Tickling Healthy Subjects

Aim: Abnormal response to tickle stimulation has been demonstrated in schizophrenia and somatoform pain disorders. The aim of this study was to characterize the responses of healthy subjects to identical tickle stimuli applied by different individuals: 1) an experiments, and 2) the subjects themselves, with attention to the type of device employed, the age and gender of the subject, the surface (palm, dorsum of hand) and side of the subject to which the stimulus is applied. Method: Tickle was applied using two different pieces of apparatus: 1) a spring-loaded pointer, and 2) an artist's paint brush. 42 healthy subjects were randomly, sequentially stimulated on the palmar and dorsal surfaces of both hands. Tickle was graded using 0-10 scale. Data were predominantly analysed using ANOV As. Results: For the pointer, the main effects of identity of the applier (F 1,41 = 19.3, p < 0.001), surface (F 1,41 = 19.3, p<0.001) and hand (F 1,41 = 5.2, p = 0.029) were significant. Ticklishness was greater when the stimulation was applied by the experiments, to the palm of the hand and to the right hand. For the brush, none of the main effects or interactions reached a conventional level of significance. Age and gender did not have significant effect. Conclusions: In healthy subjects, the existence of a perceptual difference when identical tickle stimuli are applied by an experimenter or the subject themselves, was confirmed. The results will inform future studies using this tickle paradigm.