giving 1916; follow the dotted path from _c_ to _h_, the straight line
from _h_ to _i_, the dotted path from _i_ to _k_, the straight line
from _k_ to _l_, the dotted path from _l_ to _m_, the straight lines
from _m_ to _n_ and _n_ to _g_, the dotted path from _g_ to _m_, the
straight line from _m_ to _l_, the dotted path from _l_ to _k_, the
straight line from _k_ to _i_, the dotted path from _i_ to _n_, and the
straight line from _h_ to _c_, when a second reading is taken, which
was in this case, 1806. Divide the difference of these two readings,
1100 mm., by the length of _cd_, 119 mm., and the result is 9.1 mm., or
the mean error (mean variation).
It will be noted that this method gives the sum of the errors from
the mean line _cd;_ that is, the same result would be obtained if the
tracing-point were (1) carried from _c_ around all the area below _cd_,
and this area were calculated as before; (2) carried from _c_ around
all the area above _cd_ and the area measured as in other cases; and
(3) these two results added and averaged.
To apply the method for _ab_, or constant error computation, to _cd_
should give equal readings at _c_ or a 0 mean error, a result evidently
incorrect in the record selected.
After averaging results by the planimeter, the collection of data has
been arranged by months; the record for one month only can be presented
here, but the method of tabulation is the same throughout.
Each figure given for N, M, c and v, in the accompanying typical table
for the month of May, 1904 (pages 495-499), is the average from 20 or
50 lines, ruled as already shown, Fig. _D_.
RESULTS
It is necessary to observe that the limits of space imposed on the
writer preclude all but the barest outline of the deductions to be
drawn from the investigation, and to this fact is due whatever of
dogmatism is inherent in the argument; for it is manifestly impossible
to present all the material, and the writer asks, then, the indulgence
of the reader when he claims to have impartially examined and presented
the evidence.
HAND MOVEMENTS
Simple movements
Lines 14 cm. long.
TYPICAL SERIES FOR THE MONTH
Key.
v = mean error.
R.H. = right hand.
R.F. = right foot.
E.O. = eyes open.
si. = simple motion
N = normal line.
Unit = 1 mm.
L.H. = left hand.
L.F. = left foot.
E.C. = eyes closed.
co. = compound motion.
M = mean line.
b = beats per minute.
c = constant error.
See Beats per minute.
Day. Subject. Key. 20 30 40 50 60 70 80 100 120
6 Hylan. N 10 10.5 11 11 10 10 10 12 10
L.F.E.O. M 16.1 13.5 12.1 13.8 13.1 10.0 10.0 11.2 12.5
c +6.1 +3.0 +1.1 +2.8 +3.1 0.0 0.0 -0.8 +2.5
v 2.8 3.5 1.9 0.9 1.6 4.6 2.0 2.7 1.2
140 160 180 200
12 10 11 11
12.0 6.1 11.0 14.21
0.0 -3.9 0.0 +3.2
1.0 1.3 2.1 4.0
Hylan. N 10 11 10 12 10 12 11 11 11
L.F.E.C. M 8.9 10.5 10.9 11.4 13.1 10.3 11.8 13.1 13.9
c -1.1 -0.5 +0.9 -0.6 +3.1 -1.3 +0.8 +2.1 +2.9
v 2.7 6.4 2.2 1.4 2.7 1.6 2.3 1.6 4.9
11 11.5 11 11
15.8 11.0 15.0 17.8
+4.8 -0.5 +4.0 +6.8
2.9 2.3 2.3 2.5
George. N 10.5 10 10 10 10 10 10 10 11
L.F.E.O. M 14.6 9.7 7.1 6.4 7.7 8.3 8.0 10.0 11.0
c +4.1 -0.3 -2.9 -3.6 -2.3 -1.7 -2.O 0.0 0.0
v 2.1 1.6 1.8 2.3 0.8 0.7 1.4 1.7 0.8
10 10 11 11
9.0 10.0 8.0 12.5
-1.0 0.0 -2.0 +1.5
1.0 1.3 1.6 0.4
George. N 10 9 9 10 11 9.5 9 10 8
L.F.E.C. M 11.7 9.2 10.2 12.6 13.2 11.5 12.2 6.6 5.0
c +1.7 +0.2 +1.2 +2.6 +2.2 +2.0 +3.2 -3.4 -3.0
v 2.0 2.9 2.5 0.7 0.5 1.0 0.8 2.0 4.1
10 9 9 10
8.0 7.6 8.0 11.0
-2.0 -1.4 -1.0 +1.0
3.1 2.5 2.1 3.7
Moore. N 10 10 10 10 11 11 11 10 10
L.F.E.O. M 15.7 18.8 17.7 16.7 18.3 18.5 16.5 15.6 16.0
c +5.7 +8.8 +7.7 +6.7 +7.3 +7.5 +5.5 +5.6 +6.0
v 3.5 3.8 1.1 0.8 3.6 2.1 2.7 0.6 2.4
10 11 10 10
16.2 16.3 16.4 18.8
+6.2 +5.3 +6.4 +3.8
0.5 3.5 2.2 3.8
N 10 10 10 10 11 10 10 9
Moore. M 19.6 15.3 15.3 14.3 14.9 13.5 6.7 13.4
L.F.E.C. c +9.6 +5.3 +5.3 +4.3 +3.9 +3.5 -3.3 +4.4
v 2.6 2.5 2.4 0.4 2.0 6.4 0.7 4.1
9.5 11 11 10 10.5
20.0 14.3 14.5 16.9 17.9
+10.5 +3.3 +3.5 +6.9 +7.4
2.6 3.8 1.1 3.1 2.8
N 10 10 9 10 10 9.5 10 10
9 Angier. M 13.6 12.5 11.6 11.6 11.5 11.7 13.0 12.9
R.F.E.O. c +3.6 +2.5 +2.6 +1.6 +1.5 +2.2 +3.0 +2.9
v 2.9 2.3 1.8 2.3 1.7 1.6 2.0 2.7
11 10 10 10 10
12.2 12.2 13.5 22.1 16.5
+1.2 +2.2 +3.5 +12.1 +6.5
3.3 1.5 1.5 6.7 1.5
N 10 10 10 9.5 10 9 10 10
Angier M 11.4 7.7 13.8 8.3 11.4 11.5 11.0 10.3
R.F.E.C. c +1.4 -2.3 +3.8 -1.2 +1.4 +2.5 +1.0 +0.3
v 4.8 1.3 3.0 2.6 1.4 1.7 1.8 1.7
140 beats
9 10 10 11 10 10
9.9 12.8 16.7 17.7 12.4 12.0
+0.9 +2.8 +6.7 +6.7 +2.4 +2.0
1.8 1.4 1.7 4.2 2.1 1.7
N 11 10 10 9 10 11 10 10
Huggins. M 12.5 8.5 12.6 9.7 9.7 16.6 15.7 18.7
R.F.E.O. c +1.5 -1.5 +2.6 +0.7 -0.3 +5.6 +5.7 +8.7
v 3.6 2.6 2.7 2.8 3.3 3.2 3.3 3.6
10 11 11 11 10
13.6 15.8 9.3 18.3 14.3
+3.6 +4.8 -0.7 +7.3 +4.3
3.1 2.7 2.9 3.8 3.0
N 11 8 10 10 11 10 10 10
Huggins. M 6.5 10.5 10.7 8.8 12.6 12.9 12.2 22.3
R.F.E.C. c -4.5 +2.5 +0.7 -1.2 +1.6 +2.9 +2.2 +12.3
v 1.4 2.1 1.8 1.6 3.7 3.1 2.0 4.1
10.5 10 10 10 10
9.9 21.8 12.0 12.5 16.3
-0.6 +11.8 +2.0 +2.5 +6.3
1.4 5.0 2.3 3.6 1.8
N 9 9 9 9 9.5 8 7 10
13 Lenfest. M 12.7 11.9 11.1 11.3 12.1 8.7 11.6 12.6
R.F.E.O. c +3.7 +2.9 +2.1 +2.3 +2.6 +0.7 +4.6 +2.6
v 3.7 2.4 1.9 2.3 2.8 0.2 2.8 2.1
10 10 9 8 10
9.0 8.6 11.7 7.0 11.8
-1.0 -1.4 +2.7 -1.0 +1.8
2.0 2.1 3.2 1.4 4.1
N 12 11 11 10 10 10.5 11 11
Lenfest. M 14.9 14.7 12.2 13.5 12.6 11.9 12.6 8.7
R.F.E.C. c +2.9 +3.7 +1.2 +3.5 +2.6 +1.4 +1.6 -2.3
