in humans.

Reference

Wilson, V., Lefevre, C.E., Morton, F.B., Brosnan, S.F., Paukner, A. and Bates, T.C. (2013). Personality and facial morphology: Links to assertiveness and neuroticism in capuchins (Sapajus [Cebus] apella), Personality and Individual Differences. (IN PRESS)

 

 

 

 

 

 

 

 

 

The ability to learn patterns, ultimately the rules of language has rarely been studied in new world primates. In this study the researchers use species specific sounds/tones to determine if the squirrel monkeys were able to decipher when the correct order and incorrect order of these sounds were played. This is the first study that has used species specific frequencies in order to test their abilities. Other studies relied on humans producing syllables, which may not have been the most appropriate way to measure the monkeys’ capabilities.

Two ordered sound patterns were tested with the same rule being applied of A Bⁿ A.

Test 1 – Low Tone= A, and High Tone = B (eg. Low, High, High, High, Low)

Test 2 – High Tone = A and Low Tone = B (eg. High, Low, Low, High)

The results suggest that the monkeys were able to consistently decipher when the rules were being broken in both the test settings.

These finding suggests that the ancestor of both squirrel monkeys and humans which existed approximately 36 million years ago would also have been able to understand the rules involved in pattern learning, thus most living apes and monkeys today should also be able to do this. This skill may have evolved as a cognitive ability rather than a direct pre-cursor to language.

Ravignani, A., Sonnweber, RS., Stobbe, N. and Fitch, TW (2013). Action at a distance: dependency sensitivity in a New World primate. Biology Letters. 9. 20130852

Ruth Sonnweber, one of the scientists from this study is now continuing similar work here with our squirrel monkeys in Living Links, however instead of sound stimuli she has been using touch screen to determine their ability to learn patterns.

 

 

Chimpanzee Alarm Call Production Meets Key Criteria for Intentionality

Determining the intentionality of primate communication is vital to understanding the evolution of human language. Although intentional signalling has been studied for some great ape gestures, comparable evidence is currently lacking for their vocal signals.

In this study the following criteria were used to analyse if the Sonso group of chimpanzees in the Budongo Forest in Uganda were communicating with intention.

 

 

 

 

 

 

The researchers presented the chimpanzees with a python model with up to 4 observers recording the calls and behaviours of each focal individual.

 

 

 

 

 

 

 

Figure – The snake image represents the location of the python
model, concealed by leaves. Observers and their main roles are defined. The
chimpanzee image depicts the focal chimpanzee, who could be accompanied by
other group members depending on the experimental condition.

The results of this study indicate that some chimpanzee calls meet the criteria for intentionality, for example most chimpanzees who had seen the snake model gave calls and demonstrated gaze alternation and audience checking with a fellow chimpanzee. ‘Waa Barks’ (WB) and ‘Alarm Huus’(AH) were produced in the presence of socially important individuals who had not seen the snake. Furthermore , WB’s and AH’s were increased in the presence of friends vs. non-friends.

The researchers believe that their findings disagree with the gestural theories of language origins and instead support a multimodal origin for human language.

Video illustrating gaze alternation and looking at a group member before producing waa barks. Video is filmed from position 2. Focal adult female Nambi reacts to the arrival of her adult son Musa by turning and looking at Musa before producing her first waa barks of the trial. Nambi then looks immediately back at the snake, showing gaze alternation between the recipient and the snake whilst calling. During Nambi’s waa bark production, Musa stands bipedally.

 

Schel, AM., Townsend,SW.,Machanda, Z.,Zuberbuhler, K., and Slocombe, KE. (2013). Chimpanzee Alarm Call Production Meets Key Criteria for Intentionality. PLoS ONE 8 (10): DOI: 10.1371/journal.pone.0076674