We are adapting ideas from psychology to understand how an ant colony functions as a single cognitive entity. We are particularly interested in differences between the performance of the whole colony and the individuals composing it. Much of our work centers on nest-site selection by Temnothorax ants. We have discovered that individual ants are prone to irrational changes in site preference when presented with certain challenging decision problems. Similar irrationality is well known in many animals, including humans. However, when colonies received the same challenge, they showed rationally consistent preferences. This suggests that groups can improve the quality of their decision-making by sharing their cognitive burden across many individuals.