124 



The Dancing Mouse 



TABLE 14 



RESULTS OF WEBER'S LAW EXPERIMENTS 

 Brightness vision 



guished from a variable of 9.4 hefners (.53 difference), for 

 the percentage of errors was only 20. But in the case of a 

 difference of .36 in the illuminations lack of discrimination 

 is indicated by 36 per cent of errors. A difference of .46 

 gave a frequency of error so close to the required 25 (26 per 

 cent) that I accepted the result as a satisfactory determination 

 of the just perceivable difference for the 20 hefner standard 

 and proceeded to experiment with another standard value. 



