Comparison of observed transport speeds with those expected under three different models of interaction among porters.

Observed speeds are given as the average ± standard deviation of group speed (cm/s) for three different group sizes. The three columns to the right give the corresponding values estimated from 10,000 simulated data sets. Each simulated set includes the same number of groups as the observed data (given by n in the column of observed speeds). P-values give the proportion of simulated average speeds that were more extreme than the observed average speed for each group size.