v 3.3 2.2 3.5 3.5 3.2 3.0 2.6 1.7
11 11 10 10 10
9.1 8.9 8.4 14.1 6.9
-1.9 -3.1 -1.6 +4.1 -3.1
2.4 2.8 2.9 4.1 2.3
N 12 11 11 11 11 10 11 10
George. M 8.3 9.0 8.6 8.8 8.7 7.0 7.4 7.9
R.F.E.O. c -3.7 -2.0 -2.4 -2.2 -3.3 -3.0 -3.6 -2.1
v 5.0 3.3 2.3 0.1 3.3 2.9 2.4 3.1
11 10.5 11 10 10
6.8 9.7 9.0 5.8 11.0
-4.2 -0.8 -2.0 -4.2 +1.0
1.5 4.6 2.9 2.9 3.9
N 12 11 12 11 11 11 10.5 11
George. M 7.0 7.7 14.1 8.3 10.3 8.4 8.7 7.8
R.F.E.C. c -5.0 -3.3 +2.1 -2.7 -0.7 -2.6 -1.8 -3.2
v 2.5 2.6 2.4 3.7 2.9 2.3 1.6 2.1
10 10.5 11 10 10
6.4 10.0 9.0 7.9 7.3
-3.6 -0.5 -2.0 -2.1 -2.7
1.9 3.7 2.9 1.8 3.8
N 11 11 11 11 12 10 9 11
Moore. M 14.5 16.6 16.5 9.0 17.0 10.7 10.4 11.9
R.F.E.O. c +3.5 +5.6 +5.5 -2.0 +5.0 +0.7 +1.4 +0.9
v 1.7 2.2 1.9 1.8 1.3 2.2 2.6 2.2
10 10.0 10.5 11 9.5
11.5 12.5 12.5 15.1 12.6
+1.5 +2.5 +2.0 +4.1 +3.1
2.2 2.5 2.5 1.4 0.8
N 11 10 11 11 11 10 10 9
Moore. M 14.3 13.2 15.9 12.3 17.9 10.0 11.3 15.9
R.F.E.C. c +3.3 +3.2 +4.9 +1.3 +6.9 0.0 +1.3 +6.9
v 1.8 2.8 1.6 2.1 1.7 2.4 3.2 2.2
11 11.0 10 10 10
14.8 15.5 13.4 11.8 12.2
+3.8 +4.5 +3.4 +1.8 +2.2
2.7 1.4 2.2 1.8 2.2
N 11 11 10 11 10 10 10 11
16 Angier. M 14.3 13.5 9.3 14.4 14.1 9.5 15.1 12.7
R.F.E.O. c +3.3 +2.5 -0.7 +3.4 +4.1 -0.5 +5.1 +1.7
v 1.7 1.9 2.0 2.4 2.0 1.1 2.4 2.8
10 11 10 11 11
11.1 12.6 13.7 11.0 16.6
+1.1 +1.6 +3.7 0.0 +5.6
2.0 2.0 2.7 1.3 3.5
N 11 10 10 9 10 10.5 10 10
Angier. M 14.4 4.8 2.5 3.6 5.8 6.7 8.0 11.0
R.F.E.C. c +3.4 -5.2 -7.5 -5.4 -4.2 -3.8 -2.0 +1.0
v 3.2 2.7 2.3 3.6 2.7 2.3 1.3 2.8
11 10 11 11 11
13.5 11.1 13.9 10.1 11.0
+2.5 +1.1 +2.9 -0.9 0.0
2.8 1.4 2.4 1.8 2.2
N 97 97 98 97 98 99 97 98
Huggins. M 107.6 107.8 100.4 114.2 98.0 110.3 89.4 102.5
L.F.E.O. c +10.6 +10.8 +2.4 +17.2 0.0 +11.3 -7.6 +4.5
v 5.9 0.6 4.8 6.5 5.3 6.7 6.4 5.5
95 98 99 99 100
99.2 100.8 106.4 101.5 108.9
+4.2 +2.8 +7.4 +2.5 +8.9
7.8 6.0 4.7 7.0 12.7
N 97 98 100 97 95 95 99 99
Huggins. M 102.8 104.3 115.1 101.4 94.1 102.0 106.4 93.4
L.F.E.C. c +5.8 +6.3 +15.1 +4.4 -0.9 +7.0 +7.4 -5.6
v 5.8 8.6 10.8 9.9 7.9 10.4 8.1 6.8
97 98 99 99 100
87.7 98.7 108.4 97.7 110.8
-9.3 +0.7 +9.4 -1.3 +10.8
9.4 5.8 6.9 5.3 6.1
N 11 11 10 10 10 10 10 10
20 Lenfest. M 16.1 13.5 11.6 10.9 10.9 14.2 11.7 10.5
L.F.E.O. c +5.1 +2.5 +1.6 +0.9 +0.9 +4.2 +1.7 +0.5
v 2.8 3.0 3.0 3.0 1.2 1.9 1.0 1.6
11 10 11 11 10
12.4 11.1 12.2 8.7 12.9
+1.4 +1.1 +1.2 -2.3 +2.9
3.2 5.1 1.9 1.7 4.2
N 12 11 10 10 10 11 10 10
Lenfest. M 20.4 16.8 11.6 11.2 11.8 14.0 9.0 9.3
L.F.E.C. c +8.4 +5.8 +1.6 +1.2 +1.8 +3.0 -1.0 -0.7
v 2.5 3.6 3.0 1.9 1.6 2.0 3.0 1.2
10 10 11 11 10
6.2 10.0 8.5 5.1 8.3
-3.8 0.0 -1.5 -5.9 -1.7
1.9 0.3 1.8 1.7 0.8
N 98 97 94 98 98 97 98 98
George. M 104.0 100.4 102.6 99.3 105.1 111.1 101.9 100.5
L.F.E.O. c +6.0 +3.4 +8.6 +1.3 +7.1 +14.1 +3.9 +2.5
v 6.4 11.3 9.6 7.7 5.3 8.0 3.7 5.6
97 96 98 98 97
96.4 102.0 97.4 94.2 95.8
-0.6 +6.0 -0.6 -3.8 -1.2
5.7 5.7 9.1 7.8 3.6
N 98 97 94 97 97 98 98 97
George. M 93.6 81.2 94.7 92.7 104.2 99.3 93.4 89.6
L.F.E.C. c -4.4 -15.8 +0.7 -4.3 +7.2 +1.3 -4.6 -7.4
v 9.1 8.9 5.5 4.6 5.8 6.9 4.9 6.6
96 98 98 99 100
96.4 93.0 87.3 101.8 87.4
+0.4 -5.0 -9.7 +2.8 -12.6
7.8 4.8 7.7 5.6 5.7
N 97 99 98 97 96 96 97 98
Moore. M 106.1 106.9 105.2 103.0 104.7 108.6 102.7 106.9
L.F.E.O. c +9.1 +7.9 +7.2 +6.0 +8.7 +12.6 +5.7 +8.9
v 4.3 5.6 4.6 5.2 8.0 6.0 7.4 6.9
99 98 99 99 99
110.9 105.7 111.2 99.9 93.0
+11.9 +7.7 +12.2 +0.9 -6.0
4.8 9.0 4.7 11.4 1.8
N 96 97 97 97 96 97 96 97
Moore. M 119.2 79.8 87.3 79.6 81.6 91.2 96.5 106.2
L.F.E.C. c +23.2 -17.2 -9.7 -17.4 -14.4 -5.8 +0.5 +9.2
v 16.1 6.7 11.6 7.2 7.5 4.1 4.0 6.6
99 98 97 98 99
100.4 91.9 104.0 88.6 80.9
+1.4 -6.1 +7.0 -9.4 -18.1
4.0 6.1 5.4 6.6 8.2
N 98 97 95 96 96 97 99 97
23 Lenfest. M 105.7 110.8 97.4 93.8 97.8 100.2 99.9 92.9
L.F.E.O. c +7.7 +13.8 +2.4 -2.2 +1.8 +3.2 +0.9 -4.1
v 9.3 1.5 3.6 5.1 3.6 4.4 2.9 3.3
97 98 98 98 99
86.1 96.6 91.9 80.9 83.0
-10.9 -1.4 -6.1 -17.1 -16.0
6.7 5.0 8.2 6.0 7.8
N 96 94 96 96 96 94 96 97
Lenfest. M 111.3 95.0 98.3 101.7 101.7 110.1 98.8 79.0
L.F.E.C. c +15.3 +1.0 +2.3 +5.7 +5.7 +16.1 +2.8 -80.0
v 7.1 5.1 5.8 2.7 5.4 7.8 12.1 3.7
97 97 100 100 100
88.9 72.7 88.4 69.7 80.8
-8.1 -24.3 -11.6 -30.3 -19.2
5.6 8.0 7.4 8.4 7.0
N 96 97 96 96 98 98 97 97
Huggins. M 113.5 105.7 105.5 97.7 92.5 98.4 92.5 102.0
L.H.E.O. c +17.5 +8.7 +9.5 +1.7 -5.5 +0.4 -4.5 +5.0
v 4.2 2.4 3.6 5.0 3.5 3.1 4.2 5.8
95 98 98 99 97
95.0 112.3 104.5 108.7 95.7
0.0 +14.3 +6.5 +9.7 -1.3
4.7 6.4 5.8 7.1 4.4
N 98 97 97 97 97 99 99 97
Huggins. M 103.5 82.8 86.1 87.8 87.7 94.2 92.1 94.5
L.H.E.C. c +5.5 -14.2 -10.9 -9.2 -9.3 -4.8 -6.9 -2.5
v 8.4 6.7 5.4 3.5 6.7 5.4 6.0 5.8
97 97 98 98 96
99.9 111.5 101.3 113.7 95.1
+2.9 +14.5 +3.3 +15.7 -0.9
4.8 13.3 4.7 9.6 2.6
N 96 95 96 96 96 97 96
27 Lenfest. M 101.6 93.4 91.2 90.0 97.5 93.2 93.4
R.F.E.O. c +5.6 -1.6 -4.8 -6.0 +1.5 -3.8 -2.6
v 6.2 5.1 3.4 2.8 5.5 4.5 3.7
96 99 102 101 100
89.8 97.5 88.6 96.8 66.2
-6.2 -1.5 -13.4 -4.2 -33.8
5.5 3.6 4.3 4.9 8.1
N 96 96 97 97 97 98 98
Lenfest. M 103.8 101.2 94.0 100.3 96.4 101.2 105.0
R.F.E.C. c +7.8 +5.2 -3.0 +3.3 -2.6 +3.2 +7.0
v 6.2 7.4 4.5 3.8 3.5 4.7 2.4
95 98 100 99 100
78.0 98.5 88.8 85.1 65.8
-17.0 +0.5 -11.2 -13.9 -34.2
4.7 4.3 7.0 6.9 5.9
The records are averaged for nine subjects, three of them being
left-handed. For the right hand we find, for mean error, a reduced
error with visual control.
