Interest in the question of when and how species recognition and mate preferences emerge in animals with strong species-typical predispositions has faded since the time of the classical ethologists. In its place, the role of plasticity has surfaced as a central emphasis in the study of animal behavior. Here, I step back and examine the origin and execution of sexual behavior in a tropical frog for which auditory predispositions are key. These experiments challenge assumptions about behavioral development, auditory perception, and stereotyped behavior. First, I illustrate when and how a sex- and speciestypical behavior---conspecific phonotaxis---emerges during development. This study demonstrates that phonotaxis, presumably restricted to mature females, is present in both sexes early in postmetamorphic development---potentially long before such behavior might serve an adaptive function. I place this result in the context of hypotheses regarding the development of learned versus non-learned behaviors, and in light of the potential for perception to be altered by physiological changes occurring concomitantly with ontogeny. Next, I describe a set of dynamic mate choice studies that highlight how decision-making in a relatively simple system is more flexible, and less stereotyped, than was previously assumed. Results here show that frogs temporally update their mate choice decisions in a moment-to-moment fashion as advertisement signals change in real time. By decomposing the decision-making process, I determine the stimulus parameters essential for commitment to an initial phonotactic approach. These studies are followed up by experiments that reveal a high level of individual variation in female choosiness during mate choice. Lastly, I describe a mate choice study that revealed categorical perception in frogs, the first "lower" vertebrate now known to exhibit a perceptual mode previously considered a hallmark of "higher" organisms. Collectively, I make the following arguments: (1) constraints on sensory systems play a larger role in shaping behavior than is generally appreciated, irrespective of the involvement of learning; (2) unstudied sources of variation may contribute significantly to the raw material for sexual selection; and (3) phonotaxis in anurans amphibians is not the simple, stereotyped behavior that has been suggested of it in the past.
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