458 



SCIENCE, 



[Vol. VI., No. 146. 



The foregoing, as has been stated, is only a 

 brief summary of the contents of this report, 

 which is given in an abridged form in Nature, and 

 will doubtless hereafter be published in full by the 

 association. The facts which it presents disclose 

 in the people of this aboriginal Switzerland quali- 

 ties much above the average, and should lead to 

 further inquiry into their history and character- 

 istics. 



SOME REACTION-TIME STUDIES. 



The study of reaction times derives a great in- 

 terest and importance from the fact that by this 

 means another bond of relation between mind 

 and matter becomes apparent. All material actions 

 require time. Mental actions as well, from the 

 perception of a sensation to the highest expression 

 of the intellect that offers itself to experimental 

 investigation, also occupy an appreciable amount 

 of time. This mental time is not constant as the 

 time of a falling body in space, but is affected by 

 slight variations in bodily and mental conditions. 



M. Beaunis ^ has studied the effect of one impor- 

 tant mental requisite, namely, expectation. The re- 

 actions were made to a visual sensation, and 36 

 persons besides himself (most of whom were med- 

 ical students) were experimented upon. A signal 

 (advertisement) was given, whereupon the subject 

 held himself in readiness for the flash of light, so 

 as to react by pressing the key as quickly as pos- 

 sible. The time between the signal and the flash 

 of light is the expectation time ; that between the 

 hght and the seeing of it, the reaction time. The 

 expectation time was varied from .3 sec. to 3 

 sec, and the following conclusions were reached : — 



(1) As others had ah-eady shown , the reaction 

 time is shorter if a signal is given than if it is not. 



(2) The longer the exiDCctation time, the shorter 

 the reaction time. The experiment may be com- 

 pared to the problem of finding an object in a 

 dark room by bringing the hght of a bull's-eye 

 lantern upon it. When there is no signal, that is, 

 when dhected to find the object without time to 

 get the lantern ready, it would evidently take 

 longer to find the object than it would if time 

 were given to get the lantern in position ; and the 

 longer this time, the quicker would the object be 

 found. The attention acts as the bull's-eye lan- 

 tern. 



(3) The difference between the minimum and 

 maximum times is greater than when a signal is 

 not given, and increases as the expectation time 

 increases. 



(4) The influence of several individual differ- 

 ences, etc., was evident. In two of the medical 



1 Revue philosophique, September, 1885. 



students the reactions were always slow. In 

 many it was very quick. M. Beaunis was the only 

 person who was accustomed to this kind of ex- 

 perimentation, and in his case a much smaller 

 percentage of experiments had to be thrown out 

 as faulty than in the others. The effect of health 

 was marked in one case. Feeling slightly indis- 

 posed in the morning, M. Beaunis's reaction time 

 was .37 sec, i.e., abnormally slow. In the after- 

 noon it was .222 sec, showing that the normal 

 condition was returning. Two hours later it was 

 normal (.160 sec). 



An extremely interesting research is that of 

 Guiccordi and Ranzi,^ in which they compare the 

 reaction time to a sound impression in normal per- 

 sons with the same in patients suffering from 

 auditory hallucinations. The reaction time is ob- 

 tained somewhat in this way. The making of 

 the sound which serves as the stimulus sets into 

 motion a chronoscope, which the subject stops, as 

 soon as the sound is heard, by pressing an electric 

 key. In this way the following table, giving in 

 seconds the time necessary for hearing the sound, 

 was prepared : — 



Normal. Hallucinated.. 



Average of 10 shortest reactions out of 50 

 Average variation .... 



Average of remaining 40 reactions - 

 Average variation ----- 

 Average of all 50 reactions 



Minimum time 



Maximum time 



.1012 



.0947 



.0033 



.0046 



.1259 



.1408 



.0132 



.0206 



,1135 



.1175 



.1731 



.2287 



Taking the mean of the 10 shortest reactions, or 

 comparing the minimum reaction time, we see 

 that those suffering from hallucination are quicker 

 in their perception of sound ; and this difference 

 must be ascribed to morbid irritability of these 

 centres of apperception. On the other hand, the 

 other averages, and especially the average diver- 

 gence from the mean reaction time, i.e. , the average 

 variation, and the maximum time, show that nor- 

 mal persons can command a steadiness and regu- 

 larity of the attention, which is impossible in those 

 afflicted with sound hallucinations. 



In many cases the reaction time is and must be 

 studied under rather artificial conditions. This 

 circumstance is apt to weaken inferences drawn 

 from such studies to similar processes in normal 

 mental activity. In a recent study ^ of the time 

 necessary for recognizing letters, numbers, colors, 

 etc, this difficulty has been successfully overcome. 

 Small letters were fastened to a revolving drum, 

 and looked at through a sht of variable width in 

 a screen held before the letters. The letters are 



1 Revue philosophique, September, 1885. 



2 " Ueber die zeit der erkennung und benennung von 

 schriftzeiohen, bildern und farben," by J. M. Cottell. Phi- 

 losophiche studien (Wundt), vol. ii., No. 4. Leipzig. 1885» 

 The work was done in the psychophysical laboratory of 

 Johns Hopkins university. 



