Figure 3.

Illustration of the evolution of individual perceived quality p_i, through the genetically determined cognitive bias d_i = p_i − q_i, from individual-based simulation of populations similar to those illustrated in Fig. 2. Panel (A) shows evolution of mean and SD of p_i = q_i + d_i over the generations in a population with groups of size g = 2, with true qualities q₁ = 1, q₂ = 1 (i.e., all individuals have true quality 1). The mutation rate for alleles for d_i is 0.05 and the mutant increment is normally distributed with an SD of 0.04. The dashed line is the prediction from Eq. (17). Panel (B) shows the bias d_i, as a function of the mean quality $\overline{q}$ in the group, for a population with groups of size g = 2 and with true qualities selected randomly at the start of a generation from the set {0.00, 0.25, 0.50, 0.75, 1.00}. The dashed line shows the prediction from Eq. (17) for each group composition in the final simulated generation. The mutation rate per allele for d_i is 0.001 with SD of mutant increments of 0.04. Other parameters are as in Fig. 1.