Laughing Response to Physical Stimuli

Laughing response to physical stimuli is a human universal. This pattern is observed in sighted, deaf and blind children. The physical and acoustic form of the laughing response is a combination of a characteristic facial expression [relaxed open mouth – sometimes called a “play face”] and vocalization [quick, shallow, staccato breathing].

The facial expression is observed early in human ontogeny and may be a mechanism to attract and maintain adult attention and investment in neonates. Recent experimental work documents tickle-induced laughter in great apes and human infants.

Acoustic analysis of ape and human infant vocalizations while being tickled suggests homology, i.e. descent from the last common ancestor, ( LCA), of apes and humans, as the phylogenetic source for similarities.