Proceedings of the Annual Meeting of the Cognitive Science Society

In two behavioral experiments, we demonstrated that human observers can extract average body size from a group ofindividuals. In Experiment 1, we asked 38 participants to estimate the average body size from a group of 5, 10 or 15bodies that were presented in various angles of view (Profile, Three-Quarter, Frontal, and Mixed). Participants were ableto extract the average body size, but they systematically overestimated thinner body groups, and underestimated largerbody groups. Biases were generally reduced for smaller sets sizes and when bodies were shown in profile view, but thetrend was reversed for sets with larger bodies. In Experiment 2, we tested 37 participants and showed that the accuracyof their estimates was modulated by presentation time: Accuracy was poorest when groups were presented for 1s, butsignificantly improved for 3s and 5s presentations. Implications of these finding are discussed.