The new experiment holds the payoff function constant and only changes cohort size and order statistic. A finer approximation makes it less costly to explore locally and, hence, may destabilize inefficient mutual best response outcomes. The PDF file size is 444k. Changing the order statistic is more powerful than changing group size. The order statistic also influences initial behavior, which exaggerates the stochastic dominance relations, see table 2.
Subjects focus on the observed order statistic and then explore locally.
This local exploration is skewed in the direction of efficiency. Reducing the opportunity cost of local exploration increases subjects' propensity to experiment with actions slightly higher than last period's order statistic. W.J. Conover, Practical Nonparametric Statistics , 2e.