For constant errors, a similar result is apparent; when following the
eyes-closed curve one may note a large negative error 20-50 beats, and
a similar but larger positive error 70-160 beats, with a falling to a
negative error again at 200 beats.
This may be interpreted to mean a groping for the correct length of
line at the lower speeds when some time for reflective processes is
allowed, and an inhibitory effect on the motor discharge; later the
speed prevents this discrimination, and introspective testimony goes
to show that a mental conception of a barrier, beyond which one cannot
carry the pencil, is set up and kept more or less constant through the
help of the joint and muscular sensations. It would follow, then, that
this muscular stop is overestimated where reflection is not possible.
Finally, the falling-off of the length of the line is probably due to
physical inability to rule a line of the full length of 140 mm. at 200
beats per minute and an examination of some individual cases confirms
this opinion, for the lines may be started some distance away from the
origin apparently in order to end them at the correct point.
Curve inclinations are upward, for mean errors, with visual control,
while the eyes-closed records show no increase in error for the
increased speeds.
For constant errors, with visual control, there is a similar
inclination downward for both hands, with a 0 error at about 120 beats.
It should be noted that this opposite tendency in mean and constant
errors suggests that they should be kept separate in all computation.
The left-handed subjects have much better control of their left hand
than have the right-handed subjects, and they may dispense with visual
control to a large extent.
On the other hand, for right-hand records we find much the same
increase in irregularity and error for both left- and right-handed
subjects; they all must depend on visual control for reduction of
errors.
It follows that the non-visual control exerted by the left-handed
subjects on the right hand is as good or as great as for the
right-handed subjects; while they have the hand in which they may be
expected to excel under much better control.
It is not intended to present this as an argument for teaching
left-handedness, but it is certainly suggestive when considering the
question that ambidexterity be taught in early life.
It should be noted that two of the three left-handed subjects might be
expected, because of special training, to show marked manual dexterity,
while only one of the four right-handed subjects has had special
training along this line.
No extended discussion is appropriate here as to the question of what
portion of this extra ability of the left-handed subjects to react
accurately is due to practice and habit, _i. e._, is automatic, and
accomplished without reference to the sensory motor by-path to the
cerebral cortex; and on the other hand, as to whether the direct
sensory motor path via spinal cord or medulla is not cut off entirely.
For 140 mm. averages and free motion, we find in general
(1) a reduced error and greater uniformity of result at all speeds
where visual control is added, in the case of both mean and constant
errors and for all subjects;
(2) the mean errors for visual-control records show a rise along a
line whose equation is approximately _y_ = _px_, or the equation of a
straight line, where _p_ is an undetermined constant.
On the other hand,
(3) the eyes-closed mean errors show no increase or decrease in value
during the entire series;
(4) the constant errors for visual-control records show a drop from
positive errors to negative errors, along a line whose equation is
approximately _y_ = _qx_ or the equation of a straight line, where _q_
is an unknown constant, somewhat less in value than _p_ in the case of
mean errors; the constant error becomes 0 at about 120 beats;
(5) the eyes-closed constant errors follow the same equation for
left-handed subjects, using the left hand, but all other cases suggest
a curve of the parabolic form, having 0 constant errors at 60 and 180
beats and being convex upward.
Considering individual records for 14 cm.
A general survey of the charts suggests certain irregularities that
call for explanation, for there will be sudden large increases in
errors, that are explicable on the hypothesis that the subject has
temporarily lost control of the moving hand, that is, that fatigue is
to be noted.
While the purpose of the investigation has been to allow no lines to be
ruled while the subject was conscious of any such feeling, there being
a pause of any desired length to permit time for rest, it is to be
noted that a considerable amount of recorded data as to fatigue shows
that it is an unconscious or subconscious phenomena.
Further, the series of records have been arranged to occur from 20
to 200 beats and never in the reverse order, because of subjective
limitations, so it is reasonable to expect that during the period of
twenty minutes to one half an hour required for a series of records,
there will be lapses of volitional control entirely beyond the ken of
the subjects. It is to this cause rather than to pure chance that the
results will be attributed. With this exception, the individual records
show close agreement with their average.
The results obtained from a consideration of free hand-movements of 1,
10, and 14 cm. length are:
For 14 cm. lines
for the average of nine subjects:
The mean errors,
(1) increase with speed for eyes open;
(2) do not change in error with speed-change for eyes closed;
(3) visual control reduces errors for right hand, but does not for the
left;
(4) right-handed subjects alone gain from visual control.
The constant errors,
(1) decrease with speed in visual cases;
(2) increase with speed to the middle and then reduce to 200 beats for
eyes closed;
(3) left-handed subjects are more accurate for the left hand and can
dispense with visual control;
(4) all subjects need visual control for the right hand;
(5) left-handed subjects show less error throughout for non-visual.
For the individual cases,
the mean errors
(1) show evidences of loss of control or fatigue for some speeds, and
the average results are confirmed.
The constant errors show that the average deductions are confirmed.
Lines 10 cm. long:
Averages for seven subjects as regards mean errors have especial
interest for l.h.e.c. records, which alone show a rise of error with
speed-increase.
Noting that the records are overwhelmingly averages of right-handed
subjects (six to one), it is of interest to examine this record.
We may say, then, that for right-handed subjects, the voluntary control
for the right hand is not much improved by the introduction of visual
assistance; it is more marked for speeds of 100 beats or less than for
the high speeds. And in the latter case, it is under 10%; but when the
left hand is considered, a marked gain or 40 or 50% is apparent, when
the eyes are used except for the two lowest speeds.
As far as it is possible to offer any hypothesis from the few
facts tabulated, it may be said that right-handedness implies a
high development of muscular control, but slightly improved by the
introduction of the visual element, as far as the right hand is
concerned; but for the left hand muscular control comparable to the
right-hand control can be obtained only with visual control; in short,
I fail to find evidences of cross-education, where the visual element
is absent, nearer than about 50% of the mean error.
No clearly marked gain through visual control can be pointed to in
the case of constant errors; there is, to be sure, a slight gain in
steadiness and error-reduction, where eyes help in the case of both
hands, but not 5% in magnitude of the difference noted with mean errors.
Individual records show fatigue-points at 40 to 80 beats and again
above 140 beats, but there is no perceptible loss of control during a
series of lines ruled at only one speed.
It is apparent, when comparing with the 140 mm. records, that there is
no physiological reason why the subjects may not rule the full length
of a 10 cm. line at 200 beats, and the limit of movement for high
speeds is probably between 10 and 14 cm.
The constant errors are in general positive and only Me. shows a
tendency to underrule lines at high speeds.
For 10 cm. lines,
for the average record,
(1) the mean-error curve is horizontal for l.h.e.o., but otherwise
rises with speed-increase;
(2) visual control is a 10% gain for right hand and 40 to 50% for the
left, so right-handedness is prominent for the eyes-closed series;
(3) the constant-error curve for r.h.e.c. rises, but all others show
reduction of error as rate increases;
(4) visual-control gains are not over 5%.
The individual curves show,
for mean errors,
(1) marked-fatigue points for l.h.e.o;
(2) r.h.e.o. curve is horizontal, but all others rise;
(3) l.h.e.o. curve is about the same as r.h.e.o., but there is more
loss for non-visual series with left hand.
For constant errors,
(1) r.h.e.c. curve rises, but all others are horizontal;
(2) the eyes reduce errors especially for the left hand;
(3) overruling is prominent even at high speeds, for there is no
evidence that the lines are shortened at high speeds.
Lines 1 cm. long:
Averages are made for nine subjects, three being left-handed.
The eyes are effective in reducing mean errors and to a less extent for
constant errors.
A noteworthy feature of the constant-error record is that the errors
are positive with one exception, that of 20 beats with l.h.e.c. and
even this curve jumps rapidly above the 0 line.
In all cases the motor discharge is of sufficient magnitude to cause
overruling in cases of normal lines of one cm. The assistance afforded
by the eyes is not marked.
Certain evidence of an introspective character, that most of the
subjects offer, is to the effect that, "when I would do good, evil
is present with me"; that, where there is a decided feeling that the
muscular limit, if such a term be permitted, is exceeded, yet the
subject's will-power is not sufficient to inhibit the overruling; there
is a more or less vivid conscious error in the 10 mm. series for the
hands.
In regard to the relation of mean and constant errors, there is more
close uniformity than with the 140 mm. lines, but it is to be noted
that there is no comparison to be drawn between maximum or minimum
points; for example, at 100 beats the minimum points for r.h.e.o. agree
closely, but the maximum constant error matches the minimum mean error
at 100 beats for r.h.e.c.
We cannot predict, then, that a subject capable of closely ruling to
the normal will be able also to rule each line of the same length as
the rest of the series, or _vice versa_.
As in the case of mean errors in general note that subjects show a less
constant error and more regularity for their more dexterous member;
it is not true for the left hand that for left-handed subjects visual
control is a hindrance for accurate work; otherwise the same gain, by
use of the eyes, is to be noted for the rest of the records.
