Gargalesis is a scientific term for a playful, heavy type of tickle that often induces laughter (like moving your fingers on the sole of someone’s foot). The term was coined in 1897 by psychologists Arthur Allin and G. Stanley Hall, who also coined the term knismesis, a feather-like type of tickling that often creates a sense of irritation (like that from an insect or parasite, for example).
