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 |
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.
III. INTERPRETATION OF RESULTS.
We may say provisionally that the change from a tactual stimulation of one kind to a tactual stimulation of another kind tends to lengthen subjectively the interval which the two limit. If we apply the same generalization to the other sensorial realms, we discover that it agrees with the general results obtained by Meumann[15] in investigating the effects of intensity changes upon auditory time, and also with the results obtained by Schumann[16] in investigations with stimulations addressed alternately to one ear and to the other. Meumann reports also that the change from stimulation of one sense to stimulation of another subjectively lengthens the corresponding interval.
What, then, are the factors, introduced by the change, which produce this lengthening effect? The results of introspection on the part of some of the subjects of our experiments furnish the clue which may enable us to construct a working hypothesis.
Many of the subjects visualize a time line in the form of a curve. In each case of this kind the introduction of a change, either in intensity or location, if large enough to produce an effect on the time estimation, produced a distortion on the part of the curve corresponding to the interval affected. All of the subjects employed in the experiments of Group 2 were distinctly conscious of the change in attention from one point to another, as the two were stimulated successively, and three of them, Hy, Hs and P, thought of something passing from one point to the other, the representation being described as partly muscular and partly visual. Subjects Mr and B visualized the two hands, and consciously transferred the attention from one part of the visual image to the other. Subject Mr had a constant tendency to make eye movements in the direction of the change. Subject P detected these eye movements a few times, but subject B was never conscious of anything of the kind.
All of the subjects except R were conscious of more or less of a strain, which varied during the intervals, and was by some felt to be largely a tension of the chest and other muscles, while others felt it rather indefinitely as a 'strain of attention.' The characteristics of this tension feeling were almost always different in the second interval from those in the first, the tension being usually felt to be more constant in the second interval. In experiments of the third group a higher degree of tension was felt in awaiting a light tap than in awaiting a heavy one.