Direct selection for a single preference. This figure shows the strength of direct selection against female preference (ãp,0) as male trait frequency increases from 0 – 1. Each line represents direct selection for a different combination of female preference frequency (P) and cost (γ) – the solid black line indicates P=.01, γ=.01; solid gray indicates P=.01, γ=.1; dashed black indicates P=.5, γ=.01; dashed grey indicates P=.5, γ=.1. For all simulations, α=5; changing preference strength did not change the shape of the cost curve, but only scaled up the strength of selection against preference. Direct selection always acts against preferences, except when male traits are absent or fixed, in which case, ap,0=0.