a, Four examples of exponential (red) and cubic (green) fits of the raw data (black plain line) for green scales; the mean square difference per point is generally lower for the cubic than the exponential fit. The graph labelled (I) is an example of a time point for which the value for 6 neighbours is not available, so this value is estimated with the fitted curve. b, On the left is a polynomial cubic fit of the 13 colour change probability distributions corresponding to three different individuals (blue, red and green curves) at different time points; the four curves labelled with Roman numbers correspond to the four graphs in a; all values are normalized with respect to the highest probability. In the middle is a normalized colour change probability distribution; each of the curves is normalized such that the sum of probabilities is 1. On the right the 13 normalized curves define a mean (±s.d.) colour change probability distribution.