Individual records show close correspondence with the average of
results, and the latter may be considered fairly representative.
Almost the whole series shows the constant error positive, the most
consistent example being for J. with l.h.e.o.; this tendency to
overrun the 1 cm. lines is consistently uniform and has been elsewhere
commented on, so it may be left with the observation that the log shows
that the subjects were frequently conscious of this overruling, but
confessed inability to correct it.
Only in the case of Y. for the three left-handed subjects and for W.
among the six right-handed men does the left hand show less mean error
than the right hand, and all other cases show such an interweaving of
curves as to render it difficult to perceive any advantage that the
more dexterous hand possesses on the score of accuracy.
For constant errors:
For individual cases it is to be noted that for the left-handed
subjects J. is better for the right hand, Le. is indifferent, and Y.
prefers the left hand; while three of the six right-handed subjects
prefer the left hand and one is indifferent; thus giving still further
proof that a more dexterous hand is a fiction on the score of the right
or left-handed theory, when accuracy of straight-line movement is to be
considered.
For 1 cm. lines,
for the average, note
for the mean errors:
(1) visual control reduces errors;
(2) errors increase for eyes open, but decrease for eyes closed, as
speed increases when considering right hand, but left-hand errors are
constant;
(3) as left-handed subjects are better for r.h.e.o. than right-handed
subjects, but not for eyes closed, it is suggested that visual control
equalizes differences in the subject's less trained hand.
For constant errors:
(1) visual control reduces errors;
(2) curves are horizontal in all cases;
(3) all errors are positive, showing consistent overruling;
(4) as visual control of the left hand is a gain for right-handed but
a hindrance for the left-handed subjects, the more practised hand is
probably able to dispense with visual control, and depend largely on
the muscular sense.
Mean and constant errors are not comparable. For the individual
cases we find a corroboration of the above and for mean errors: more
dexterous hand does not excel, and evidence against ambidexterity is
conflicting; for constant errors: overruling is consciously done.
Constrained hand-movements for lines 14 and 1 cm. long and for the
weight, both accelerating and retarding the movement, are to be next
considered.
Constrained motions are of two general types as examined by the writer.
Series of the records for the hands were taken at 140 mm. and 10 mm.
bases with a weight hung on the finger or fingers of the hand under
investigation; in one series the weight acted as a pull or accelerating
effect on the ruled line and in the other series the weight was imposed
as a retarding effect, tending to restrain the movement of the hand.
This weight was in all cases 260 grams, this weight being chosen as of
sufficient amount to have a perceptible effect, but not large enough to
cause feelings of pain or fatigue in any case.
The average for seven subjects, three being left-handed, is as follows:
In general, the mean errors for the right hand are less, and less
variable as compared with the left hand. The left-hand records are very
close to the corresponding right-hand curves, especially the portions
of the eyes-closed records 20 to 120 beats.
This may be said for both mean and constant errors. In general, mean
errors are reduced, and curves are more nearly straight lines when the
weight is added; also the weight reduces constant errors, and gains
more regular records at all speeds. It is to be noted as a point of
unusual interest that there is no apparent shortening of the line ruled
when the weight is hung on the hand, for the negative errors are less,
not more when the weight is applied.
In general, then, the imposition of a weight that will be small enough
not to cause pain or fatigue shows that both mean and constant errors
are reduced; that the amount of error is less variable over the range
of speeds used; that the records show no retarding effect, but that
the subject is both able to move the hand just as far as without the
weight, and do it with much greater accuracy.
Individual records for 14 cm. and weight-retarding show a marked
reduction in both mean and constant errors, and a less marked gain
in uniformity in every case. This tends to confirm the introspective
opinion of W. subject that the imposition of a retarding weight tends
to reduce errors of both classes and to cause greater steadiness.
It should be added that there is evidence of an occasional letting-go
of voluntary control, so to speak, resulting in a large increase in
mean error, as already pointed out, or a large increase in negative
constant error, as shown on all individual records, and it would
seem then that the matter of cortical control is more vital and
indispensable for the restricted movements.
The effect of weight-retardation on visual records is to reduce the
error and steady the ruling of the less dexterous hand to a much more
marked degree than for the well-trained hand.
In the l.h.e.c. records the lack of corrective effect of visual
control is marked, as in the case of free movements, but the dip in
the curve at 30 to 70 is not noted in the free ruling and should be
considered as a distinct shortening due to weight-retardation before
discriminative processes have oriented the subject.
Without considering the accelerating weight-records in detail note that:
The effect of weights (less than that necessary to cause pain or
fatigue), either tending to accelerate or retard motions, is to reduce
both mean and constant errors and to render more uniform or more
uniformly increasing or decreasing such errors, except in the case
of l.h.e.c., where constant errors are greater positively with the
weight-pulling and greater negatively with the weight-retarding, than
for free motions; that is, the effect of the weight is natural, and
shows no signs of inhibition in this particular case.
There is no such marked fluctuation in error for the pull-records
as was noted for the weighted curves, and it is further noted that
the individual pull-records are more bunched or consolidated about
some mean than are the free-movement curves. This suggests that the
accelerating weight is a decided help for accuracy and regularity, and
it would seem to call for less voluntary control than for either of the
other movements.
Further, as the effect of pulling weights is to equalize the accuracy
of movement of the hands, the hypothesis is proposed that weights
either accelerating or retarding the movements of the hand tend to
equalize their accuracy or to promote ambidexterity as far as accuracy
of straight-line mean errors is concerned.
L.h.e.c. rise for Ha., are horizontal for J., W., and Y., and slope
downward for the other subjects, the net effect being a slight downward
slope. The loss of accuracy and regularity when the visual sense is
inhibited is to be noted in every case, it being especially marked for
Bo., Li., and W.
As compared with the r.h.e.c., there is not sufficient evidence to
lead to the conclusion that the right hand is a more accurate member
than the left, but on the contrary the left-hand record for non-visual
control is lower for both weighted series than is the right-hand curve.
Contrasting this with the eyes-open records for free and weighted
movements, the visually aided results show a greater accuracy and
regularity for the right hand.
This leads to a proposition that the greater dexterity on the line
of accuracy, of one hand, that is the right hand for right-handed
subjects, and the left hand for left-handed subjects, is a matter
of visual control and is in no sense due to the muscular sense or
to automatic action, for without eyes we are ambidextrous as far as
accuracy of linear movements is concerned; the proposition needs
careful scrutiny in application to the general question, but is held to
be correct within the range of experiments.
We are tempted to extend this matter somewhat in the following way,
by saying that there is no evidence deducible from this research that
there is hereditary preponderance of activity or accuracy of one hand
or one leg (as shown later) over its mate, and the baby is brought into
the world with an equal capacity of accuracy of both members.
It is, then, an evolutionary matter, not racial but individualistic,
and right-handedness or left-handedness is largely a development after
birth. Our system of education is responsible for the over-development
of one hand, and such a case as that of Dr. Anderson of the Yale
University Gymnasium, who in class demonstration cannot instantly tell
which hand is being used to actuate the chalk at the blackboard, is the
normal symmetrically developed man.
The school reform for ambidextrous training is radical enough, but
seems a logical conclusion of the argument. Apologies are appended for
driving the argument beyond the limits of the investigation, but it is
hoped that the enquiry is at least suggestive.
For 14 cm. lines,
weight-retarding movements:
For the average of nine subjects:
The weight reduces errors and promotes regularity in the case of both
mean and constant errors, nor does it tend to cause underruling, save
in the case of left-handed subjects for l.h.e.c. records. There is a
gain, in general, when the visual factor is introduced.
For mean errors,
(1) right-hand curves are horizontal, while the visual records show
increasing error and l.h.e.c. a reduction of errors;
(2) the right hand gives slightly better results;
(3) note that l.h.e.c. record is equally good for free or weighted
movements.
For constant errors,
(1) r.h.e.o. and l.h.e.o. curve downward, while both non-visual curves
slope upward;
(2) the left hand seems equally efficient, as compared with the right
hand.
For individual cases,
note (1) fatigue-spots are more numerous than for free movements,
especially for the left hand;
(2) weight reduces both mean and constant errors and to a less extent
even records.
For mean errors,
(1) visual control reduces errors;
(2) the weight tends to equalize the accuracy of the right and left
hands.
For constant errors,
(1) there is no general testimony showing shortening of lines at high
speeds;
(2) the less trained hand is more helped by the weight, especially for
non-visual work.
The evidence for right- and left-handed subjects is inconclusive, and
we cannot finally say that the more trained hand is capable of greater
accuracy.
Weight-accelerating movements:
The average of seven subjects:
The accelerating weight reduces mean and constant errors, and improves
regularity of curves, except for l.h.e.c. constant-error record. There
is some evidence that a pull causes overruling, while a retarding
weight causes underruling, but there are exceptions enough to warrant
care in finally accepting this statement. Visual control with
accelerating weight reduces error more than the weight acting alone.
For mean errors,
(1) weight reduces errors for r.h.e.o. and l.h.e.c. as compared with
free-movement records, while the other two curves are inconclusive;
(2) visual sense helps in accurate ruling;
(3) non-visual records are not reduced, as a rule, from the results of
free motion.
For constant errors,
(1) the accelerating weight tends to greater accuracy, with an
exception for the-non-visual records.
No testimony of marked importance is to be noted in comparison of
right-handed and left-handed subjects; the more trained hand shows
greater accuracy in some cases, but fails to excel in others; so the
data is inconclusive.
