occurred only once, with one subject. Similarly, Table 3 shows that the average extent of the movement, when it did occur, was less for all six subjects when under relaxation. It will be noticed that no measure of variability is included in the tables. The results were highly variable, and such a measure would probably have given no indication that the differences found were significant. Their significance was tested, however, in another way. An average was taken for each condition, for each sitting. In cases where both conditions were given at a sitting the average for the relaxed condition was compared with the normal average for the same sitting; in the other cases, the comparison was between the averages for two successive sittings. Table 4 shows the total number of such comparisons for each subject in each series, and the number of cases where the extent of movement was less for the relaxed than the normal condition. In drawing up these averages zero cases were excluded. When all the relaxed reactions for a given sitting showed zero movement, however, the sitting was included in the table. Inspection of this table leaves no doubt of the significance of the difference in extent of movement resulting from the two conditions. TABLE 4 NUMBER OF CASES SHOWING MOVEMENT LESS FOR RElaxed than Reaction-Time.-In general the reaction-time was longer with relaxation than without. Table 5 shows that for Subjects A, B, C, and E the average time is longer with relaxation than with the normal condition; and the fact that this is a significant difference appears from Table 6. For Subjects D and F however the case is different. Table 5 shows that for Subject D the average reaction-time is longer with the normal condition than with relaxation, and for Subject F the average, though longer for the relaxed condition TABLE 6 NUMBER OF CASES SHOWING REACTION-TIME LONGER FOR RELAXED THAN FOR NORMAL CONDITION 1 The number of cases represented is less than in the table for extent of movement (3), partly because there are no reaction-times corresponding to zero movement and partly because, in a few cases, defects in the graphs made it impossible to calculate the time. in Series Ia, is longer for the normal in Series Ib. A closer analysis of the results is necessary to show whether these averages represent consistent tendencies. In the first series taken, Subject F gave results similar to those of other subjects. The average reaction-time was longer with relaxation than without, and the difference was consistent for all of the separate comparisons. In the second series, which differed from the first in that the stimulus was increased in duration and slightly decreased in strength, the average reaction-time was longer for the normal condition. Table 6 shows that this relation holds for three of the four separate comparisons. The frequency distributions shown in Figs. 1 and 2 throw further light on the subject. The FIG. 1. Frequency distribution of reaction-times, Subject F, Series Ia. FIG. 2. Frequency distribution of reaction-times, Subject F, Series Ib. values for the relaxed condition are distributed quite similarly in the two series; but in Series Ib there occurs with the normal condition a small group of peculiarly long times. Without these, the normal average would be shorter than the relaxed. An analysis of the results for Subject D gave similar results. In each case it was a small group of very long reaction-times, appearing late in the series with the normal condition, which made the average for this condition longer than that for relaxation. FIG. 3. Frequency distribution of reaction-time, Subject D, Series I. In the effort to explain these peculiarly long reactiontimes it was necessary to take into account both the graphic records and the written reports of the subjects. These reports showed certain characteristics to be peculiar to Subjects D, F, and C. It has been mentioned that, in the preliminary series, certain individuals were found from whom no available stimulus could elicit a very extended arm movement. Subjects D and F throughout, and Subject C in Series Ia, retained this characteristically restricted movement. They also retained a mode of response peculiar to them, a tendency to react with a widespread stiffening of the muscles without extended movement of any part of the body. Observation of this reaction suggested that it represented movements vigorously initiated by numerous muscles but checked almost immediately by the contraction of their antagonists. Certain other considerations suggested that this tendency might have been related to the lengthened reaction-times under discussion. The study of the graphic records of individual reactions showed a correlation between the length of the reaction-time and the form of the arm movement. For these subjects the typical reaction curve for the normal condition shows two distinct peaks, clearly indicating a double movement. In some cases, however, there is a single peak, and in others the first peak is followed by another so small as to be indistinguishable from a mechanical rebound from the first movement. With the reaction curves classified as double, single, and doubtful, their corresponding reactiontimes were listed as normal or lengthened, on the basis already determined from inspection of their frequency distribution. The result is shown in Table 7. No figures are given for Subject F in Series Ia; in this series all the curves were double and there were no lengthened reaction-times. The close correlation between the long reaction-times and the single form of curve suggests that the lengthened times are to be accounted for by the absence of the first movement represented in the double curve; and this in turn may be due to a contraction of anatagonistic muscles giving, momentarily, complete inhibition of the upward movement. In the case of the double curve this inhibition would seem to have come later and to have given place in turn to the persisting tendency to upward movement. This explanation was partly con |