Abstract

Recent research has shown different forms of yawn modulation, both in terms of the conditions associated with a variation of its frequencies and in terms of its physiological and pathological mechanisms. However, the discussion about its potential functions is still open, and new hypotheses are still emerging in literature. In particular, several hypotheses have been advanced, each of which attributes a primary role to a physiological (respiratory, arousal-related, thermoregulatory and linked to blood cortisol levels) or social-communicative function. This review provides a synthesis of empirical results and theories, highlighting the difficulty in tracing the complexities of yawning back to a singular functional explanation.