Wiley, R. H.   1994.   Errors, exaggeration, and deception in animal communication.   In L. Real (ed.), Behavioral mechanisms in ecology. University of Chicago Press, Chicago.   Chapter 7, pp. 157-189.


My contention in this chapter is that animals make mistakes and that this simple but neglected circumstance has deep implications for the evolution of animal communication. The possibility of error is explicitly incorporated into mathematical theories of communication and choice, in particular information theory, signal detection theory, and decision theory. Although the basic concepts of these theories are neither new nor complex, they have yet to be integrated into evolutionary theories of animal communication. An objective of this chapter, by expanding themes introduced earlier (Wiley 1983), is to show that these basic concepts provide explanations for the evolution of some fundamental features of communication. In particular, they can provide sufficient conditions for the evolution of exaggerated displays and for the evolutionary stability of deception. This approach also indicates that some of the parameters needed to understand the evolution of communication have been overlooked.


Errors by receivers, in the sense of evolutionarily inappropriate responses to signals, are likely to occur during communication at long range, in dense aggregations, or in the presence of deception. Such errors have major implications for the evolution of communication. For signals that cannot be completely distinguished by a receiver, there are four possible results of any decision to respond or not to respond to a signal: correct detection, missed detection, false alarm, and correct rejection.

In general the probabilities of these results cannot be independently adjusted by a receiver; in particular, criteria for response that increase the probability of correct detection also inevitably increase the probability of false alarm. The inherent discriminability of the signal, together with the probability and net advantage of each outcome, determines the expected utility of any criterion for response.

Maximizing the expected utility of a receiver's criterion can lead to adaptive gullibility (evolutionarily stable susceptibility to deception) or to adaptive fastidiousness (low responsiveness to signals). In the latter case, signalers must contend with increased uncertainty in the responses to a signal. Signalers in such situations can improve signaling efficiency by increasing the inherent discriminability of signals, often by exaggeration. Female choice of mates, as an example of adaptive fastidiousness, can result in such exaggeration of signals.

In general, explanations for the evolution of any receivers' performance, such as examples of female choice or evolutionarily stable susceptibility to deception, require evaluation of the expected utility of the receivers' criterion as well as the probability and inherent detectability of the signal.

[ENTIRE ARTICLE (.pdf file)]