192 M. M. Garver— Periodic Character 
plest possible element of thought would probably — wi 
least one period of maximum activity, ae more 
processes would require two, three, or e higher ia / 
of that number. According to pe perannts by Burekhardt,* 
Professor Donders, and many — the time soe og by an 
intelligent person to perceive and to will is about 51, of a 
second. ‘To illustrate, take an pe al from Burekhardt.* 
After allowing for the time required to traverse all of the 
nerves and for the latent period of the muscles, there still 
remains about of a second for the cerebral operations. 
When the signal was “> by a bell and the answer require 
a movement of t , the percentage of the time required 
for the different speniions was found to be as follows: 
Acoustic 6 per cent. 
Brain 62.“ 
Spinal cord 4 ‘i 
ervou smission 92 tk 
Latent period of muscles Can 
he mean value for the time required from “ear to hand” 
was 0°169”, of which 0°105” or sixty-two per cent was taken 
up by the mental operation involved. From this it will be 
seen that “quick as thought” is after all not so very quick. 
Similar results were obtained by — r.¢ In our experiments 
(see pine nen ene for June, 1878, p. 4 16), the “reaction period” 
from ear to hand varied from 071327” to 01651’. The latter 
atin is my own ‘reaction period ;” and if sixty per cent of 
the time was consumed in the cerebral operation it takes zy 
of a second for me to perceive and w 
The foregoing results were shintaad by answering to an eXx- 
pected and known signal; however, if a dilemma is introduced, 
offering a choice, the time required i is considerably lengthened, 
and the lengthening is greater as the mental Lapiaaees are 
more complex. Professor Donders{ made some experiments 
in which the answer was required by the left ees when the 
psychological processes involved. That is, it took of a 
second longer than if the signal was ao given in the same 
ue and sie aaa the same ans By poner three 
ed Soe Die Gai cleueiniathe Diagnostik der Nervenkrankheiten, Leipzig, 
1875 
+ See Foster s bri derse 6 p. 5 
¢ Donder; ete pi sbbechiiy Processe; Reichert und du Bois Ray- 
mond’s peti: 1868, p. 6 
