Psychology. — "On Subjective Rhytlunimtion." 83- F. F. Hazelhoff 

 and Miss Hei, ken Wiersma. (Communicated by Prof. E. D. 



Wiehsma). 



(Communicaled at the meeting of May 26, 1923). 



Rhythmical perceptions, corresponding to rhythmical phenomena 

 in the outer world, are at all times produced in nninberless varieties 

 by the riiythmical play of ail sorts of piiysical and physiological 

 processes. (Succession of day uiul night, of summer and winter, the 

 heart-beat, the respiration, music etc.). 



However, our perceptions are not always (rue reproductions of 

 the reality round about us, as is borne out t)y many sensory 

 illusions. The present authors are disposed to class among these 

 illusions of perception also the pecidiar |)henomeiion that we can 

 perceive rhythmically a series of absolutely equal and regularly 

 successi\e stimuli, which phenomenon has been termed "subjective 

 Rhythmisation". 



We purpose to discuss this phenomenon from a |)sychological 

 view-point. 



It was especially Bc)I,ton(1) and Meumann(2) who pointed out the 

 fact that regulai' series of auditory stimuli, i.e. amlitory stimuli, 

 precisely uniform quantitatively as well as qualitatively, and suc- 

 ceeding one another after equal intervals, can be perceived rhyth- 

 mically, in any event when the rale of succession lies within certain 

 bounds. KoFFKA (3) demonstrated the same with regard to visual 

 stimuli, satisfying the same conditions. 



This rhythmical perception of regular stimuli, however, is not 

 restricted to visual-, and auditory sensations. The same rhylhmisation 

 also occurs in the department of touch. This we were able to 

 demonstrate by a simple experiment. 



Experiment: A regularly rotating axis is provided with a pointer that slightly 

 touches the motionless hand of the observer at every revolution. Tlie hand receives 

 at every time precisely the same tick after precisely equal pauses (the rate of 

 rotation may be regulated at will). The whole apparatus is hidden from the eye 

 of the observer by a screen ; neither can he see the pointer toucliing his hand. 



