A Dynamical System Approach to Sign Language

This pilot study introduces methods from dynamical systems theory to the analysis of sign language, highlighting their potential to reveal patterns of stability and variability in linguistic signals. We present two complementary measures: local Lyapunov exponents, which indicate how sensitive sequences of linguistic units are to small changes, and topological entropy, which quantifies the overall temporal complexity (chaoticity) of the sign language. The methods are illustrated using a single sign language text, analysed at two levels, sentences and individual signs, measured both in numbers of signs or pseudosyllables and in seconds. Results show higher complexity and lower stability at the level of individual signs. Lyapunov exponents capture local fluctuations and sensitivity in linguistic structure, suggesting moments where planning or motor execution may influence production, while topological entropy reflects the broader organization and predictability of discourse. Together, these measures provide a dynamic, multi-level perspective on language organization, indicating how micro-level variability interacts with macro-level structure, and offering new insights into the temporal and structural dynamics of sign language communication.