ACTION OF OPIUM ON PSYCHOLOGICAL REACTION TIME 21 



METHOD 



The experiments were made on the authors themselves and on 

 ten colleagues, making twelve normal subjects in all. 



The reaction time was measured by means of an improved 

 chronoscope devised by Prof. Knight Dunlap, which is a far more 

 accurate and convenient instrument than the old Hipp instru- 

 ment. The apparatuses to be described by Professor Dunlap 

 elsewhere (10). It consists essentially of a synchronous motor, 

 run on a tuning fork vibrating fifty times per second, and regis- 

 tering the time in units of 2 a or 1 /500 of a second, the dial-hand 

 of the chronoscope being controlled by an electro-magnetic clutch. 



The simple sound reaction was obtained by the experimentor 

 calling out a word or number into the speaking disc which started 

 the chronoscope and the subject responding with a set answer 

 as soon as possible through another speaking disc, thus stopping 

 the clock. The results were then recorded in terms of 2 tr or 

 1/500 of a second. It is needless to state that the subject and 

 experimentor were separated by a curtain in order to prevent their 

 seeing each other. 



The simple touch reaction was obtained in a similar manner. 

 The experimentor touched the hand of the subject behind a 

 curtain, the pressure of the touch starting the chronoscope going. 

 The subject responded as soon as he perceived the touch sensa- 

 tion by pressing a bulb or touching a key which immediately 

 stopped the clock. 



The simple light reflex was tested by the experimenter's 

 pressing a key and thus lighting an incandescent lamp behind a 

 white screen, the subject responding by pressing another key 

 which extinguished the light and stopped the chronoscope. 



In order to determine the more complex reaction time or asso- 

 ciation reaction time, various devices were tried, such as re- 

 sponse to certain words (noun and adjective, subject and predi- 

 cate, etc.), but none of these were found satisfactory for the 

 purpose in view. The most convenient and satisfactory method 

 was finally found to be the calculation of a mathematical prob- 

 lem. Two sets of problems were submitted to the subjects in 



