256 The Dancing Mouse 



weeks. It is safe, therefore, to conclude from the results 

 which have been obtained that a white-black or black-white 

 discrimination habit may persist during an interval of from 

 two to eight weeks of disuse, but that such a habit is seldom 

 perfect after more than four weeks. 



The measurements of memory which were made in con- 

 nection with color discrimination experiments are markedly 

 different from those which were obtained in the brightness 

 tests. As might have been anticipated (?), in view of the 

 extreme difficulty with which the dancer learns to discrimi- 

 nate colors, the habit of discriminating between qualitatively 

 different visual conditions does not persist very long. I have 

 never obtained evidence of a perfect habit after an interval 

 of more than two weeks, and usually, as is apparent from 

 Table 48, the tests indicated very imperfect memory at the 

 end of that interval. It seems probable that even in these 

 so-called color tests discrimination is partly by brightness 

 difference, and that the imperfection of the habit and its 

 short duration are due to the fact that the basis of discrimi- 

 nation is inadequate. This is the only explanation which I 

 have to offer for the difference which has been demonstrated 

 to exist between the duration of brightness discrimination 

 habits and color discrimination habits. 



The duration of a discrimination habit having been meas- 

 ured with a fair degree of accuracy, I undertook the task of 

 ascertaining whether training whose results have wholly 

 disappeared, so far as memory tests are in question, influences 

 the re-acquisition of the same habit. Can a habit be re-ac- 

 quired with greater facility than it was originally acquired ? 

 Is re-learning easier than learning? To obtain an answer 

 to the question which may be asked in these different forms, 

 ten individuals were experimented with in accordance with 

 a method whose chief features are now to be stated. In 



