CONCLUkSION. 280 



not unexpected, but was known beforehand, the physio- 

 logical time proved to be much shorter ; in the case 

 of the sense of sight it was only from 0*07 to 0*11 of 

 a second. From this it follows that, in the case of 

 excitement the advent of which is expected, the brain 

 fulfils its work much more quickly. 



Certain experiments made by Donders are yet more 

 mteresting. A person was instructed to make a signal, 

 sometimes with the right hand, sometimes with the 

 left, according as a gentle irritant applied to the skin 

 was felt in one place or the other. If the place was 

 known, the signal succeeded the irritant after an in- 

 terval of 0'205 of a second, but if the place was not 

 known, only after an interval of 0-272 of a second. The 

 psychological act of reflection, as to where the irritant 

 occurred, and that of the corresponding choice of the 

 hand occupied, therefore, a period of 0*067 of a second. 



The physiological time in the case of the sense of 

 sight was somewhat dependent on colour ; white light 

 was always noticed somewhat sooner than red. If the 

 observer knew the colour which he was to see, he gave 

 the signal sooner than when this was not the case and 

 he had first to reflect as to what he had seen before he 

 gave the signal. In such experiments, the observer 

 always forms a preconception of the colour which he 

 expects to see. If the colour when it becomes obser- 

 vable corresponds with that w^hich he expected, the 

 reaction in the observer takes place sooner than when 

 this is not the case. 



Similar observations were made in the case of the 

 sense of hearing : the recognition of any sound heard 

 follows sooner when it is known beforehand what sound 

 is to be heard than when this is not the case. 



