The investigation followed these lines:  I. Movements of a single image; II.  Changes of color of a single image; III.  Movements of two images in the same and in different directions; IV.  Suppression of one of two images; V. Movements of a single image, the object having been moved during the exposure.

I. MOVEMENTS OF A SINGLE IMAGE.

The first table gives the time in seconds taken to move voluntarily a single image (of a colored square or disc) to the right, left, up or down, and in each case to restore it to its original position.  There were thirty movements of each kind for each of the six subjects, making one hundred and eighty for each direction and also for each return, the total of all movements being fourteen hundred and forty.  The distance to which the subjects moved the images was not fixed, but was in most cases about twelve inches.  The time was taken with a stop-watch, and includes the time between the word of command, ‘right,’ etc., of the director and the verbal report ‘now’ of the subject.  It includes, therefore, for each movement two reaction times.  The subject reported ‘now’ the instant the color reached, or appeared at, the designated place, not waiting for the completion of the shape which usually followed.  Two of the subjects (H. and K.) took much longer than the other four, their combined average time being almost exactly four times the combined average time of the other four.

TABLE I.

MOVEMENTS OF A SINGLE IMAGE.

30 Movements of Each Kind for Each Subject Average Time in Seconds.

To           To
Subjects  Right Return Left Return Up   Return Down Return Averages
B.        1.30         1.07        1.06        1.11        1.13
0.58        0.73        0.46        0.45        0.55

G.        1.44         1.15        0.99        0.82        1.10
0.92        0.89        0.76        0.57        0.78

H.        7.12         6.42        5.96        5.85        6.34
4.51        4.41        4.36        4.40        4.42

I.        1.28         1.34        1.62        1.47        1.43
0.67        0.62        0.86        0.72        0.72

J.        1.71         1.42        1.40        1.14        1.50
1.34        1.53        0.77        0.74        1.09

K.        4.81         4.64        3.29        3.28        4.01
2.40        2.71        1.91        1.56        2.14

Averages  2.95         2.67        2.39        2.23        2.59
1.72        1.82        1.52        1.41        1.62

NUMERICAL.

The general averages for the different movements show that movement to the right was hardest, to the left next; while movement downward was the easiest.  A marked exception is seen in I., for whom the upward movement was the hardest and movement to the right was the easiest.  J. found movement to the left hardest.  For the return movements, the general averages show that the return from the left is the hardest, from the right next; while from below is the easiest.  Here again I. found the return from above the hardest and from below the next hardest; while from the left was the easiest.