10 Feb 2021

The Social Rat – Social Learning

So, what is social learning? The Encyclopedia of the Sciences of Learning offers the following definition:
The term social learning usually refers to learning that is influenced by observation of, or interaction with, another animal or its products.
I think this definition is excellent. Note –

  • “observation of”, not mimicking or copying,
  • “or interaction with”, which is very broad in terms of behaviour, and
  • “its products”, that is the animal’s pheromones, odours, excreta, urine, milk, breath and so on.

There is a great deal that is still unknown about social learning, but it’s an area that several researchers are dedicated to. However, most of the research tends to focus on exploring avenues that teach us something about humans. There are also people studying animals in the wild for the sake of learning about the behaviour of these animals, and that's useful to us too.

So, firstly, a little bit of background and history. It was thought (for most of the last 200 years) that animals learned by either instinct or imitation. And, by imitation, I mean watching an individual do something and copying the behaviour. This is now thought not to be a primary factor in social learning for animals.

Rather than copying the behaviour, the learner animal is generally observing and getting information from the experienced animal, and this information can be used by the learner to make trial and error more efficient.

One notable feature of animals who live in social groups is the emergence of common behaviours that aren’t necessarily found in the same species living in a different geographical area. For instance, wild rats living in some coastal regions will dive for shellfish, while many of their inland cousins will not dive – even when offered a specific opportunity and a tempting reward.

The question of how animals learn these common behaviours has troubled ethologists for more than a century (or three!). At first, they plumped for copying, which has since been rejected – but if it’s not mimicry, what is it? Today’s article will look at how behaviour is acquired and how social animals learn these group specific behaviours. But first let’s explore instinctive behaviour.

What is Instinctive Behaviour?
Instinct refers to the Darwinian evolutionary aspect of behaviour, which is called adaptive behaviour. When a species demonstrate a behaviour that is beneficial (or essential) to survival, that behaviour becomes generalised in the species and hardwired genetically so that it doesn’t have to be learned by each individual in less efficient ways.

One such behaviour in rats is self-grooming. A baby rat begins to groom their face even before their eyes are open. They don’t have to learn the behaviour because the desire to do it is part of their genetic makeup. Yes, their first attempts may lack finesse, but this is because their motor function needs to practice and become skilled. Interestingly the whole process of self-grooming is generalised across several species of rodent (including rats and mice). All rats follow the same stereotypical pattern of grooming.

Over time, more pieces of the puzzle of how instinctive behaviour emerges come to light. There is likely some influence of epigenetics - the modification of gene expression (think- switching on or off specific genes) based on the experiences and environment of previous generations. And a concept that’s been raised but doesn’t seem to have much research into it yet, is the involvement of some kind of generational learning – that a behaviour is habituated in offspring by practice over several preceding generations.

Social Learning
When we talk about social learning, we are moving beyond instinct and talking about learning that influences the behaviour of the rat – often specific behaviours - and the learning must have a social context. There is a large body of research on social learning in rats, a significant proportion of which has been done by researchers like Laland and Galaf. Laland and his team did a quantity of work on social learning around food preferences in rats. It was based on differences of behaviour and diet observed in the wild, and it was uncertain as to why these differences were occurring, but the observational evidence was stacking up.

So, when we observe colonies of rats in the wild, in different geographical areas, we find that they have different habitats and varied food preferences based on the available food. Those preferences often give rise to very distinct feeding behaviours.

There are groups of rats whose main source of food is shellfish, which they dive to collect, and hunting groups; rats who hunt ducks, believe it or not! Some groups raid bird nests and live primarily on eggs and young chicks, while others catch baby fish from rivers. We are probably all familiar with the habits of city-dwelling rats, who raid bins and scavenge from human waste.

These all require unique skills and behaviours, which are not universal to rats. To find out how this happens the researchers moved the question into the laboratory, and it transfers quite well. Some of these studies have been repeated many times with different groups of rats.

For one study they used wild rats in outdoor enclosures. So, they were making the laboratory as close to wild living as possible. But in some ways it was very different from the wild as they were manipulating the colony, so, introducing new rats and things like that.

