A ticklish situation

Socrates. Galileo. Darwin. What did these geniuses have in common,
besidesmangy beards? All three pondered one of the universe's profound
mysteries: Why do we laugh when we're tickled?

While the answer still isn't clear, University of California
psychologist Christine Harris, Ph.D., has solved a small piece of the
puzzle. Ticklish laughter, she reports, doesn't require the presence of
another person. That may not seem like a major revelation. But since
people can't tickle themselves, many experts insisted that tickling
required interpersonal contact.

Harris, instead, believed ticklish laughter is more like a reflex.
But her theory seemed impossible to test--until she devised Mechanical
Meg, a robotic arm designed to look like a tickling machine. Thus
equipped, Harris blindfolded research subjects and left them alone with
Meg. But while the participants thought they were being tickled by a
machine, the culprit was actually an assistant hiding under a table. The
subjects giggled and squirmed anyway, a finding that supports Harris's
view that tickling doesn't depend on social contact. But did the subjects
guffaw because they were being tickled, or because the idea of being
tickled by a robot is funny?

ILLUSTRATION