This conclusively proves that the habit of turning in a certain direction or of choosing by position can be formed more readily than a habit which depends upon visual discrimination. A rough comparison justifies the statement that it takes from six to ten times as long for the dancer to learn to choose the white box as it does to learn to choose the box on the right. Since this is true, it is exceedingly important that the possibility of choice by position or direction of movement be excluded in the case of tests of brightness discrimination. To indicate how this was effectively accomplished in the experiments, the changes in the position of the cardboards made in the case of a standard set of white-black series are shown in Table 12. The number of the series, beginning at the top of the table with the two lettered preference series, is given in the first column at the left, the number of the tests at the top of the table, and the position of the white cardboard, left or right, is indicated below by the letters l (left) and r (right). TABLE 12 POSITION OF WHITE CARDBOARDS FOR A SET OF 150 TESTS SERIES 1 2 3 4 5 6 7 8 9 10 Preference A l r l r l r l r l r B r l r l r l r l r l 1 r l r l r l r l r l 2 l l r r l r l l r r 3 r r l r l l r l r l 4 l l l r r r l r r l 5 r l r l r l r l r l 6 l l r l r r l r l r 7 r l l l r r r l r l 8 r r l l r l r l r l 9 r r r l l l r l r l 10 l l l l r r r r l r 11 r l r r r l l l r l 12 r l r l r r l l r l 13 r l r l l l r r r l 14 l l l l r r r r l r 15 r l r r r l l l r l It is to be noted that in the case of each series of ten tests the white cardboard was on the left five times and on the right five times. Thus the establishment of a tendency in favor of one side was avoided. The irregularity of the changes in position rendered it impossible for the mouse to depend upon position in its choice. It is an interesting fact that the dancer quickly learns to choose correctly by position if the cardboards are alternately on the left box and on the right.