Developing gestures for no and yes

Yes and no, or acceptance and refusal, are widespread communicative skills that are common across cultures. Although nodding and shaking the head are common ways to express these seemingly simple responses, these gestures develop later than others such as pointing. We analyzed diary observations from eight infants to investigate the origins of these gestures, why they develop later than other early gestures, and why nodding the head to indicate yes develops later than shaking the head for no. We found that young infants were able to shake their heads side-to-side, but they did not use this movement to communicate refusals at first. Infants had difficulty learning the nodding movement, but they could perform the physical movement before using it to communicate yes. These gestures developed along different trajectories with shaking the head for no emerging between 13 and 15 months and nodding for yes between 16 and 18 months.