From context to code: Shared information constrains the evolution of optimal codes
James Winters, Olivier Morin · Proceedings of the 12th International Conference on the Evolution of Language (Evolang12) · 2018
We communicate by means of coded information, contained in spoken words, written signs, or gestures.A code is a set of reliable associations between signals and meanings used to facilitate information transfer (Scott-Phillips, 2014).The amount of information that can be extracted from a code depends on its stability (the regularity of a signal-meaning mapping), and on whether the set of signalmeaning associations form an optimal configuration.A code is optimal when it reaches a tradeoff between two constraints.First, it contains the relevant information that the Recipient is supposed to extract from it (informativeness).Second, it presents this information in a compressible format, using mappings with a minimal description length (compressibility).Optimal codes are therefore the most compressible set of signal-meaning mappings capable of identifying the intended meaning in context (Kirby et al., 2015).Optimal codes help facilitate successful communication, but are not indispensable.Efficient communication can happen even with an unstable and weak code -because it makes use of information that is contextual as opposed to encoded (Piantadosi et al., 2012).Context, in this sense, is information external to a code which is relevant for reducing uncertainty about a Messenger's intended meaning.This contextual information can be retrieved from the common environment that communicators share; it can be stored in memory; or it can be inferred from a combination of these sources (Clark & Brennan, 1991).Only when the context is sufficiently rich to allow for some information transfer to take place, do optimal codes emerge to fill and enrich expressive gaps in communication (Bybee, 2010).We test the hypothesis that the informational distance between a Messenger and a Recipient (i.e., the amount of shared information) acts as a