Boyd-Richerson model: conformist bias, direct bias (payoff), and frequency-dependent selection
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Boyd-Richerson cultural transmission: Frequency of variant A after one generation: p' = p + D(p) + α·s·p(1-p), where D(p) = β·p(1-p)(p-½) is the conformist bias (S-shaped). Conformist bias (β > 0): common variants are favored, stabilizing majority and creating an unstable interior equilibrium at p=½. Direct/payoff bias (α > 0): variant A has fitness advantage s. Genetic drift causes stochastic fixation in finite populations. The interplay produces rich dynamics: runaway conformism, bias amplification, and cultural canalization.