238 



SCIEIfCE. 



[^OL. VIII., No. 



Wundt, it is a little longer than tlie distinction 

 time, and, like it, is very much affected by differ- 

 ent conditions of mind, and varies largely in dif- 

 ferent individuals. It, too, can be complicated by 

 making the choice between three, four, or several 

 modes of reaction. 



Only one more type of reaction time will be 

 here mentioned. It is called an ' association time,' 

 and is measured as follows : A word is called, and 

 simultaneous with the call the clock-work is set in 

 motion. As soon as possible after the word is 

 heard, the subject answers by uttering the first 

 word associated with the call-word that suggests 

 itself to him. By subtracting from this time the 

 time necessary for the hearing of the first word 

 and the utterance of the second,we have the time 

 involved in the process of association, or the ' as- 

 sociation time.' This is a very much more compli- 

 cated process, and naturally occupies a longer 

 time, — about f of a second. It differs largely in 

 different states of mind and in individuals. It 

 can be complicated by restricting the kind of 

 words allowable as associations. For example, 

 only words related to the call-word as part to 

 whole may be aUowed. We thus test what may 

 be termed the ' suggestiveness,' or co-ordination, 

 of one's mental furniture. 



All these reaction times have been measured in 

 laboratories under somewhat artificial conditions, 

 and with the aid of more or less elaborate appara- 

 tus. It has long been desirable to avoid this arti- 

 ficiality, and thus make the inferences from such 

 experiments to similar processes in our daily 

 thought more certain and immediate, and to sim- 

 plify the apparatus so that the demonstration of 

 these mental times may be easy and inexpensive. 

 It is to describe an attempt at solving these diffi- 

 culties with reference to a few types of reaction 

 times, that I devote this article. 



My method is a very simple one. We require 

 delicate apparatus, because we have to measure 

 very small fractions of a second ; and this, in turn, 

 is necessary, because we measure but a single 

 reaction time at once. By measuring a long series 

 of successive reactions we can dispense with deli- 

 cate time apparatus ; for the eiTor involved by 

 such neglect will be divided among the whole 

 series, and will thus not appreciably affect the 

 value of the average reaction time. For our pur- 

 poses a small clock or a watch beating quarter- 

 seconds, as a rule, is sufficiently accurate. One 

 can readily count four to the second, and the pro- 

 cess can be made still easier by tallying off the 

 ' tens ' by pencil-marks or on one's fingers. It is 

 advisable, in counting, to emphasize alternate num- 

 bers ; thus, one, two, three, four, five, six, etc. 

 We shall find incidentally that the conditions 



suitable for such experimentation are uncon- 

 strained and natural. The method is applicable 

 to all the kinds of reaction times above described. 



1. Simple reaction times. — Here I have but a 

 single experiment to offer. On one occasion I im- 

 posed sufficiently on the good nature of an even- 

 ing company of about eighteen persons to ask them 

 to arrange themselves in a circle, each one stand- 

 ing with the forefinger of one hand resting upon 

 the shoulder of the person before him. At a given 

 signal, one of the party gently pressed with his 

 finger upon his neighbor's shoulder, who in turn 

 communicated the impression as soon as he felt it 

 to the shoulder of the one before him ; and so on 

 around the circle. The impression made four or 

 five complete revolutions, and the time was taken 

 to the nearest quarter of a second. By dividing 

 the time by the product of the number of revolu- 

 tions of the impression into the number of persons, 

 one obtains the average simple reaction time for 

 a touch impression. A little drill would be 

 necessary before the time would be constant, inas- 

 much as a miscellaneous set of persons do not 

 readily act together without rehearsals. My time 

 was about 4 of a second, but it would evidently 

 have been shorter could I have repeated the ex-" 

 periment. It is recommended as a useful evening 

 amusement. There is one point more : if the reac- 

 tion lime of any j)articular individual is desired, 

 one has only to subtract from the average time of 

 one revolution of a circle in which he forms a 

 member, the time of a revolution of the impres- 

 sion in which he is absent. 



2. Distinction time. — The apparatus consists of 

 a clock ticking quarter-seconds (a stop-watch is 

 much more convenient), and several packs of ordi- 

 nary playing-cards. To begin with a very simple 

 case : Take a single pack of cards ; throw out all 

 the face cards, and you have forty cards left, of 

 which twenty are red, and twenty black. Shuffle 

 these well together. Let the assistant be ready 

 with the clock close to his ear to give you a signal 

 when to begin, and to count the ticks. The ' one ' 

 by which he begins his counting is a good signal.^ 

 The moment you hear the word ' one,' you throw 

 the first of the forty cards upon the table, and con- 

 tinue to do so with the rest, distributing them into 

 two heaps. As you throw the last card, you call 

 ' Done ! ' w^hereupon the assistant closes his count- 

 ing. The cards must be divided without any plan 

 between the two heaps — about as a chance arrange- 

 ment would divide them. The time consumed in 

 this operation divided by the number of cards will 

 be spoken of as the ' throwing time.' 



What naturally suggests itself as the next opera- 



1 It is advisable to prepare the subject for the signal by 

 previously calling, ' Ready ! ' 



