In order to get comprehensive qualitative results as rapidly as possible, a three-second standard was adopted in the succeeding work and only one compared interval, also three seconds, was given, although the subject was ignorant of that fact—­the method being thus similar to that adopted later for the final experiments of Group 2, described above.  Six types of tests were given, the order of stimulation in the different types being SSS, WWW, SSW, WWS, SWW and WSS, the subject always knowing which order to expect.  For each of the six types one hundred tests were made on one subject and one hundred and five on another, in sets of five tests of each type, the sets being taken in varied order, so that possible contrast effect should be avoided.  The results were practically the same, however, in whatever order the sets were taken, no contrast effect being discernible.

The total number of judgments of CT, longer, equal, and shorter, is given in Table VIII.  The experiments on each subject consumed a number of experiment hours, scattered through several weeks, but the relative proportions of judgments on different days was in both cases similar to the total proportions.

TABLE VIII.

    ST=CT= 3.0 SECS.

Subject R, 100.              Subject P, 105. 
L    E    S     d             L    E    S     d
SSS   32   56   12   + 20     SSS   16   67   22   —  9
WWW   11   53   36   — 25     WWW   19   72   14   +  5
SSW    6   27   67   — 61     SSW   17   56   32   — 15
WWS   57   36    7   + 50     WWS   37   61    7   + 30
WSS   10   45   45   — 35     WSS    9   69   27   — 18
SWW    3   31   66   — 63     SWW    3   64   33   — 25

By the above table the absolute intensity of the stimulus is clearly shown to be an important factor in determining the constant error of judgment, since in both cases the change from SSS to WWW changed the sign of the constant error, although in opposite directions.  But the effect of the relative intensity is more obscure.  To discover more readily whether the introduction of a stronger or weaker stimulation promises a definite effect upon the estimation of the interval which precedes or follows it, the results are so arranged in Table IX. that reading downward in any pair shows the effect of a decrease in the intensity of (1) the first, (2) the second, (3) the third, and (4) all three stimulations.

TABLE IX.

Subject R. Subject P.

(1) SSS     + 20                —  6
WSS     — 35  — 55          — 18    — 12

SWW     — 63                — 25
WWW     — 25  — 38          +  5    + 30

(2) SSW     — 61                — 15
SWW     — 63  —  2          — 25    + 10

WSS     — 35                — 18