On Assertoric and Directive Signals and the Evolution of Dynamic Meaning

Basic speech-act distinctions apply quasi-universally across languages, but little attention has been paid so far to formally modelling the evolution of these. Even worse so, standard models of language evolution from evolutionary game theory deliver functionally ambiguous meanings: evolved meanings in Lewisean signalling games seem hybrids between assertions and directives. This has been noted by Lewis (1969) already, but has only recently received renewed attention (Huttegger, 2007; Blume and Board, 2011; Zollman, 2011). Contrary to previous modelling attempts this paper argues that a functional distinction in formal models should be based on criteria that linguistic typology uses to distinguish clause types cross-linguistically. The paper then offers two simple models that delineate assertoric and imperative meanings once by semantic denotation and once by pragmatic effect. The latter requires us to go beyond standard modelling techniques: in order to account for the dynamic meaning element of “giving a directive” we need a mechanism of co-evolving meanings and norms.