For individual cases we find:
(1) the acceleration records are more accurate and regular, and present
fewer lapses than the free or retardation results, suggesting greater
ease with weight assisting;
(2) visual control is prominent throughout, and evidence shows that
this sense is the greatest factor in the predominance of the more
trained hand; the non-visual records should and do show no marked
difference in the hands;
(3) a weight tends to equalize accuracy of hands;
(4) the overruling effect of weight is over-corrected in some cases for
constant error of low rates.
Constrained movements of 1 cm.:
The average is of seven subjects, three of them being left-handed:
With weight-retarding movement, there is no reduction of mean error
with visual control of right hand, but there is with the left. Constant
errors show little reduction for either hand with eyes open.
The facts would seem to warrant the hypothesis that, for the left hand,
a movement uncontrolled visually, whether restricted by a weight or
not, can be made with greater accuracy, when time is permitted for
discriminative and reflective processes and visual-control results in
about the same error whatever the speed, while the right-hand motions
show no such evening effect of visual control with the weight-records
or even reduction of error; the free movement, however, does show a
reduction of error.
A general statement may be deduced that, for lines of 10 mm. in length,
there is no difference in either mean or constant errors, when a weight
is imposed to cause retardation, provided the weight is not large
enough to cause pain or fatigue.
By separating the averages for right- and left-handed subjects, it may
be further said that:
Visual control is not efficient to reduce the error and no particular
gain in regularity can be noted. The left-handed subjects show, for the
left hand, much better results without visual control as far as the
free motion is concerned.
While somewhat contradictory, it may be stated that constant errors
are reduced by the weight addition, and there is some evidence leading
to the belief that the ruled line is shorter when the weight acts as a
retarding influence.
INDIVIDUAL RECORDS
Considering lines 10 mm. long with a retarding weight:
A glance over the seven individual records shows some considerable
increase in both constant- and mean-error irregularities, as compared
with the free-motion curves, as well as in actual errors; there are
distinct losses of volitional control for both classes of errors,
especially at or near the ends of the series.
There are cases of very low mean error to be found on all records,
where the value is 1/4 mm. or less, and, while the same phenomenon
is found with free motion, it is more marked here and occurs more
frequently; in most cases it seems as a drop from errors of larger
values rather than a gradual matter, as if the subject realized the
large error and exerted unusual volitional control to correct and
produce a very accurate record, but found that the attention needed was
beyond his will-power, as shown by the immediate lapse of accuracy.
There is an indirect confirmation of this view from the introspective
testimony of the subjects.
The visual element steadies but does not reduce mean errors when weight
is retarding.
The general shape of curve for eyes closed is downward 20-40 beats,
and rising for the rest of the series; it is less regular, but more
accurate than the visual results.
The fact that constant errors are mostly positive leads to a denial of
any inhibitory effect of the retarding weight.
For 1 cm. lines,
weight-retarding movements:
For the average of seven subjects we find:
(1) visual control does not improve accuracy or regularity as in free
movements;
(2) a retarding weight tends to make errors constant whatever the
speed-rate;
(3) the testimony goes to show that the free-movement records are more
accurate than the retardation ones.
Mean errors are:
(1) no more accurate and perhaps less regular, when the weight is
imposed;
(2) right- and left-handed subjects are equally accurate.
Constant errors:
(1) the more dexterous hand is superior for coördinations requiring
accuracy;
(2) ruled lines are slightly shortened in some cases;
(3) weight-records do not give more accurate results as compared with
free movements.
For individual records we find:
(1) retarding weights increase errors and irregularity;
(2) fatigue-points are more marked and frequent than for free movements.
Mean errors,
(1) the visual factor is of some value, but the testimony is varied;
right hand for increased regularity only, and left hand for greater
accuracy only;
(2) curves are horizontal or reducing with speed-increase.
Constant errors,
(1) the more dexterous hand coördinates better;
(2) all errors are positive;
(3) visual control helps only for regularity;
(4) curves are horizontal or rising.
With weight-accelerating movements, the average record shows a
sudden rise in mean error at both ends, not in evidence with free or
retardation results.
In general it is to be noted:
(1) that the visual element is of no value for reducing the error, and
of little value for promoting regularity;
(2) that the pull-records are closely comparable to the free-motion
records, and the accelerating influence of the weight is imperceptible;
(3) that the pull-records are more regular and closer to the
free-motion curves than are the weighted records, especially at the
ends of the left-hand curves.
For constant errors:
It is more in accord with the facts to say that the imposition of a
weight tends to reduce the constant error, and this is more marked when
the weight acts in pulling or to accelerate the motion.
Comparing with the weighted curve, we find the same general type of
rising curve, similarly located, and the same is true when compared
with the free-motion curve. Constant errors are reduced, but slightly,
and visual control is rendered nil, when the weight acts either to
accelerate or retard the movement, and of the two, the accelerating
effect is more marked, as reducing errors and promoting regularity.
There is no appreciable tendency for the weight to reduce the ruled
lines when retarding motion, nor is the weight as accelerating, able to
extend the line beyond the point set in the free motion.
When contrasting averages from right- and left-handed subjects it may
be said:
As compared with free motions there is a slight reduction of error and
irregularity more marked with the left-handed subjects, but a general
close correspondence of results.
The question is now appropriate, why should the right-handed men show a
reduced error for speed-increase, while the left-handed subjects show
the reverse? Bearing in mind that the right hand is the more dexterous
or better trained in the former case, it may be suggested that the
order of record from 20 toward 200 beats is such as to cause more
accurate results at the upper limit, in spite of the fact that less
time is allowed for discrimination and adjustments; on the other hand,
left-handed subjects have much less advantage of practice and habit in
their use of the right hand, and will show the predominance of error,
when the ruling is too rapid for careful discrimination.
It becomes a struggle between automatism, or semi-automatism, on the
one hand, and discriminative processes on the other.
Visual control is not an advantage in the case of accelerating weight,
and the large reduction in error with visual control for the free
movements is not evident with weighted motions.
For the left-handed subjects we find that the eyes-closed record shows
closer work than does the eyes-open curve; it is lower and nearer the
line of 0 error; in this respect, it shows the same effect as with
the free-motion curve, and to a less extent as for the retardation
weight-record. The accelerating record is, however, more accurate and
regular than either of the other curves.
It will be clear, then, as observed, that for constant errors, visual
control tends to reduce errors and steady records whatever the
speed-increase, as far as right-handed subjects are concerned, but this
effect is not noted for left-handed subjects using the right hand, and,
with their left hand, visual control is a disturbing element.
Further this erratic effect of visual control is less marked but clear
when the weight acts as a retarding factor, but is much more noticeable
for the free-motion record.
Individual records show few lapses of control for either errors.
The bulk of the evidence is that the weight imposition, whether acting
as a retarding or accelerating influence, is effective in rendering the
results more accurate and regular, though at least one subject exhibits
the opposite effect for the accelerating weight.
The left hand is better for J., Le., and W., but is less regular for
all subjects, save Le. and W., showing again a somewhat complex mass of
testimony, from which we may conclude that the right hand is the more
accurate member for right-handed subjects, and to a much less extent
the left hand is preferred by the left-handed subjects.
Visual control is to be noted as effective for accuracy and regularity,
except for Ha., where the curves closely intertwine, and for J., where
the eyes-closed record is much better.
Weight-accelerating movements:
For the average of seven subjects we find
visual control is of doubtful advantage, for left-handed subjects, but
shows a clearly marked reduction of error for right-handed subjects.
Mean errors are:
(1) similar in all respects to free-movement results;
(2) acceleration-curves are closer to free-movement results than are
retardation records;
(3) the more trained hand shows reducing error for speed-increase,
while the other hand shows increasing errors, because of superiority
of practice-effects over the native tendency to increase error as
speed-rate rises, for the more dexterous hand alone.
Constant errors:
(1) there is no tendency to overrule, as compared with free movements,
when weight acts to accelerate movements, for there are even cases of
lines being shortened with accelerating weights;
(2) a weight seems to negate the results of visual control, as a rule.
For individual records we find:
(1) fatigue-points, for the right hand only, are to be found in a few
cases;
(2) weight promotes regularity and accuracy;
(3) visual control is effective only for reducing variations of error;
(4) the better trained hand is the more accurate in the records, to a
slight extent;
(5) there are evidences of semi-hypnotic or dreamy states in the
non-visual series.
COMPOUND MOTIONS
Series of records were taken at 100 mm. and 10 mm. bases for the hands,
with what is called compound motion. This consisted in an additional
movement of the hand that was not ruling with the pencil, in a similar
manner, as regards the amplitude and general character of the motion,
but in an opposite direction.
For example, suppose the left hand is ruling a 100 mm. line outward,
or to the left; coincident with this movement would be a similar motion
of the right hand outward or to the right. The origin of both motions,
or the starting-ends of actual and imaginary ruled lines, was optional,
it being desired to bring out the effect of such additional motion, as
little complicated as possible with restrictions, as to its position
or extent. Actually this distance varied from about 10 mm. where both
motions were outward to 600 mm. for inward motions.
A comparison of such compound motions with single-hand records shows in
general the following:
For 10 cm. lines:
The case for mean errors may be summed up by saying:
(1) left-hand records are less accurate and regular than the right-hand
curves;
(2) visual control reduces error and irregularity in all cases, but is
more marked with the left hand;
(3) errors increase with speed-increase;
(4) compound-motion records show little increase in error or
irregularity, as compared with the simple motions.
