Reports experiment made to determine the liminal values of different kinds of stimuli to the perception of rotation. The apparatus for securing rotation of S, described by Dodge was used with modifications initiating three kinds of stimulus-forms to rotation: a succession of five and ten degree movements with sudden onset and constant angular velocity, ten degree rotary movements approximating in angular acceleration and deceleration a true sine wave, and a succession of movements of greater angular extent in which the arithmetical acceleration was approximately constant for twenty degrees of rotation.The sensory data which enter into the perception of rotation is derived not only from the mechanism of the vestibule, but also from vision, audition, kinaesthesis, muscular strains, articular and dermal sensations, eye-movements, and changing configuration of pressures. In preliminary experiments it was possible to single out certain factors in the auditory receptor-field well enough to make sure that the illusion of rotation may be produced by movement of the auditory field when S is kept stationary.In the main series of experiments the stimulus-form of even rotation with sudden onset yielded a threshold value of approximately two degrees per second. The stimulus form of harmonic oscillations in sine waves of acceleration and deceleration tended to reduce the threshold below that required for direct rotation. Except for one unusually sensitive S, uniform arithmetical acceleration presented unfavorable conditions for the perception of rotation. From Psych Bulletin 20:09:00889. (PsycINFO Database Record (c) 2006 APA, all rights reserved)