Figure 2.

Experimental data. (a) Scatter plots of the final decisions of the last 30 trials in the x₁x₂-plane for the three Prisoner's Dilemma games, where subjects' actions are expected to cluster around the single pure Nash equilibrium located in the top-right corner at position (1,1). (b) Two-dimensional histograms of the experimental scatter plots. (c) Final decisions with binary categorization. (d) Both players’ response frequency λ calculated from the categorized actions of the last 30 trials. The experimental data are shown with stars, whereas the circles represent the quantal response equilibria fitted to the data according to equations (6) and (7) with β₁ = 2.14 and β₂ = 3.04. (e) Player 1's response frequency of defecting across game conditions. The central marks indicate the median and the edges of the box are the 25th and 75th percentiles considering all trials and subjects. (f) Box plots for player 2's response frequency across conditions. (Online version in colour.)