For constant errors:
No marked peculiarities are to be noted, but in general,
(1) left-hand records are less accurate and regular;
(2) visual control reduces errors and irregularity;
(3) errors reduce with increase of speed, except for compound motion
uncontrolled visually;
(4) compound-motion errors are not much greater, nor is the
irregularity increased.
INDIVIDUAL CASES
100 mm. hand with compound motions.
A glance at the charts shows for individual records a few examples of
inhibition of voluntary control for both constant and mean errors, it
being much more marked in the case of mean errors.
These lapses of control appear for constant errors for A. with l.h.e.c.
at 160 and 180 beats, for mean errors for G. with l.h.e.c. at 200
and with r.h.e.c. at 180 beats; for Le. with l.h.e.c. at 50 and with
r.h.e.c. at 160 beats; for A. with l.h.e.c. at 200 beats; thus giving
evidence that the visual element has a steadying effect, and that the
left hand is less reliable save for Le.
There seems reason for contending that the compound motion can be
carried out, as arranged, without loss of accuracy or regularity on
the part of the ruling hand, and further that the subjects are pretty
generally apt to react to a given stimulus within certain rather narrow
limits of accuracy.
The evidence is here pretty conclusive that the right-handed subjects,
as a whole, show greater accuracy by about 25% for the more dexterous
hand; but it will be wise to consider the individual cases on this
point.
Greater regularity and accuracy for the right hand is attained by all
right-handed subjects, while the preference of Le. for the left hand is
clear but much less definite.
For individual cases:
The evidence again is fairly well marked that the more practised hand
will give a better account of itself even when visual control is not
called on.
The results for compound movements of the hand for 1 and 10 cm. lines
are summarized as follows:
It should be kept in mind that the compound records were in all cases
taken in connection with a duplicate series of lines for one hand, and
called simple movements. These simple movements correspond with the
free-movement records that have been considered already.
The purpose has been to bring out the modification of results that a
compound movement introduces, rather than to bear heavily on intrinsic
phenomena, _i. e._, comparison is deemed more important.
For lines 10 cm. long:
Average of seven subjects:
We find for mean and constant errors:
(1) left-hand records are less accurate and uniform;
(2) visual control increases accuracy and regularity, especially for
the left hand;
(3) there is an increase as the speed increases for mean errors, and a
decrease for constant errors;
(4) compound movements are practically as accurate and regular as the
simple ones for constant errors.
For individual cases:
(1) a few lapses of control or fatigue-spots more marked for mean
errors with the l.h.e.c., for the visual sense steadies ruling, and the
left hand is less reliable;
(2) compound and simple records show close agreement;
(3) the more trained hand reacts more accurately, and with greater
regularity;
(4) non-visual records show a cautionary shortening of line at low
speeds, and another at the upper limit, the latter being due to
physiological limitations.
For 1 cm. lines:
As far as averages are considered:
We may say, then, for mean errors:
(1) that visual control is effective for reducing errors, and
increasing steadiness in both sets of records, being more marked with
the less trained hand, the left;
(2) only in the case of the l.h.e.c. curves is the movement of the free
hand noted as appreciably affecting the accuracy or steadiness of the
record.
(3) eyes-closed records in general show a considerably greater error at
20 beats that practice rapidly reduces up to 40 to 60 beats.
We may note for constant errors:
(1) all errors are positive and confirm the earlier deductions on this
point;
(2) visual control reduces error and improves steadiness of record;
(3) the free hand-movement does not affect either the accuracy or
uniformity of results;
(4) errors do not increase with speed.
For individual records:
Comparing the individual cases of simple and compound movement, there
is no particular reason for concluding that the compound movement
is a disturbing influence as far as the records of all subjects are
concerned, save possibly the lapse of G. at 20 beats, and on the other
hand a case of greater accuracy and evenness for compound movements for
Mo. with r.h.e.c. constant error.
It is, then, possible to extend the conclusion of the 10 cm. records,
and say that both lengths of lines are ruled with a fairly constant
limit of error, whether the movement be simple or complicated by
movement of the free hand.
Individually there is testimony in favor of the gain in accuracy with
visual control for Hu., Hy., and Le., while the crossing of curves for
the other subjects shows that there is no difference in eyes-open and
eyes-closed results, the general conclusion being in favor of the value
of the eyes for accurate results.
For mean errors the right hand is more efficient in the case of A.,
Hu., Hy., and Me., while the reverse is the case for the rest, and the
evidence goes to suggest that greater accuracy can be attained with the
more practised hand.
For constant errors the right hand is more accurate in the case of A.,
G., Hy., only; Me. and Mo. are equally accurate with the hands, and the
rest show a marked preference for the left hand, the evidence being
thus conflicting, pointing to the theory of ambidextrous development on
the lines of accuracy.
L.h.e.c. records are horizontal for all subjects except Hu., Me., and
Mo., who show an upward slope to the curve. Evidences of visual control
as giving greater accuracy are noted in general above 70 beats and
individually for Hy. and Mo., only, the remaining records being so
intertwined that no difference can be noted, all suggesting that the
eyes are of but little assistance when the left hand is considered. The
right hand is preferred with eyes closed by A., Hu., and Le., while
four right-handed subjects testify that the less trained hand is more
accurate.
The testimony here seems conclusive as pointing to a denial of the
current notion as to the greater accuracy of the right hand for
right-handed subjects, and of the left hand for left-handed subjects,
and further suggests that visual control is a large factor in the
supposed superior excellence of the hand mentioned.
SUMMARIZING
For lines 1 cm. long:
Average of seven subjects:
It may be said that:
(1) visual control reduces both mean and constant errors, especially
for left hand;
(2) errors are constant whatever the speed;
(3) constant errors are positive showing overruling in all cases;
(4) there is no disturbance created by the second-hand movement, save
for r.h.e.c. mean errors, where the accuracy is less for the compound
records; this is probably due to the fact that this record shows the
least evidence of voluntary control, and is thus most subject to
disturbances;
(5) there is a marked reduction of mean error 20-50 beats, probably due
to practice.
For individual cases note:
(1) fatigue-spots for non-visual mean errors only;
(2) the equality of result of both types of movements is noted for all
cases;
(3) the non-visual right-hand records for some subjects are more
accurate;
(4) the more trained hand is not, as a rule and subject to exceptions,
the more accurate one, especially for the non-visual records; and
(5) there is evidence that the superior accuracy of the right hand for
right-handed subjects is largely a matter of visual control.
HEAD-RECORDS
There was no attempt made to differentiate the visual element because
the very movements of the head prevent the full use of the eyes; as a
matter of fact, the subject's attempt to make use of the eyes and the
aid is more marked at slow speeds and upon facing the apparatus. It
is to be noted here that the visual element, as reducing the error at
low speeds, is equally marked whether the eyes are directed toward the
recording pencil or not. This raises an interesting question as to the
direction the eyes must take for the optimal result; must the eyes be
fixed on the moving pencil, on its immediate surroundings, or may they
wander at will about the surrounding objects?
My own introspective testimony, corroborated by others, who have acted
as subjects for this investigation, is that the eyes are most effective
when gathering spatial relations in a gross way, and it may be expected
that the effects of visual control as reducing errors will be equally
efficient, whether the recording pencil be screened or visible,
provided it be possible to bring on the retina objects that are grouped
about the centre of attraction, the pencil, but not in its immediate
neighborhood.
The records show that there is underruling at the higher speeds because
of physiological limitations; but this shortening is greater for the
backward movements, for the position of the subject is such as to lead
to greater uncertainty as to the exact length of ruled line, and it is
probable that a cautionary or inhibitory feeling is the cause of this
shortening beyond what will be clearly due to inability to perform the
desired movement.
Further, visual control is effective, in the case of constant errors,
in lengthening the ruled lines at high speeds, and thus reducing the
negative constant error.
While the muscular control of the head is a constant, whether the
movement be forward or backward, it is less effective for constant
error reduction when the head is moved backward. Consequently, while
the backward and forward curves are fairly well in correspondence,
there is some reason for offering the proposition that either the
eyes are of assistance in forward movements to reduce mean errors at
high speeds, and they are of no such value for backward movements, or
the muscular control of the platysma myoides, trapezius and associated
muscles of the neck group is more nearly perfect for movements of the
head forward than for backward motions, the latter being to my mind the
better hypothesis.
The results for head-movements for lines 1 and 10 cm. long are
summarized:
For lines of 10 cm. length:
Average of six subjects:
For mean errors:
(1) the curve for head-forward and head-backward closely corresponds
to l.h.e.c. record; the errors increase by 50% with increase of
speed-rate, suggesting that
(_a_) visual control is negligible, as far as seeing the moving pencil
is concerned;
(_b_) control of head for forward equals that for backward movements.
For constant errors:
(1) there is underruling at high speeds because of the usual
physiological limitations, and this is more marked for head backward
results, suggesting that
(_a_) spatial relations are obtained, when the apparatus is visible,
that tend to correct underruling, or
(_b_) an extra inhibitory effect, due to lack of knowledge of spatial
relations, is added to the normal physical shortening and the subject
moves the head a less distance than is naturally possible; or
(_c_) the muscular control is less complete for movements of the head
backward.
For individual cases we find:
(1) fatigue-lapses are less in magnitude than for the hands, because
the head-movement can be only a fraction of the forearm-movement;
(2) mean errors increase and constant errors decrease with speed-rise;
(3) similarity of individual head-forward and head-backward curves is
suggestive, taken with the fact that no typical form of curve is to be
found;
(4) head-backward constant errors are greater and less regular in all
cases, suggesting that the eyes, in head-forward records, by getting
spatial relations, are more efficient.