The information that they gleaned over time was mostly related to food choices, as that was primarily what they're looking at. They did it by a series of experiments that involved having two bowls of (different) food available all the time.

One of those foods - and it was a different one at different times, with different rats – was associated with feeling unwell through a previous manipulation. So, before they began the experiment, adult rats were given either food A or food B laced with something that would make them feel unwell. Alternatively, the rat had been given something else at the time of eating the food that made the rat connect that food with feeling ill. Then there were many different experiments, all using this setup.

So, what has been learned over this series of experiments? Several outcomes including:

  • When an adult rat associated feeling ill with a certain food they never ate that food again.
  • If that adult then had babies, they would be born with an aversion to the food.
  • The babies wouldn’t eat the food, but they also wouldn’t even go near the bowl.
  • This was true even when the mother rat was removed from the enclosure before the babies fed so, it wasn’t dependent on where the mother fed.

When a mother rat is lactating it is understood that the babies are getting olfactory cues - scent cues from the milk as to the foods that she has a preference for. So, that could be one influence that's pulling them towards the food that she will eat. But the researchers think that there is something more that is stopping them from even visiting the second food dish. And it's unclear as to what that is.

Other outcomes from the experiment include:

  • Babies will learn food preferences from the presence of an adult rat, who doesn't have to be the parental rat.
  • This can be the presence of the adult rat at the food dish - which will lead them to show a preference for the food that’s in that dish.
  • They will also learn from olfactory cues left by an adult rat. That is, they show a preference for a certain food (dish) where an adult rat has previously fed.

Of course, there is some trial and error involved in food preferences, but that's not social learning. The trial and error for food preference learning is based on 'does it make me feel unwell?' So, a rat will always become reluctant to eat food that has previously made them feel unwell. This is why certain antibiotics are quite difficult to give to rats because they cause nausea, after which, it becomes nearly impossible to get the rat to ingest them.

Now, there is some evidence from other studies that rats will learn from the smell of foods on the breath of another rat. But that is only in terms of positive preference. There is no truth - and it has been tested in the lab - that a rat will learn not to eat a particular food by these means. So, a rat can come across another rat who is unconscious from eating a certain food, and the smell of the food is on the rat, the naive rat still won’t learn not to eat that food.

As already stated, when we talk about social learning, we mean a situation where information is gleaned by a naïve rat from an experienced rat. This information is stored by the learner rat and used to their advantage. Mimicry was considered to be the main kind of social learning in animals - that they were copying the behaviour of the adults around them.

So, a body of research was dedicated to testing that theory, with the conclusion that it simply wasn’t true! True mimicry is actually quite an unusual way for animals to learn from each other. But often animals can get information from watching other animals, and that can make their trial and error process much quicker. Many varied studies show rats are more likely to do something if they are with a rat who already knows how to do that thing.

A nicely executed study trained a group of rats to forage for buried carrots, two pairs of these trained rats (trainers) were put with two pairs of naïve rats (learners) making two groups of four. There were two more groups, each made up of four naive rats.

Then the four groups of four rats were put into different conditions.
1. One group of four naïve rats had a habitat where carrots were buried, but there was no trainer rat.
2. One group of four naïve rats had a habitat where no carrots were buried, and there was no trainer rat.
3. One group of teacher/learner pairs had a habitat where no carrots were buried.
4. One group of teacher/learner pairs had a habitat where carrots were buried.

The only group where the learner rats learned to dig carrots was group 4. Since digging is an instinctive behaviour, it wasn’t a lack of ability to dig that stopped the other naïve rats from digging for carrots. What they lacked was an experienced teacher rat to show them where the carrots were buried (always in the same place).

I would suggest that left in the habitat for long enough the naïve rats would find the carrots through trial and error in the conditions where carrots were buried. But gaining information from a teacher rat made the route to success much quicker.

Another experiment involved looking at the time it would take a rat to get the food located at the end of four arms of an eight-armed maze. So the arms were in the shape of a ‘star’, all coming out from the centre where there was a wire viewing box. The arms were essentially short square-edged open-topped tunnels with coated wooden walkways.

