Abstract
Mating preferences can show extreme variation within and among individuals even when sensory inputs are conserved. This variation is a result of changes associated with evaluative mechanisms that assign positive, neutral, or negative hedonic value to stimuli-that is, label them as attractive, uninteresting, or unattractive. There is widespread behavioral evidence for differences in genes, environmental cues, or social experience leading to marked changes in the hedonic value of stimuli. Evaluation is accomplished through an array of mechanisms that are readily modifiable through genetic changes or environmental inputs, and that may often result in the rapid acquisition or loss of behavioral preferences. Reversals in preference arising from "flips" in hedonic value may be quite common. Incorporating such discontinuous changes into models of preference evolution may illuminate our understanding of processes like trait diversification, sexual conflict, and sympatric speciation.