For lines 1 cm. long:
Average of six subjects:
For mean errors note:
(1) the head-backward records are less regular than the head-forward
ones, and rise a little with speed-increase, showing visual assistance
for accuracy or better muscular control for the forward movements or
both;
(2) the constant errors show shortening of ruled lines at high speeds a
little more marked for the head-forward results;
(3) there is constant overruling.
Individual cases suggest:
(1) fatigue-spots are apparent, especially for head-backward movements;
(2) errors do not increase with speed;
(3) the movements of the head forward are under better control.
FOOT-RECORDS
10 cm. records show that
(1) the eyes are of no assistance as to increasing accuracy but help in
promoting regularity of error;
(2) a shortening of ruled lines with speed-increase is noticeable, and
is probably due to the usual physiological reason;
(3) the feet are capable of less accurate motion than the hands, but
show better results than the head;
(4) mean errors increase but constant errors decrease with
speed-increase.
Individual records show:
(1) less violent fluctuations of errors in all respects than do the
results of head or hands, for vertical foot-movements are of less
extreme extent than are arm- or head-motions;
(2) that for visual control with mean errors, no foot is the more
accurate, and there is no reason to believe that the feet are unequally
educated.
1 cm. records show, as far as mean errors are concerned, that:
(1) visual control is of no value as either reducing actual errors or
as effecting greater regularity;
(2) Errors for foot-movements are no less, but considerably more
regular than for head-motions;
(3) errors for hand-movements are more regular, and only 50% of the
results for either head- or foot-movements;
(4) all curves are horizontal;
(5) there is no appreciable advantage as to accuracy or regularity that
can be attributed to either foot. The evidence goes to show that the
subjects are ambipedalous, if it be permitted to coin such a word.
In general, we find that, as far as constant errors are concerned,
(1) visual control does not help to reduce actual errors or promote
uniformity;
(2) errors for foot-movements are less than the head records, and but
little greater than the hand results, while the regularity for the feet
is comparable to the hand, and much greater than for the head;
(3) all curves are horizontal;
(4) there is no particular advantage that either foot has over the
other either as to accuracy or regularity.
The evidence is that the subjects were ambipedalous, as far as ability
to reach a certain point equally well by either foot is concerned.
The popular notion has been to the contrary, and it is a point of
considerable importance to note the last point.
For example, in kicking, as developed by football trainers, it is
commonly assumed that the right foot for right-handed subjects should
be developed, and the opposite foot for left-handed men. Or again, in
the case of a person lost in the woods and walking in a circle, it is
observed that right-handed persons will turn to the left; probably
because of the pace of the right foot being slightly longer than the
left. My reply to this evidence will be that the data herein presented
is for vertical movements of the foot, starting from the floor in every
case, the subject being seated in a chair.
On the other hand, it is an entirely different movement, calling for a
much different and greater muscular control in the case of kicking or
walking that must be considered. For this reason the evidence, while
conclusive within its range, is not offered as more than suggesting
that the feet are equally well trained for the usual adjustments, and
only an exhaustive investigation covering all possible foot-movements
will settle the question.
The result for foot-movements for lines 1 and 10 cm. long is here
summarized.
For lines 10 cm. in length:
Average of seven subjects:
Note in general that
(1) l.f.e.c. mean error is most erratic, while the same curve is the
most accurate, as far as constant errors are concerned;
(2) the left foot mean and constant errors are slightly greater than
those for the right foot, for visual records;
(3) mean errors increase and constant errors reduce with speed-increase;
(4) the visual sense improves regularity, but does not reduce errors;
(5) there is a physiological reason for the shortening of lines at high
speeds;
(6) the feet are more under control than the head, but less than the
hands.
For individual records:
(1) fatigue-lapses, all for non-visual, are less numerous and of less
magnitude than for the hands and head, for the vertical movement of
foot is likely to be of less extent than that of head and hands for the
particular motion required here;
(2) there is no foot capable of being called more accurate than its
mate;
(3) the eyes appear to be of no value for reducing or regulating errors
for foot-movements.
For lines 1 cm. long:
Average of six subjects:
It may be said in general that
(1) the visual sense is valueless for promoting accuracy or regularity
of curve;
(2) errors of foot-movements are more regular and, for the constant
errors, more accurate than for the head-records;
(3) errors of foot-movements are less and less regular by 50% as
compared with records for the hands;
(4) errors do not increase or decrease with speed-changes;
(5) the feet are equally accurate.
For individual results:
(1) fatigue-lapses and cases of large error-increases are noted in a
number of subjects, both for visual and non-visual records;
(2) further, evidence is available as to the indifference to visual
control;
(3) no preference for either foot is to be discovered.
The results for individual choice of rhythm.
In this series of records, the metronome was dispensed with, and
the subject was permitted to react as he desired, taking the speed
preferred because of ease, pleasure, or other reason.
Records were obtained for six subjects for feet, head, and hands, both
single-hand and double-hand movements, all for lengths of line 1 and 10
cm. The charts for individual choice were plotted for a comparison of
speeds rather than for accuracy.
It was noted for the hands:
(1) that every subject reacts more rapidly with the left hand;
(2) the eyes had little effect as to changing the speed-rate;
(3) single and double hand-movements were equally rapid.
Some subjects, as A., react more rapidly for the shorter lines, though
no clearly marked evidence of this speed-increase is to be noted.
For the head, the results for both eyes opened and closed show the
impossibility of separating the optimal or preferred rate of speed on
the score of visual assistance or because of direction of head-movement.
There is a close agreement of the subject as to his best speed, and
this is independent of special conditions; for example,
A. selects 50-57 beats per minute for 1 cm. and 48-68 for 10 cm.; G.
has a preference for 61-66 and 56-71; Hu. rises to 103-125 for 10 cm.
and selects 68-82 for 1 cm.; Le. 52-55 for 1 cm. and 45-52 for 10 cm.,
and so on.
We may say, then, that free rate-choice for head-movements results in
a selection of some rate of speed that is not affected by the visual
sense or direction of movement, and is strictly individualistic,
covering a range of 50-130 beats per minute, and not increasing as the
amplitude of movement is reduced.
Turning to individual choice of speed-rate, for the feet it will be
seen that
(1) the non-visual records closely correspond as to chosen speed, and
there is a less close correspondence of visual speeds;
(2) the visual records are ruled at a lower rate in some cases, but A.,
G., and Mo. show little difference;
(3) there is a tendency to speed up as the series progresses;
(4) the shorter lines are ruled with greater speed as a rule, though G.
and Le. fail to show this phenomenon;
(5) The left-foot records show a higher speed-rate for all cases.
Among many interesting points that cannot be examined in this
connection, such as relation of voluntary choice of rate to the main
line of metronome records as regards accuracy, the fact of the higher
rate of ruling for the left hand and foot stands most prominent.
Whether a record of head-movements to right or left, or other devices
to compare the sides of the body or to contrast arm and leg speeds,
will bear out this testimony is as yet unknown, so that the writer
prefers to announce the result and not now fit theory to data. It may
be said that the records were taken in reverse order and rearranged,
as regards right and left foot or hand, and, in addition, the initial
foot-movement varied with the subject, some being right and some left.
We ask finally: Is the time in which the greatest exactitude is
produced, the same for every group of muscles; that is, has every
motor apparatus the same natural rhythm? and: Is this natural rhythm a
constant rapidity for all motor nerve-centres or does it depend upon
the complexity and character of the movement?
The comparison will fall first on the averages and finally on the
individual records.
The hand-movements show the following results:
Constant errors for 14 cm.:
For simple and weight accelerating and retarding motions, there is a
close agreement about 120 beats for the minimum error for visual and
right-hand non-visual records; left-hand non-visual records are spread
more, but will also average the same.
For 10 cm. simple and compound movements the visual minimum errors are
at 180-200 beats, while with the eyes closed the results are grouped
about 60 beats; one record, that for l.h.e.c., has two minimum points
at 60 and 180 beats, the latter being clearly a crossing of the 0
error-line, because of physiological limitations.
For 1 cm. simple and weighted minimum errors are grouped between 20 and
60 beats, while the simple and compound group show less regularity and
a tendency to group minimum errors at 100 beats.
The head-movements show for both 1 and 10 cm. lines a minimum error at
180-200 beats, there being, however, one exception at 100 beats for 10
cm. head-backward movements.
The foot-movements show minimum errors at 80 beats for the right
foot, and 180 and 100 beats for the left foot, visual and non-visual
respectively.
Bearing in mind for a moment the individual choice records, there seems
here a suggestion that the left foot is capable not merely of higher
speeds, but of minimum errors at the higher rates as compared with the
right foot.
No such differentiation of the hands can be discovered, however.
Mean errors:
For the hands:
For 14 cm. for simple and weighted results we find that the right-hand
and left-hand eyes-open minimum errors are at 180 beats, but the
non-visual left-hand minimums are at 30 beats.
For 10 cm. simple and compound records we find all minimum errors are
between 160 and 200 beats.
For 1 cm. simple and weighted results there is a scattering of minimum
errors from 20 to 200 beats, with a heavy preponderance at 200, and the
same is true for the simple-compound series.
The head-movements minimum errors are at 40 beats without exception.
The foot minimum errors are distributed from 20-30 beats for the left
foot to 160-180 for the right.
It is thus evident that each group of muscles and each motor centre has
its own optimum, and that the conditions of complexity, resistance,
etc., influence greatly the accuracy of the periodic movement impulse.
