The Sound of Contagious Laughter

Hearing people laugh often triggers laughter in listeners, but why do some laughs spread while others fall flat? Researchers have described the acoustic structure of laughter, but little is known about how acoustic features contribute to laughter contagiousness. Using a citizen science approach, we built an online platform where individuals could upload laughs that they found contagious and rate laughs that others had submitted. This approach resulted in 149 real-world laughs, which were rated by 1509 listeners. Acoustic analysis revealed that several features predicted contagiousness, including a faster burst rate, higher and more variable fundamental frequency (perceived as pitch), increased spectral center of gravity (linked to voice brightness), and lower entropy (less randomness). Additionally, listeners rated laughs as more contagious if they perceived the laughing person as belonging to their own cultural group. These findings demonstrate that both specific acoustic features and perceived group membership are associated with laughter contagiousness.