Preliminary Observations on Tickling Oneself

Abstract

WHY is it that most people cannot tickle themselves? Darwin observed that “from the fact that a child can hardly tickle itself, or in a much less degree than when tickled by another person, it seems that the precise point to be touched must not be known”¹. (There may be differences between man and other primates. The Kelloggs observed that their chimpanzee Gua was “frequently observed in the process of tickling herself and laughing as a result”2.) But this hypothesis seems prima facie incorrect, or at least inadequate, as most children can be tickled even when they know where and when the tickle stimulus is to be applied. No experimental work appears to have been reported on this question, and Darwin's interest was primarily centred on the biological value of ticklishness and laughter. The problem is perhaps not trivial; evidently knowledge of some sort is necessary for the cancellation of the ticklish sensation, and it has been shown that cancellation of other signals (for example, those that arise from voluntary movement of the eyes) seems to be produced by self-generated “command” signals rather than by external feed-back^3,4. Does a similar mechanism exist for the tactile system ? Another question is whether pain is subject to the same type of control; if so, there could be practical clinical applications.