According to latest research by Claudia Rutte and Michael Taborsky , of the Univ of Berne, Switzerland, rats are capable of generalized reciprocity. The excellent paper is published in the freely available journal PLOS biology, so go have a look.
As per what is know about the evolution of Altruism, it is surmised that co-operation in groups emerges based on four types of reciprocity- direct, indirect, strong and generalized.
In direct reciprocity, one helps another person/animal because the other animal has helped oneself in the past. This requires cognitive capacities to recognize different individuals and require social memory as to which member of the group had helped and which had defected or free loafed. While some animals like the Elephant have good social memories and the ability to remember and recognize different individuals, most animals fall short on these traits.
In indirect reciprocity, one helps another because one has observed the other guy to have helped someone else. This again requires cognitive capacities to recognize and also to remember This is more so based ona reputation system, wherein you start trusting someone more if you observe him doing good deeds. In return you are likely to help the do-gooder , when he is in time of need.
In strong reciprocity, people punish the defectors or free-loafers or non-cooperators. This requires sophisticated cognitive abilities to recognize the defectors and a willingness to undergo cost to oneself while punishing the defector. this too, along with the above two, has rarely been observed in animals apart from humans.
Finally, generalized reciprocity happens when one indulges in good deeds towards a stranger juts based on the fact that one has in the near future received such help from other strangers. con specifics. There are variations on this theme, whereby if people have been put in a good mood (which is a substitute for having received a good deed) they are more likely to indulge in altruistic acts like picking up books dropped by a confederate. This type pf reciprocity does not make very strong cognitive demands as one just has to remember the summary of whether the environment is cooperative or not, to produce the right kind of behavior.
The authors, using some clever experiments demonstrate that rats are capable of generalized reciprocity.
In a nutshell (I'm simplifying a lot here, for details go read the paper), they put two rats in a cage, separated by a transparent partition, such that if one of the rats pulls a string, food would be delivered to the other rat. They ensure that rats learn how to pull the strings and are able to see that their action leads to food for the other rat.
In the experiment, they pair rats such that one rat, who can receive the food but cannot pull the string, is paired with a number of rats who have learned to pull the string. As a aresulkt the rat gets to get a lot of food over consecutive days because of the fact that her partner rat had pulled the string. Thse partner rats ar eall different. In the experimental test condition, the roles are reversed and the focal mice, who had received food due to some stranger rats pulling the strings, is now given an opportunity to pull the string and help a never-before-encountered rat. The result: the mice does pull the string a lot of the times to help the new partner.
In the other experimental condition, the same rat is put in the cage, wherein he can get the food if the second rat pulls the sting. this time too all the rats are new: but sadly for the focal rat, these stranger rats were never trained to pull a string. The result: they never pull the string, so the rat does not receive any food. This is also repeated for a number of days and then the roles are reversed. Now, a new stranger rat is placed in the cage with the focal rat, such that if the focal rat pulls the string, the new stranger rat would get the food. Alas, the lack of pulling of strings by the previous stranger rats makes the focal rat apathetic and she pulls the string less frequently and less enthusiastically. The difference is as huge as 20 % greater pulling when one had received help, compared to when one had not received help.
This seals the argument as per authors, that the rats are indeed capable of generalized reciprocity. They interaction between rats as as between strangers and hence the only reason that explains the difference in string pulling, in received-help versus not-received help is the fact that in former they were in a o-operative environment, while in the latter they were not. thus, their actions were based on generalized help they received from conspecifics and not based on any memories of who helped whom. this to me appears to be breakthrough paper and would lead to a reassessment of how altruism evolved.
The authors also discuss a lot of other possible explanations , and I come satisfied that the generalized reciprocity is the best one.
The author summary is provided below:
The evolution of cooperation is based on four general mechanisms: mutualism, where an action benefits all partners directly; kin selection, where related individuals are supported; “green beard” altruism that is based on a genetic correlation between altruism genes and respective markers; and reciprocal altruism, where helpful acts are contingent upon the likelihood of getting help in return. The latter mechanism is intriguing because it is prone to exploitation. In theory, reciprocal altruism may evolve by direct, indirect, “strong,” and generalized reciprocity. Apart from direct reciprocity, where individuals base their behavior towards a partner on that partner's previous behavior towards themselves, and which works under only highly restrictive conditions, no other mechanism for reciprocity has been demonstrated among conspecifics in nonhuman animals. Here, we tested the propensity of wild-type Norway rats to help unknown conspecifics in response to help received from other unknown partners in an instrumental cooperative task. Anonymous receipt of help increased their propensity to help by more than 20%, revealing that nonhuman animals may indeed show generalized reciprocity. This mechanism causes altruistic behavior by previous social experience irrespective of partner identity. Generalized reciprocity is hence much simpler and therefore more likely to be important in nature than other reciprocity mechanisms.
The NYT also has an article on this and you may like to check that too.