You scratch my back, I'll scratch yours

Why do individuals make sacrifices for others that they're not related to? Chris Smith went for a wander along the banks of the River Cam with Anglia Ruskin University’s Claudia Wascher to hear about “reciprocal altruism”...

Claudia - Reciprocal altruism means that one individual show behaviour which is costly for the individual showing the behaviour however, this behaviour benefits another individual. One example would be alarm calling: if one individual gives an alarm call this is actually costly for the individual because it might attract the predator to itself but it might benefit individuals in the surrounding. Usually those individuals are not related so we cannot say that it’s benefitting related individuals but it’s unrelated individuals.

Chris - It’s like if I saw someone creeping up on you and they’re going to push you in the river over there and I shouted out Claudia be careful there’s someone going to chuck you in the river, they could come and push me in the river, so I’m doing you a service but I’m also taking a risk myself? So why is it reciprocal then?

Claudia - Because it is repeated in directions. Usually it is individuals showing this behaviour to warn other individuals who will help back in the future.

Chris - So I’m helping you with the expectation that when the tables are turned and you see someone about to push me in the river, you’re then hopefully going to warn me?

Claudia - Yes, exactly.

Chris - What other tangible examples are there of this happening then in nature?

Claudi - In primates, for example, your would see individuals grooming each other reciprocally so this can be measured up to the minute sometimes. One individual will groom another one for five minutes and would get exactly the five minutes back.

There is the alarm calling examples, so individuals warn other individuals. This is especially the case in territorial bird species for example. Here territory neighbours would get familiar to each other so they know each other and they would be reciprocal in attacking predators who enter the territories. Another example is food sharing. The vampire bats share food with other individuals in a reciprocal manner.

Chris - What do they share a jugular vein or something?

Claudia - Kind of. They are quite dependent on finding blood every day because otherwise they would starve to death. After they have been foraging they would then meet in caves and then sometimes there are individuals who haven't found prey during the day and other individuals would give them blood.

Chris - That’s jolly generous of them. What’s to stop someone cheating the system though because I could rely on you warning me I’m about to go in that river, but I might not return the favour? So how has it evolved do you think that actually we do scratch each other’s backs?

Claudia - As reciprocal altruism is depending on repeated indirections individuals would just stop at some point. If I see that I am giving you things like I’m grooming you or that I’m giving you food and I don’t get anything back from you, I will just stop the interaction. This is a situation where we have inequity aversion which is behaviour that individuals would respond negatively to a situation where they’re treated unequal.

For example, primates have been trained to exchange a piece of food with a human experimenter for another piece of food. In this experimental situation two primates have been tested with the human and one of the primates would get a grape for exchanging, and the other would get a cucumber and they like the grapes much more than the cucumber. So, at some point, the monkeys receiving the cucumbers actually stopped the interaction, stopped their behaviour, they stopped exchanging because they didn't like to be treated unfair. It went to a point that this monkey being treated unfair would even throw the cucumber at the human experimenter etc to really show that they really didn't like this behaviour.

Chris - That’s quite high level cognition though, isn’t it, for me to be able to tell whether you’re giving me a bad deal or not, I have to put myself in your shoes and ask what would you do to me and visa versa? So does that limit what sorts of species are capable of this sort of behaviour?

Claudia - Yes, definitely. Reciprocal altruism has been suggested as the form of cooperation which takes the most advanced cognition. There are certain cognitive prerequisites individuals need to have to engage in reciprocal altruism. One of these is inequity aversion, they need to be able to estimate what are the costs for me; what am I getting out of the interaction?

The second thing they need to know is they need to recognise individuals. They need to recognise their cooperation partners and to memorise them, which sound trivial, but it’s not as trivial for non-human animals.

The third thing is that individuals also need to be able to cope with the delay of gratification, because if I’m doing something which is costly for me now and I only get back the benefits somewhere in the future, I need to be able to cope with this delay. Which, again, sounds very trivial but we also know, even from humans that there is this is very very difficult for humans. When somebody tells you you can have this piece of cake now or you wait and you will get two pieces somewhere in the future, you’ll probably say I won’t wait I’ll just take this piece now.

Chris - But some people do have their cake and eat it straight away don’t they? Why do you thin this evolved in the first place?

Claudia - My guess would be that complex societies make it necessary. If you live in a complex society of unrelated individuals you probably need to cooperate with each other in order to achieve a common aim. It’s likely that if you repeatedly interacting with non-related individuals, a system like this evolves.