Figure ESM4 from Social learning and the demise of costly cooperation in humans

Regression to the mean in public-goods games. Shown are the individual changes in cooperative contribution relative to their prior contribution, for individuals receiving no-information between periods, plotted against the individual’s prior deviation from the mean cooperation of their groupmates (filled grey circles, 1,440 observations). Dashed and dotted lines show the maximum possible increase and decrease respectively for each possible value of deviation. The bounded nature of the data constrains changes depending on deviation. The solid line shows the significant negative regression to the mean (controlling for individual, N = 288). Relatively low cooperators are significantly likely to increase their cooperation and vice versa even when they have no information about the behaviour of other players. This statistical artifact can give a false impression of players conforming to average group behaviour.