Yerkes and Dodson, Habit Formatioii. 



4^3 



Almost all of the mice used were between six and eight weeks 

 old at the beginning of their training. The exact age of each, 

 together with its number, is stated in table 2. This table shows 

 also the general classification of our experiments. They naturally 

 fall into three sets. These are designated by the roman numerals 



TABLE 2. 



Age in days, at the beginning of training, of each mouse, with a statement of the 



conditions of training. 



I, II, and III in the table, and will throughout the paper be referred 

 to as the experiments of set I, set II and set III. As is suggested 

 by the heading "condition of discrimination," at the top of the 

 first vertical column of table 2, these sets of experiments differ 

 from one another first of all as to condition of visual discrimination 

 or, more explicitly stated, in the amount by which the two electric 



