Facial expressions, smile types, and self-report during humour, tickle, and pain

The nature of ticklish smiling and the possible emotional state that accompanies it have been pondered since the ancient Greeks. The present study is arguably the first to systematically examine facial behaviour and self-reports of emotion in response to tickling. Using a within-participants design, 84 participants' responses to being tickled were compared to their responses when experiencing a painful stimulus and their responses to comedy. Overall results for both self-report and facial action coding showed that the tickle condition elicited both pleasure and displeasure. Facial action during tickling included Duchenne smiles plus movements associated with negative emotions. Results suggest that tickle-induced smiling can be dissociated from positive affect. Accounts of tickle are discussed.