Fig. 2
From: Evolution of indirect reciprocity under emotion expression
Contourplots of cooperation by error magnitude, for each of the studied errors \(\varepsilon , \alpha , \chi\), respectively. Encoded by colour, according to the colour bar on the right-hand side, we plot the cooperation index difference between emotion-based image scoring and basic image scoring, by \(\gamma\) value on the y-axis and by error magnitude on the x-axis, from among the following values: \(\varepsilon , \chi , \alpha \in \{\frac{10^{-3}}{z}, \frac{10^{-2}}{z}, \frac{10^{-1}}{z}, \frac{1}{z}, \frac{10}{z}\}\), where z is the population size. For high \(\gamma\) values, we can see that the greater the magnitude of each error, the greater the impact of using an emotion-based social norm, with two notable exceptions: when errors become too frequent (\(\varepsilon =\chi = \alpha = \frac{10}{z} = 0.2\)—one error occurring on average in every 5 interactions), and when \(\gamma =1\)—once again showing a phase transition occurring in the interval of \(0.9 \le \gamma \le 1\). Each data point averages the results of 100 simulations. Other parameters are set to the same values as the previous figure.
