WHAT ARE CONVENTIONAL SIGNALS

Confusion over the validity of 'conventional signalling' may have resu lted at least in part because it has been used to refer to different c oncepts. The main aim of this paper is to expose the source of this co nfusion, not to prescribe a particular solution. Two key current sense s of conventional signals are identified: (1) as strategic correlates of quality (or, more generally, of the parameter about which informati on is contained in the signal's message); (2) as signals whose design is arbitrarily related to their message. The sometimes difficult relat ionships between these two senses and other concepts in the signalling literature (assessment signals, strategic choice handicaps, direct in dicators, revealing handicaps) are explored. It is concluded that two separate but important distinctions have been used to characterize con ventional signals (first, whether or not signals allow strategic choic e, and, second, whether signalling costs are intrinsic to the signal's production), and that these remain of significance to the understandi ng of signal design. The paper concentrates mainly on signalling betwe en parties with conflicting evolutionary interests, but briefly shows how these concepts may relate to signalling systems with no conflict o f interest.