Sunday, March 05, 2006

With A Little Help From My Friends

Two new papers in Science on the collaborative tendencies of chimpanzees and human infants shed light on the nature and evolution of cooperation and altruism.

Although the image of nature as ‘red in tooth and claw’ has an established pedigree, and great popular resonance, the role of cooperation in nature has also been long recognised (1). The extreme form of cooperative behaviour that social insects, such as bees and ants, engage in, in which some individuals sacrifice reproduction seemingly for the good of the hive, posed problems for Darwin. But modern theories of the evolution of cooperation, such as W. D. Hamilton’s kin selection theory, and Robert Trivers’s idea of reciprocal altruism, have helped explain otherwise puzzling cooperative behaviour in a range of species.

But we humans stand out as an evolutionary anomaly because of our propensity to behave cooperatively or altruistically in situations that cannot easily be explained by kin selection or reciprocal altruism. Our altruistic acts often extend well beyond the confines of our nearest and dearest. We (well, some people at least) donate blood, give to charity, do voluntary work, and go out of our way to avoid affecting others with our pollution.

In fact, modern experimental results of how people behave with regard to others are increasingly leading to the view that humans are motivated by a genuine concern for others, and not merely disguised selfish interest, genetic or otherwise. At the very least, gene-based models of the evolution of cooperation might need to be augmented with studies of cultural evolution and gene–culture co-evolution (2).

There are many components to the human capacity for altruism and successful cooperation. Empathy is an important motivating factor in driving people to altruistic acts of help in response to seeing people in distress. It is also useful to have a sense of fairness, which helps to avoid being exploited in ‘collaborative’ acts. Sarah Brosnan and Frans de Waal have shown that Capuchin monkeys refuse to participate in ‘work’ if they see another monkey getting a better reward for the same labour. This effect is amplified if another monkey is openly rewarded for no effort at all in front of a working monkey (3). At a more basic level, organisms often need to understand the sort of help required by other individuals in need in order to act effectively. And if individuals are to engage in successful cooperative acts, it is useful if they can identify those with whom they can work well.

Monkey see, monkey do
The first paper in Science (4), from Alicia Melis and colleagues, looks at the last two skills in chimpanzees. The findings strongly suggest that chimps can understand when help is needed, at least in the experimental set-up used in this study, and what the appropriate thing to do is to solve the problem at hand. They also show that when selecting a partner for a cooperative endeavour, chimps pick individuals on the basis of whether they have previously had successful collaborations with them or not.

Part of the reason for exploring these skills in chimps is that, being our closest primate relatives, they can shed light on what mental faculties are unique to humans, and which are perhaps derived from a common ancestor with chimps. Faculties that are shared between chimps and humans are plausible candidates for the building blocks of human altruism, even if human social behaviour is transformed by cultural additions and modifications.

Melis and colleagues used an ingenious set up to explore the nature of collaboration in chimpanzees (see figure to the left). Two sets of experiments were undertaken. The first set looked at whether chimps recruited help more often when they needed it, and therefore whether they understood what needed to be done to solve the problem they faced. To test this, the researchers set up two experimental conditions.

In the first condition, food rewards were placed on a platform outside the test room (see figure above). A piece of rope was threaded through two loops on the food-bearing platform, and the ends extended into the test cage so that they lay 55 cm apart. A chimp (the subject) was then released into the test room. To get the food, the chimp merely needed to grab both ends of the rope, which were close by, and pull (if the chimp only pulled one end of the rope it would unthread through the loops). While the chimp pondered the problem, a partner chimp, visible to the subject, remained locked in a room adjacent to the test room. The lock to the room was a simple device. In any case, chimps had previously been introduced to the ‘pulling task’ to get the food, and also learnt to unlock the door to let another chimp out. So they could do one act (unlocking the door) in order to do the other (get the food). The researchers watched, waited, and observed what the subject did (this was called the solo condition).

In the second condition (called the collaboration condition), the ropes were placed 3 metres apart, so that the only way the chimp could get any food at all was by recruiting help from the locked-up partner to simultaneously pull on the rope (the chimps had shown they knew how to do this in training trials).

If chimps recruit help only when they need to do, so as to maximise the reward they get by acting alone, then they should have unlocked the partner more often in the collaboration condition than in the solo condition. And this is just what was found.

So this first set of experiments shows that chimps know when they need to enlist help, and when they can go it alone and reap more rewards for themselves. The second of set experiments shows that chimps can also enhance their likelihood of forming successful collaborations on the basis of previous experience with other chimps.

In this set of experiments, in addition to a partner in the same room as before, there was also a chimp in the second adjacent room. These two potential partners for the rope-pulling problem differed markedly in their skill at solving the task. The subject partner had previously had a limited number of interactions with both chimps independently in obtaining food from the platform. So the subject chimp, if it had learnt that one chimp was a better choice as a partner for solving the problem than the other chimp, would be expected to pick the better partner more often. And again, this is what was found. Interestingly, the chimps’ behaviour provided evidence that they were tracking the relative success of partners and updating their decisions on the basis of previous outcomes. The chimps basically followed a ‘win-stay/lose-shift’ strategy: if they were successful with a partner, they would pick the same chimp for the next trial, and if it was unsuccessful switched to the other (this wasn’t an absolute rule they followed, and there were exceptions).

