Why synonymy is rare: Fitness is in the speaker

Abstract

Pure synonymy is rare. By contrast, homonymy is common in languages. Human avoidance of synonymy is plausibly innate, as theorists of differing persuasions have claimed. Innate dispositions to synonymy and homonymy are modelled here, in relation to alternative roles of speaking and hearing in determining fitness. In the computer model, linguistic signs are acquired via different genetically determined strategies, variously (in)tolerant to synonymy or homonymy. The model defines communicative success as the probability of a speaker getting a message across to a hearer; interpretive success is the probability of a hearer correctly interpreting a speaker's signal. Communicative and interpretive success are compared as bases for reproductive fitness. When communicative success is the basis for fitness, a genotype evolves which is averse to synonymy, while tolerating homonymy. Conversely, when interpretive success is the basis for fitness, a genotype evolves which is averse to homonymy, while tolerating synonymy.