Experience of sexual signals can alter mate preferences and influence the course of sexual selection. Here, we examine patterns of experience-mediated plasticity in mate preferences that can arise in response to variation in the composition of mates in the environment. We use these patterns to test hypotheses about potential sources of selection favouring experience-mediated plasticity. We manipulated signal experience of female Enchenopa treehoppers (Hemiptera: Membracidae) in a vibrational playback experiment with the following treatments: silence; two types of non-preferred signal; preferred signals; and a mixture of preferred and non-preferred signals. This experiment revealed plasticity in mate preference selectivity, with greatest selectivity in the mixed signal treatment, followed by the preferred signal treatment. We found no plasticity in peak preference. These results suggest that females have been selected to adjust preference selectivity according to the variability of potential mates in their social environment, as well as to the presence/absence of preferred mates. We discuss how experience-mediated plasticity in mate preferences can influence the strength of selection on male signals and can result in evolutionary dynamics between variation in preferences and signals that either promote the maintenance of variation or facilitate rapid trait fixation.