In iambic measures similarly beaten out there is likewise no acceleration nor retardation apparent in the progress of the tapping.  The temporal differentiation of alternate measures is of the same extent as in the preceding group, namely, 1.000:0.991. the proportional quantitative values of the measure and its constituent intervals, taken in series of ten successive repetitions, are as follow: 

TABLE XXXVII.

Quantity I II III IV V VI VII VIII IX X Measure, 1.000 0.979 1.000 0.979 1.020 0.979 0.979 1.020 0.979 0.979 1st Int., 1.000 0.941 0.941 1.000 1.000 0.941 8.082 0.941 0.941 0.941 2d Int., 1.000 1.000 1.032 0.967 1.032 1.000 1.000 1.032 1.000 0.967

The alternation of greater and less duration in the rhythm groups is due to a variation in the time-value of the second interval only, the index of average change in the first member being zero.  That is, the greater index of instability again attaches to that element which receives the stress.  Though this holds true throughout these experiments, the amount of difference here is misleading, since on account of the smaller absolute value of the first interval the proportional amount of change within it which passes unrecorded is greater than in the case of the second interval.

In general, the larger temporal variations of the trochaic and iambic rhythm forms are too slight to be significant when taken individually.  The evidence of rhythmical treatment in such a series of reactions, which is strongly marked in the unaccented form, nevertheless receives reinforcement from these inconsiderable but harmonious results.

The proportional values of the variations in alternate measures for accented and unaccented elements are given in the following table, in which the figures for the trochaic and iambic forms are combined: 

TABLE XXXVIII.

  Interval I II III IV V VI VII VIII IX X
  Accented, 1.000 1.000 1.083 1.000 1.041 1.000 1.083 1.000 1.041 1.000
  Unacc. 1.000 1.000 1.000 1.035 1.071 1.000 0.964 1.000 1.000 1.000

It is perhaps worthy of note that in this table a still higher rhythmical synthesis of regular form appears in the accented elements if the figures be taken in series of four consecutive pairs of reactions.

In the group of triple rhythms next taken up—­the dactylic, the amphibrachic and the anapaestic—­each type presents an increase in the duration of the unit group between the beginning and end of the series, but without any regular curve connecting these terms.  Neither the average results nor those of the individual subjects show anywhere a decrease of duration in the progress of the tapping.  The proportional results for each of the three rhythm forms, and their averages, are given in the following table.