Why Complex Signals Matter, Sometimes

Animal signals commonly consist of multiple components-say a sound and a display-and students of signaling have offered many perceptual and cognitive explanations for why compound signals should be more effective. Yet, the economic benefits that receivers obtain by following multiple signal components remain unclear. Superficially, it would seem that a single discriminable difference should be sufficient to discriminate between underlying states, such as high-quality versus low-quality mates. This chapter asks when receivers can benefit by responding to combinations of signals. While there are many situations in which it is best to follow the single most reliable signal and ignore others, our model suggests that it can pay to follow signal combinations when these combinations indicate the occurrence of a rare event. This chapter develops the logic of this confirmation of rare events hypothesis of multiple signal use and discusses the implications of this idea for future studies of signaling.