Chimpanzees laugh differently if they're being tickled than if they're playing with each other, and we might be seeing something like that here, involuntary laughter, tickling laughter, being different from social laughter.
Nad naeravad kõdistamise peale teistmoodi kui üksteisega mängides. Siin näeme midagi sarnast: spontaanne naer, mis kaasneb kõdistamisega, on suhtlemisnaerust erinev. Ka akustiliselt siin suur erinevus.