264 'Journal of Comparative Neurology ami Psychology. 



describablc as to the difference of brightness of the two boxes and 

 satisfactory in its results. I cannot too strongly urge, from my 

 present point of view, the avoidance of cardboards as means of 

 testing visual discrimination. The conditions of many of my ex- 

 periments are practically indescribable so far as absolute value of 

 illumination is concerned, yet, as I now see it, they might perfectly 

 well have been describable with a fair degree of accuracy. 



TABLE 1.3. 



Relation of Age to Ability to Discriminate on the Basis of Difference 



IN Illumination, and to the Capacity for Improvement of 



Visual Discrimination. 



Having now tested the first of the two important factors in the 

 the acquisition of the white-black discrimination habit, namely, 

 ability to gain visual discriminating power (the educability of 

 white-light vision), we must turn to the second factor and in- 

 quire whether associative memory changes with age. 



It occurred to me that since the labyrinth habit, as conclusively 

 proved by Professor Watsoii^^ for the white rat, depends more 



"Watson, J. B. Kinsestlietic and Orgauic Sensations : Their Role in the 

 Reactions of the White Rat to the Maze. Psychol. Rev. Mon. Siipp., vol. 8, 

 no. 2, 1907. vi -)- 100 pp. 



