The reason that between-group differences are greatest for LE is that repertoire optimization is lowest for LE (Fig. 3 c, compare blue to orange and red). In SE and especially OL, greater repertoire optimization  leads to convergence in repertoires between groups, diminishing between-group differences. For between-group differences, we find nearly the exact same pattern as for traditional differences (compare Fig. 3 a with Fig. 2 a). For within-group similarity over time, we find that similarity is high overall (Fig. 3 b), but lowest for LE (blue), and greatest for OL (red). Given that we calculate traditional differences based on (1) between-group differences (1 - between-group similarity) and (2) within-group similarity across time, between-group differences are the main determinant of traditional differences in our results. Thus, even though LE exhibits the lowest within-group similarity, due to large between group differences, LE exhibits the greatest traditional differences. Fig. 3Between-group differences (1 - between-group similarity) (a), within-group similarity over time (b), repertoire quality c for different task difficulty (H), and different kinds of cumulative process for OL at H=10 (d). For a–c: Blue = LE, Orange = SE, and Red = OL. LE and SE are inviable at H10 and are excluded. Each data point is the mean of 10 simulations, and whiskers show standard deviation. For d: Boxplots show minimum, 1st quartile, median, 3rd quartile, and maximum, where data comes from 10 simulations. The calculation of repertoire statistics and cumulative cultural change is explained in the ’Simulations and analysis’ section