Signal Detection and Animal Communication

Publisher Summary This chapter provides an introduction to signal detection theory and its applications in psychophysics, and the objective is to identify general principles for the study of adaptations in animal communication. These principles can clarify the properties of signals that affect a receiver's performance. It also suggests ways to extend the theory to the classification, as well as detection of signals. To apprehend the essential features of signal detection theory, it helps to consider a simple situation. Suppose an individual listens for a conspecific vocalization characterized by some feature, such as a particular frequency. In this case, the signal has a single feature, a particular frequency, which varies along a single dimension, its intensity. The earliest application of signal detection theory to a behavioral problem was the determination of human sensory thresholds. Detectability is a measure of a receiver's ability to separate a signal from background stimulation; the analogous measure of ability to separate two signals is discriminability. Signal detection theory makes it clear that any receiver's performance in detecting or discriminating signals has limits. Although in many situations it is reasonable to assume that an animal's task involves no more than detection of an appropriate signal, in others some classification of a stimulus is essential. Signal detection theory describes decisions based on the outputs of perceptual channels. Detection and discrimination, the focus of discussion so far, suggest that the perceptual channels under consideration are sensory receptors and their immediate neural connections. Signal detection theory suggests ways that receivers and signalers could coevolve. Signal detection theory involves a level of abstraction unfamiliar in field studies of animal communication. In all of these ways, signal detection theory can advance our understanding of both the physiology and the evolution of communication.