Density Model predictions vs. IBM predictions.

(a) Histogram: statistics of presence around the center of mass of the group for N = 100, predicted from 300 IBM realisations; red line: numerical solution of Eqs 5 and 6 (Δt = 10−2 s). (b) Histogram: statistics of presence around the center of mass of the group for N = 4, predicted from 106 IBM realisations; red line: numerical solution of Eqs 5 and 6 (Δt = 10−2 s); black line: statistics of presence around the center of mass for groups of 4 positions sampled from the red curve, and applying the same procedure than the one used to obtain the histogram from IBM realisations (106 samples). (c) Predicted propagation speed depending on group size. Open dots: IBM predictions (error bars lie within the point size). Black dots: Density Model predictions.