Do groups have a larger cognitive capacity than individuals?

Cognitive overload occurs when a decision-maker attempts to process more information than it can handle. This leads to the paradoxical result that enlarging the option set degrades decision performance. Past research on cognitive overload has focused only on individuals, but the concept may also be relevant to the collective decisions of animal groups. A group, however, can distribute the burden of decision-making among its members. Therefore, we hypothesized that a group has a larger cognitive capacity than any single member, and so is less vulnerable to cognitive overload. To test this, we compared the ability of Temnothorax ant colonies and individuals to choose the best among several nest sites. We found that individuals performed significantly worse when the number of options was 8 compared to 2. Colonies, on the other hand, performed equally well with either 8 or 2 options. These results suggest that a colony can evade cognitive overload by having each colony member assess only a subset of available options. We are currently examining this possibility using uniquely marked ants. Our findings suggest a previously unknown advantage of collective cognition.