Tickled pink?

Abstract

What is tickling and why can’t we tickle ourselves? In order to tackle the tickle problem, Harris and Christenfeld developed a wholly new piece of apparatus: the tickle machine 1 Harris C.R. Can a machine tickle?. Psychonomic Bull. Rev. 1999; 6: 504-510 Crossref PubMed Scopus (24) Google Scholar . This is a robotic hand attached via a flexible hose to a piece of vibrating equipment. Experimental participants sit in front of it, blindfold and barefooted, and their foot is tickled by what they believe to be the robot. In fact, they are being tickled by hand by the same research assistant who tickles them in the ‘human tickling’ control condition. This ensures that the only difference between the two conditions is the participant’s belief about who is tickling them – a person or a machine. Subjects report that the tickling sensation is as strong when they think they are being tickled by the machine and when they are being tickled by the human hand. Thus, you may not be able to tickle yourself, but a machine certainly can tickle you. This finding provides evidence against a widely held account of tickling, the interpersonal communication hypothesis. According to the interpersonal view, tickling is fundamentally a form of friendly communication between human beings. To produce the tickling sensation, stimulation must come from another individual, and that is why you can’t tickle yourself. But if a machine (or what you think is a machine) can tickle you, tickling must be more like a startle reflex than a form of communication; that is, it is an involuntary response to an external stimulus. Of course, it may also be that postmodern humans are willing to accept robots as communicating agents. Many cognitive scientists would not be too surprised about that – in fact, they’d be tickled pink.