1. Non-kin interactions: Reciprocal altruism in animals
Allison Block, Chelsea SoLOMita, & Lily Tucker
We want to keep this very succinct because we know a lot of groups have to present the same day as us!
Stevens, J.R. & Hauser, M.D. (2004). Why be nice? Psychological constraints on the evolution of cooperation. Trends in Cognitive Sciences, 8(2),

2. Key points
Reciprocal altruism is present in non-human animals, but more rare than in humans
This is likely due to psychological/cognitive restraints including:
Temporal discounting
Numerical discrimination
Memory
Reciprocal altruism is when the donor and the recipient alternate roles and have repeated altruistic interactions. It is key to human society but seems to play a more minor role in non-human animals.
Animals definitely do display some reciprocal altruism. The article presents a couple of studies of species like birds do show reciprocal altruism, though noting that it can be limited.
They propose that this is due to the fact that reciprocity may be too cognitively demanding for many animals. A few of the main cognitive restraints are temporal discounting, numerical discrimination, and memory skills.
Temporal discounting means that future rewards decrease in value, so a smaller but immediate reward is preferred over a larger reward later on. In the animal world many uncertainties about the future may lead to increased temporal discounting. Animals do not seem to possess the ability to employ delayed gratification as humans do. Reciprocity means an immediate cost for future benefits (to the original donor from the original recipient), so it makes sense that animals would have a hard time making this work for them.
Numerical discrimination has to do with quantifying numbers and quantities of things. Animals actually do have some number sense, but it is very minimal compared to humans. It seems that rats and pigeons can count precisely up to about four, but after that they approximate. Similarly, monkeys know that four bananas is better than two, but if the numbers go higher than that, they have a hard time deciding between quantities unless the difference is large. This suggests that animals can have successful reciprocal exchanges when the resource or item is of a quantity of four or less, but when the numbers are larger it is simply an approximation and it is no longer clear if the later benefits live up to the original aid from the donor.
Lastly, memory studies regarding animal cooperation have not been done extensively, but inferences can be made from human studies. Memories tend to decay over time, so the longer the interval between reciprocal exchanges, the more difficult it will be to maintain this reciprocity and keep track of the exchanges. Time is not the only issue – there is also the fact that other exchanges will occur, and keeping track of multiple reciprocal relationships may be too much of a memory load. Animals could easily mix up who owes them, who they owe, and so on. In time, animals probably just forget some debts altogether.
For all of these reasons, reciprocal altruism is more rare and less impactful in non-human animals.
Stevens, J.R. & Hauser, M.D. (2004). Why be nice? Psychological constraints on the evolution of cooperation. Trends in Cognitive Sciences, 8(2),

3. Critical review Particularly interesting points:
Rats and pigeons can count?!
Animals are like young human children in terms of delayed gratification
It was very interesting to see that rats and pigeons that were taught to press a button a certain number of times for food could press it precisely up to four times, and more amazingly that even in larger numbers they could approximate within +/-5 (such as stepping on the button 20 times when they were required to do 24). True, this is far less than humans are capable of which explains why it could inhibit reciprocity, but we thought this actually was good evidence for how reciprocal relationships can indeed work for animals in many situations.
The part about animals having a hard time with delayed gratification reminded us of studies we’d seen in lifespan development class that showed young children having a very difficult time with delayed gratification. As they grow older, they significantly improve, and clearly human adults understand delayed gratification and value larger rewards in the future. It is like animals are stuck in a juvenile stage of development compared to humans and it would be interesting to see if, with extended teaching, they could learn to understand delayed gratification and perhaps one day even evolve to understand it.
Stevens, J.R. & Hauser, M.D. (2004). Why be nice? Psychological constraints on the evolution of cooperation. Trends in Cognitive Sciences, 8(2),

4. Critical review Confusing points: Memory section was unconvincing
Different species have different intelligence
The section on learning and memory was a bit confusing. It mentioned an alternative to the tit-for-tat strategy called win-stay/lose-shift, which was hard to wrap our heads around. Furthermore, the evidence for memory decay over time and for interference by other events and exchanges is from human research. It is reasonable to assume that these findings could be applied to animals, but specific experiments on animals would be more convincing.
One thing we found ourselves thinking as we read this is that the article seems to be generalizing all animals. Much of the research involved rats, pigeons, or monkeys, and just within those species there is obviously a wide range of intelligence. What about lizards compared to dolphins, for example? Different species have very different cognitive abilities and restraints, so it seems that generalizing them all is restrictive. A more specific article focusing on just monkeys, or just rats, and so on may provide more insight.
Stevens, J.R. & Hauser, M.D. (2004). Why be nice? Psychological constraints on the evolution of cooperation. Trends in Cognitive Sciences, 8(2),

5. Video
Dawn of Social Networks: Hunter-gatherers Provide Clues About the Evolution of Cooperation
The video is a bit separate from our article.
The takeaway message of this video is that in human populations, both those in the EEA and in modern times, cooperators seem to stick together to help each other and avoid selfish cheaters.

6. Discussion
Although this study is about animals, it helps us understand what psychological and cognitive mechanisms are crucial for humans to engage in reciprocal relationships.
Can anyone think of an example of a time when they helped/cooperated with someone who wasn't in their family? What was your motivation? Was it really altruistic?
Stevens, J.R. & Hauser, M.D. (2004). Why be nice? Psychological constraints on the evolution of cooperation. Trends in Cognitive Sciences, 8(2),