So, the researchers placed sugar pellets at the end of the arms that pointed North, South East and West, and nothing in the arms that lay between each of these points. The first rat was placed in the centre and timed completing the task of finding all of the sugar cubes. A second rat was placed in the viewing box, who could see the first rat at all times.

The first rat completed the task by investigating – entering each arm of the maze to find out whether or not there were sugar pellets at the end. The observer rat then had the opportunity to complete the task after the first rat was removed and the walkways cleaned. The whole experiment was repeated with several rats.

All of the observer rats were quicker and more efficient at completing the task, often passing over the arms where there was no food. Through observation, they had gained important information that enabled them to make better choices when completing the task.

Now when I say observation – I don’t just mean watching. A rat would be getting all sorts of clues, such as how long the rat stayed in an arm, and whether they were eating in an arm where sound and smell would inform as much as sight. This study is another example of a rat taking information from another rat and learning, without copying the behaviour of the ‘teacher’ rat.

One type of learned behaviour that was always assumed to be mimicry was between a mother and her babies. It’s thought now that this is likely to be driven by the desire of a mammalian baby to be physically close to the mother. So, a kitten who climbs up a tree after a mother cat hasn’t looked at the mother climbing and copied her behaviour. Rather, he follows her everywhere, both horizontally and vertically! The ability of a cat to climb is likely to be instinctive.

The final series of studies that I want to look at for this article, is one about swimming and diving in rats, which I find very interesting. There were several related experiments that would take too long to explain in detail, so let’s just take a look at some of the results they recorded. Firstly they discovered that swimming is probably an instinctive behaviour in rats and one that is honed as a wild juvenile simply by following their mother into the water. Diving is thought to be an exploratory take on swimming (much as climbing is to walking and running). Rats who can’t swim don’t dive.

There’s another interesting twist in as much as domestication seems to have damped down the instinctive swimming behaviour. When caged wild rats were given a habitat with swimming opportunities and observed for a week, almost all of them swam. The same setup was offered to a group of lab rats and only 50% took to the water.

Most rats can be taught to swim by starting with them paddling through very shallow water to get to their food and gradually increasing the depth until the rats will swim to get food. Once a rat is swimming regularly they will usually start to dive as an exploratory extension – or for a reward. The experiments used chocolates at the bottom of the diving pool.

However, rats will choose a less appetising food on dry land in preference to diving for a high-value reward. They only dived when no other food was available – when the researchers limited food to 3 hours a day. But when food was freely available all of the time, all of the chocolates remained in the pool! The same has been observed in wild colonies who live close to the water – they dive for food when other food sources aren’t available.

To bring things to a close, we’ll end by acknowledging that there are many questions about social learning, and currently a few tentative answers. What is clear is that a rat can glean important information from another rat, that can help it to complete a task or practice a behaviour. However, there is much of their communication that we know little about, such as vocalisation, pheromones, other odorants, body language – all of which are informing a naïve rat. There is still much to learn.

References
Nature Reviews Neuroscience 2016 Jan; 17(1): 45–59.
Neurobiology of rodent self-grooming and its value for translational neuroscience
Allan V. Kalueff, Adam Michael Stewart, Cai Song, Kent C. Berridge, Ann M. Graybiel, and John C. 
Fentress

Social Learning in Animals:
Empirical Studies and
Theoretical Models
Bennett G. Galef Jr. and Kevin N. Laland

Animal Learning & Behavior volume 18, pages246–251(1990)
Social learning and social transmission of foraging information in Norway rats (Rattus norvegicus)
K. N. Laland & H. C. Plotkin

The Royal Society Open Science 20 September 2017
Learning of efficient behaviour in spatial exploration through observation of behaviour of conspecific in laboratory rats
Yuji Takano, Masatoshi Ukezono, Satoshi F. Nakashima, Nobuaki Takahashi and Naoyuki Hironaka

Developmental Psychobiology 15(4):279-95 July 1982
Studies of social learning in Norway rats: A brief review
Bennett G. Galef