A positive feedback is established and both trait and preference are magnified. 8.5.1 Genetic correlation of trait and preference -Empirical studies have examined patterns of geographical variation in trait and preference or select on a trait and measure a correlated evolutionary response in the preference. Sons' intensity correlated with the fathers' and daughters of red males preferred red males and daughters of dull males showed no preference. Mate choice involves communication which is costly and a costly ornament can not be used as the sole evidence for the evolution of female preference. Women with more symmetrical breasts are more likely to have children.
Preference is indicated by olfactory cues in the urine.
8.7 Interacting forces -Direct selection, runaway selection and selection for good genes are not mutually exclusive. Single sexual ornaments have high FA 2. Female guppy allowed to choose between two males. Focal female then constrained and allowed to observe model female consorting with unpreferred male and not with the preferred male. Focal female allowed to interact with male guppies again, this time chose previously unpreferred male.