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This eBook from the Gutenberg Project consists of approximately 678 pages of information about Harvard Psychological Studies, Volume 1.
WWS + 50 + 85 + 30 — 48
(3) SSS     + 20                —  6
SSW     — 61  — 81          — 15    —  7
WWS     + 50                + 30
WWW     — 25  — 75          +  5    — 25
(4) SSS     + 20                —  6
WWW     — 15  — 35          +  5    + 11

There seems at first sight to be no uniformity about these results.  Decreasing the first stimulation in the first case increases, in the second case diminishes, the comparative length of the first interval.  We get a similar result in the decreasing of the second stimulation.  In the case of the third stimulation only does the decrease produce a uniform result.  If, however, we neglect the first pair of (3), we observe that in the other cases the effect of a difference between the two stimulations is to lengthen the interval which they limit.  The fact that both subjects make the same exception is, however, striking and suggestive of doubt.  These results were obtained in the first year’s work, and to test their validity the experiment was repeated at the beginning of the present year on three subjects, fifty series being taken from each, with the results given in Table X.

TABLE X.

ST = 3.0 secs. = CT.

Subject Mm. Subject A. Subject D.

S   E   L     d        S   E   L     d       S   E   L     d
SSS   24  13  13  — 11        7  30  13  +  6      10  31   9  —  1
WSS   33   9   8  — 25       20  24   6  — 14      17  27   6  — 11
SSW   19  15  16  —  3       23  16  11  — 12      10  31   9* —  1
WWW   19  12  19     0       13  26  11  —  2       1  40   9  +  8
SWW   18  30   2  — 16       23  21   6* — 17       7  38   5  —  2
WWS   13  16  21  +  8       12  30   8  —  4      15  25  10  —  5

Transcriber’s Note:  Original “16” changed to “6”, “19” to “9”.

Analysis of this table shows that in every case a difference between the intensities of the first and second taps lengthens the first interval in comparative estimation.  In the case of subject Mm a difference in the intensities of the second and third taps lengthens the second interval subjectively.  But in the cases of the other two subjects the difference shortens the interval in varying degrees.

The intensity difference established for the purposes of these experiments was not great, being less than that established for the work on the first two subjects, and therefore the fact that these results are less decided than those of the first work was not unexpected.  The results are, however, very clear, and show that the lengthening effect of a difference in intensity of the stimulations limiting an interval has its general application only to the first interval, being sometimes reversed in the second.  From the combined results we find, further, that a uniform change in the intensity of three stimulations is capable of reversing the direction of the constant error, an intensity change in a given direction changing the error from positive to negative for some subjects, and from negative to positive for others.

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