762 



SCIENCE. 



[N. S. Vol. III. No. 73. 



31EASUBIN0 HALLUCINATIONS. 



In Science, 1893, XXII, 353, attention 

 was called to a method of measuring the 

 intensities of hallucinations. The method 

 is, in brief, as follows : 



In an unsuspecting subject the stimulus 

 R under the condition P is used to produce 

 a sensation 8. The sensation is a function 

 of the stimulus, /S'=/ (jB), and is measured 

 by means of it. By means of appropriate 

 adjustment of the conditions P the sensa- 

 tion can be made to appear just the same 

 whether is present or not. 



When R is not present, the sensation is 

 called a hallucination ; let it be denoted by 

 the H, although the person experimented 

 upon does not distinguish sensation from 

 hallucination. We have thus in such cases 

 H=S, and likewise *S=/(-R), with R used 

 measure the intensity of the hallucination. 

 It is also evident that II=F (P), and like- 

 wise (a fact seldom fully regarded in psy- 

 chology) S=F(P). 



With this method Dr. C. E. Seashore has, 

 under my guidance, carried out measure- 

 ments of hallucinations and has just pub- 

 lished the results in the Studies from the Yale 

 Psychological Laboratory for 1895. As the 

 fundamental idea may interest others than 

 those reached by the Studies, I will state it 

 briefly here. 



It was at iirst intended to end every ex- 

 periment in a measurement according to an 

 absolute scale of units of energy, e. g., light 

 by reference to a standard som-ce of illumi- 

 nation or to a bolometer-reaction (Langley, 

 Mem. Nat. Acad. Sci., 1891, V, 7), sound in 

 units of atmospheric displacement (Wien, 

 Wied. Ann., 1889, XXXVI, 834), etc.; 

 but it was soon decided that it was prefer- 

 able to first explore the region of suggestion 

 and hallucination with convenient arbitrary 

 scales without waiting to reduce these scales 

 io standards. This course has been amply 

 justified by the results ; the proper methods 

 of producing hallucinations have been found 



for all the senses and the arbitrary scales 

 have been so arranged that future investi- 

 gators can repeat the experiments under 

 exactly the same conditions, merely chang- 

 ing the scale. To be sure, this latter step 

 is generally very expensive in many ways ; 

 in our case width of exploration was pre- 

 ferable to minuteness. 



A typical case of the application of the 

 method is found in measuring hallucina- 

 tions of sound. The person experimented 

 upon was placed in a quiet room and was 

 told that when a telegraph sounder clicked, 

 a very faint tone would be turned on, and 

 that this tone would be slowly increased in 

 intensity. As soon as he heard it, he was 

 to press a telegraph key. The experi- 

 menter in a distant room had a means of 

 producing a tone of any intensity in the 

 quiet room. The apparatus for producing 

 the tone consisted in an electric fork inter- 

 rupting the primary circuit of an in- 

 ductorium in the experiment room and a 

 telephone in the quiet room (unknown to 

 the subject), which was in connection with 

 the secondary coil of the inductorium. The 

 intensity of the tone depended on the dis- 

 tance between the two coils of the in- 

 ductorium ; this distance was recorded in 

 millimeters. 



In the first few experiments a tone would 

 be actualljr produced every time the sounder 

 clicked, but after that the tone was not 

 necessary. It was sufficient to click the 

 sounder in order to produce a pure hallu- 

 cination. 



The persons experimented on did not 

 know they were deceived, and said that 

 all tones were of the same intensity. The 

 real tone could be measured in its intensity, 

 and since the hallucination was of the 

 same intensity it was also indirectly meas- 

 ured. 



Similar experiments were made on other 

 senses. For example, in regard to touch, 

 a light pith ball would be dropped regularly 