So chimps seem to know whether they need help, and to know who to turn to when they do. It also shows that chimpanzees can adapt a new skill, such as unlocking a door, and use that to aid future collaborations (in setting a partner free to collaborate in getting food).

Of children and chimps
The second paper in Science (5), from Felix Warneken and Michael Tomasello, tackles a different set of questions. While the first paper, described above, reveals that chimps know when, and with whom, to engage in collaboration to maximise benefits to themselves, what about helping when you have nothing to gain? Humans do this all the time, from holding doors open for people behind us to picking up a book for somebody who drops one. And it is this tendency that Warneken and Tomasello explored in their experiments.

Human infants and three young chimps were used as the subjects in this study (the small number of chimps limiting the strength of conclusions that we can draw from this work). The infants were pre-linguistic 18-month olds, and they were presented with 10 situations in which an adult (a male experimenter in this case, and therefore a stranger to the child) needed help in some task. In one situation, the experimenter, while hanging up washing, drops a clothes peg, and pretends to be obstructed by the clothes wire so that he cannot reach the peg on the floor. The child can see what is happening, and can walk over, pick up the peg, and hand it to the experimenter. In another situation, the experimenter, carrying a stack of magazines, approaches a closed cabinet, and tries, unsuccessfully, to put the magazines into the cabinet but instead just hits the door. In this case, the child can walk over to the cabinet and open the doors. The 10 situations were grouped in to four categories, according to the nature of the situation presented to the child: out-of-reach, physical obstacle, wrong result, and wrong means.

The children were also tested in control conditions. In the experimental situation, the experimenter made it clear through facial expressions, bodily reactions and sounds that there was a problem, and that help was needed. In control conditions, the experimenter remained neutral and did not suggest that there was a problem.

Children were significantly more likely to help in the experimental condition in 6 out of the 10 situations – picking up clothes pegs and handing them to the experimenter, or putting fallen DVD boxes on top of a pile that the experimenter missed. As these children couldn’t speak or fully comprehend language, it is unlikely that they have merely learnt to help through verbal instruction, although social norms may well augment a tendency to help others (or, perhaps in some circumstances, curtail it).

The same studies were carried out with the three young chimps. Although the chimps tended to help in the situations in which an object was merely out of reach, they weren’t so forthcoming in tasks that required actions other than merely grabbing and passing. There are number of possible reasons for this discrepancy. Perhaps the children were simply more willing to help, and this expressed itself as greater help across a wider range of situations. Alternatively, the chimps might simply have been stumped by the problems posed – even if they had recognised that help was required, they might not have understood what the goal of the experimenter was or how to aid him. Children have pretty advanced cognitive skills, particularly in the social domain, from a young age, and this might have given them the edge in being able to provide help.

Time to sum up. Chimpanzees recruit help when they need it, and from the best available partners, suggesting that corresponding skills in humans have a perhaps ancient evolutionary origin. But chimps are not so good at providing help across situations that require different forms of help. Maybe this is because of cognitive limitations, or maybe because of altruistic limitations. Pre-linguistic children, however, are capable of recognising when someone else needs help in reaching some goal, and are willing and able to provide this help in a wide range of situations. This is a good foundation for producing adults that are also likely to provide altruistic help to others, including strangers. And this propensity can be enhanced through internalisation of social and cultural norms that promote prosocial behaviour.

But is this sort of behaviour completely non-selfish altruism? At first it would seem so, as the helper derives no immediate benefit. But that doesn’t mean there are no benefits, even if they are not immediately obvious. A reputation for being a good collaborator and an general altruist can do wonders for your social currency, and can enable you to participate in projects that might otherwise have been closed to you. In any case, a tendency to want to help is a crucial ingredient of human prosociality. The challenge still remains of fully fleshing out a theory of human altruistic behaviour.

1. See the contrasting views of ‘Darwin’s Bulldog’, T. H. Huxley, and the anarchist Prince Peter Kropotkin.

2. Fehr, E. & Fischbacher, U. The nature of human altruism. Nature 425, 785-791 (2003).

3. Brosnan, S. B. & de Waal, F. B. M. Monkeys reject unequal pay. Nature 425, 297-299 (2003).

4. Melis, A. P, Hare, B. & Tomasello, M. Chimpanzees recruit the best collaborators. Science 311, 1297-1300 (2006).

5. Warneken, F. & Tomasello, M. Altruistic helping in human infants and young chimpanzees. Science 311, 1301-1303 (2006).


Blogger DavidB said...

Interesting research. Of course, young children would interact mainly with close kin (parents and siblings), so 'altruism' in this case might be explained by kin selection. (Though I suspect that a strategy of 'be nice to these big powerful people' would be in the infant's own interest anyway.)

10:45 am GMT  
Blogger Dan Jones said...

I agree David, that the help offered by infants might not be driven by disinterested altruism that can’t be explained by kin selection, but by the ‘misfiring’ of kin-selected altruism. In fact this seems to be a common criticism interpretations of experiments on human altruism – that the experimental situations do not reflect real-world, historically encountered situations, and may therefore produce maladaptive behaviour (from the perspective of self-interest). I think there is room for reasonable people to disagree about what the current data tells us.

2:43 pm GMT  
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