I hated group projects in middle school. Perhaps this was a clear sign of my introverted personality, but to my thirteen-year-old mind, it was easier for freeloaders to get away with a decent grade without doing their fair share of the work. Being the slightly obsessive student that I was, I would end up doing extra work. But when we had to have groups, I always preferred small groups of 3-4 people to larger groups. I figured it would be harder for the freeloaders to screw around without being noticed by the teacher. Perhaps I was thinking about it all wrong, though.

In humans, it is generally known that larger groups can positively impact performance on many tasks, because groups can synergistically posses emergent properties that individuals themselves do not possess. What is it about putting a bunch of animals (human or otherwise) together in one room that allows for increased competence? One possibility is that the responsibility for anti-predator vigiliance can be split among individuals over time, allowing others within the group to focus on other sorts of tasks. If you can be certain that I'm watching out for enemies, then you can spend your time solving other problems. Another possibility (that is not exclusive to the first possibility) is known as the pool of competence hypothesis: "individuals intrinsically differ in their probability of success, and, as a consequence, larger groups are more likely to contain individuals with specific skills, individual tendencies, or past experience," making it more likely that a given group will be able to solve a given problem.

Some studies in humans have suggested that there is merit to the pool of competence hypothesis, but a new study published this month in the journal Proceedings of the National Academy of Sciences tests the hypothesis for the first time with wild non-human animals: flocks of birds.

It is possible that increasing group size only increases efficiency up to a certain point, after which it levels off. In non-human animal groups, for example, food intake increases with group size at first, because the risk in hunting or foraging gets distributed among more individuals, allowing for more food to be consumed, overall. But once group size reaches a certain point, food intake decreases because of competition between individuals. And as group size increases, the possibility for freeloaders increases - just as in my middle school class - which also results in decreased food intake.

Zoologists Julie Morand-Ferron and John L. Quinn from Oxford University combined all these possibilities in order to generate two predictions. One possibility is that there exists an optimal group size where the net benefits of grouping are maximized if the increase in efficiency comes from reduced risk to the individuals. The other possibility is that there is a linear increase in problem-solving efficiency as group size increases and no optimal group size. This would support the pool of competence hypothesis, because larger groups ought to contain more individuals that are more likely to solve a given problem, compared with smaller groups. In the first case, the increase in efficiency is solely due to the presence of more individuals in a group. In the second case, the increase in efficiency is due to the increased diversity that comes along with larger groups.

To address their question, Morand-Ferron and Quinn set up five contraptions in five locations in the Wytham Woods area of Oxfordshire, UK, for five to seven days at a time, to study wild flocks of great tits (Paris major) and blue tits (Cyanistes caeruleus). All individuals of both species that are born or bred in Wytham have small transponder tags in them, which can be used by scanners to identify particular individuals. The contraptions consisted of containers of sunflower seeds with two levers attached. Pulling the levers sequentially, no matter the order, allowed thirty sunflower seeds to drop into a receptacle where they could be eaten.

They found that larger groups were indeed more efficient problem-solvers than small groups. But what was the mechanism behind this finding? They found that if there was just one individual in a group that had previously solved the problem (remember, the contraptions were in place for 5-7 days), increased problem-solving efficiency for the group, but this effect held even when controlling for group size - so this doesn't really tell us anything the pool of competence hypothesis.

The next thing that the researchers did was to only look at problem-solving attempts by naive birds - that is, individuals who had not previously solved the problem. And in this case, as with the entire sample, efficiency indeed increased with group size, and moreover, it did so in a linear fashion, instead of leveling off at some optimal group size. This was expected if the pool of competence hypothesis was correct: increased efficiency was due to the presence of more individuals who had the potential to solve the problem, rather than simply due to the presence of individuals with prior experience. They also found that each individual of the larger groups was able to eat more seeds than the individuals in smaller groups, whether or not that particular individual had been able to solve the problem him- or herself!

Notably, the increase in problem-solving efficiency doesn't just come from having more individuals in a group, it's about having a stronger diversity of individuals. The researchers write, "The advantages of diversity in group decision making have just begun to be investigated, with recent theoretical and empirical studies suggesting that collective diversity can sometimes trump individual ability...It is likely that a higher diversity of cognitive abilities, coping styles, or motor tendencies may have helped groups of tits at solving the novel problem over and above effects from reduced predation risk."

It might be, then, that one adaptive benefit of sociality, in both human and non-human animals, is greater efficiency in solving new problems, due to increased diversity. Which is something to consider, especially for the workplace and for the laboratory.

Great tit photo: Flickr/barnoid

Morand-Ferron J, & Quinn JL (2011). Larger groups of passerines are more efficient problem solvers in the wild. Proceedings of the National Academy of Sciences of the United States of America, 108 (38), 15898-903 PMID: 21930936