FOOTNOTE:
[Footnote 138: Woodworth: The Accuracy of Voluntary Movements,
Psychological Review Monographs, no. 13, 1899.]
THE MOTOR POWER OF COMPLEXITY
BY C. L. VAUGHAN
A. COUNTING OF SIMPLE AND COMPLEX VISUAL OBJECTS
If every sensory stimulus has a motor reaction, then a simple figure
perceived in any way ought to produce a somewhat different response
from a more complex figure similarly perceived. Of course if only one
figure of each kind is given it is difficult to measure in any way
this difference, since it is so small. But we might make it measurable
by multiplying the process. Therefore I have cut out a row of similar
figures in a strip of cardboard and on another strip another series of
a different pattern. Now if these rows are counted figure by figure
each figure has a certain motor effect which influences the speed of
counting, so that the time of counting (measured by the chronoscope)
should give some indication of the comparative motor power of the
figures in question.
In the accompanying illustration nine cards of various patterns are
shown. Cards 1, 2, and 3 are comparatively simple patterns while 4, 5,
and 6 are comparatively complex, Card 6 having the added complication
of different kinds of figures on the same card. Cards 7, 8, and 9 form
another group, Card 7 having the same letter throughout, Card 8 having
letters composing a sentence and Card 9 a series of the letters, mostly
consonants, mixed promiscuously. In order to prevent the subject from
knowing the exact number, and thus, perhaps, bring in another influence
at the end of the row, most of the different cards have different
numbers of figures, but this difference is not great and some cards
have the same number. The subject usually forgets, from one experiment
to the next, the number on each card.
At first the experiment was performed with the figures in a straight
row, instead of in the broken line which is seen in the illustration.
In counting the straight rows, the observers found it hard to keep the
place in the line. A subject would become confused and count some spot
twice or else he would omit it altogether. Furthermore this disturbance
was found to be much greater with some figures than with others, with
Card 1, for example, more than with Card 2. Therefore the device was
adopted of diversifying the line, both by placing some of the figures
above and some below the line and by making the distances from one
figure to the next, different in the different cases. And in order to
prevent the subject from associating any peculiar turn in the line
with a certain number counted, it was decided to have the arrangement
on the different cards different. But it was still necessary to have
the intervals between figures about the same in all the cards, and
therefore the row was divided into sections of six figures each and
these sections were used as units, variously arranged, in constructing
the other rows. For example the first unit of Card 3 is the same as the
second of Card 4. Sometimes this six-figure unit is turned end for end
or upside down, and thus, though the same spaces are used, the cards
appear dissimilar.
[Illustration: FIG. 1]
The subject would be seated at the table with one hand resting lightly
on the key which sets the chronoscope in motion, his eyes raised so
that the table in front of him is not seen. One of the cards would
then be put in the proper position in front of him (always the same),
and he is told that all is ready. He looks down at the card and as
soon as he begins to count the first figures in the line he presses
the chronoscope key, and when he has reached the end of the line he
releases the key. The time for the operation is then noted. The whole
series of cards is thus gone through. An extra card of which no record
is taken is used for the first few tests so that the subject may be in
the proper state when the first test to be noted down is taken. Also
the order of the series is changed from one experiment to the next,
each card taking its turn at being first and last. It was hoped in this
way to distribute among the different cards the effects of practice and
fatigue, and also to guard against any expectations on the part of the
subject as to the character of the next card.
The subject is told to count as fast as he can, with a reasonable
feeling of certainty as to his correctness, the main object being to
have a uniform principle, in counting the different series. Wrong
counts were excluded, but later on the same cards given again so as to
keep the tables even. Subjects were not allowed to count the figures
by groups, but one by one. At first a certain amount of difficulty was
found in the fact that subjects in counting would repeat the numbers
to themselves, and as they seemed to be retarded by this, especially
in those numbers whose corresponding names have 2 or 3 syllables, the
result was that we were getting the speed with which subjects could
count the numbers from 1 up to 38 or 39 and this would be practically
the same whatever the figure. But all the subjects were finally trained
merely to think the number, or at least to have as little vocal
adjustment as possible. When this was done the subject no longer felt
that it was the speed with which he could count that was being measured
but the rate at which he could take in the different figures on the
card, one at a time.
Between three and four hundred tests were made of the counting of the
figures on the nine cards, the work being divided among seven subjects,
though not in exactly equal amounts. Since the number of figures on the
different cards are different, I have found the time it takes to count
one figure by dividing the total time by the number of figures on a
card. The following table shows the average time taken by each subject
for one figure on each card, time given in thousandths of seconds.
_A.M.V._ stands for average mean variation.
_A._ _A.M.V._ _B._ _A.M.V._ _C._ _A.M.V._ _D._ _A.M.V._ _E._
1 279.69 11.47 186.87 13.22 247.62 14.89 193.08 12.38 262.77
2 270.60 12.47 180.55 11.88 249.21 18.00 190.51 11.82 257.56
3 274.43 9.87 180.89 11.57 247.59 15.51 192.07 7.87 259.96
4 286.82 12.47 190.39 12.56 255.20 16.78 200.53 10.72 267.11
5 290.29 11.89 195.41 12.36 262.27 19.73 199.89 9.27 271.06
6 293.06 12.21 185.33 11.51 275.40 18.13 199.20 7.92 264.59
7 273.32 15.54 192.23 13.73 229.26 19.30 185.60 9.83 265.56
8 279.77 13.86 185.23 12.69 246.66 18.86 193.39 9.81 277.52
9 285.09 11.97 197 04 12.28 269.96 19.95 186.30 9.05 259.72
_A.M.V._ _F._ _A.M.V._ _G._ _A.M.V._
20.20 217.00 12.32 442.63 36.51
16.03 195.00 9.50 431.00 24.39
17.41 191.50 11.03 434.83 24.28
20.31 226.40 29.11 445.71 14.58
20.86 233.50 20.46 459.17 18.92
15.00 220.80 14.92 432.17 26.87
19.20 189.20 30.31 402.13 21.34
14.93 220.70 21.79 388.77 27.48
14.27 210.34 11.71 419.57 18.22
A, B, C, D, E, F, G are the different subjects, and 1, 2, 3, 4, etc.,
refer to the cards with the different patterns. It is seen at a glance
that great differences exist between the rates with which the different
subjects count. Subject G had much fewer tests than the others, and
thus, not having as much training, his average is higher in comparison
than it would be had he had the same training.
Now if we compare the counting of the first three or relatively simple
patterns with that of the next three or comparatively complex ones, we
notice at once that the simple figures are almost invariably counted
in less time than the complex, there being only two exceptions. B
counts 6 a little faster than 1, and G counts 6 faster than 1 and 3.
Even these apparent exceptions are easily explained. As noted already,
subjects are much more apt to lose their place in counting certain
cards than others. This is especially true of Card 1 even after the
line is broken. Now Card 6 is arranged on a different plan from the
others, for it has many kinds of figures on it. This is a great help
in keeping one's proper place in the counting of the series, and since
wavering between two figures is avoided, the series is counted more
rapidly. But B is the most rapid in counting, of all the subjects, and
it is natural that any differences in the ease of keeping place should
show themselves here, since the more rapid the counting the easier it
is to lose the proper position. This cannot be said of G, who is a
slow counter, but on the other hand it may be noted that he had only
a few cases, and at first the ability to keep one's position is much
less than after considerable experience. So in Cards 6 and 1 there are
two conflicting principles, degree of complexity and tendency toward
confusion of position. Of course both these principles are present in
all the other cards, but they reach a maximum in 1 and 6, in 1 extreme
simplicity with difficulty in keeping place, in 6 extreme complexity
with ease in keeping place. Card 1, it will be seen, is with nearly all
subjects a little slower than 2 and 3, while 6 is generally faster than
4 and 5.
Therefore it would seem that the apparently small exceptions are not
real exceptions, but variations due to the presence of other factors
than mere differences in complexity of the figures used. In observing
the averages for 7, 8, and 9 we see that as a rule 7 is fastest, 8
next, and 9 the slowest. The tables are not quite so regular as for the
cards just given. B and G count 8 faster than 7, and E counts 9 faster
than 7. The most of these cards have on them 36, 37, 38, or 39 figures.
Card 8 has 43 letters. The subjects report that the last three on this
card are counted much faster. They know, as soon as they reach 40, just
how many there are, and it is hard to keep from counting the rest in
a group. Otherwise they do not feel any difference in counting Cards
8 and 9. Arranging the letters in words does not affect the speed of
counting, so far as they can see, for in counting they do not notice
the words at all.
When we average the records of all the subjects giving equal weight
to each subject, though the number of tests may be different with the
different men, we get the following table. Time given in thousandths of
seconds.
(1) 261.38
(2) 253.49
(3) 254.54
(4) 267.46
(5) 273.08
(6) 267.22
(7) 248.19
(8) 256.01
(9) 261.15
It is seen, from looking at this table, that all divergences from the
general rule have stopped. Cards 1, 2, and 3 each take less time than
any of the 4, 5, 6 group, and 7 is faster than 8 and 9. So the evidence
seems very strong that it takes longer to count complex than simple
figures. Should one object that the difference is extremely small, a
few thousandths of a second, and that thus a slight error in one test
might invalidate the result, we reply that the time which is given
is the time in which we count just one figure of the given pattern,
and that thus of course the difference between counting two different
figures must be very small. Moreover there has been a remarkable
agreement of the tests taken at different times. It is not a case of
finding 1, 2, and 3 counted faster one day and 4, 5, and 6 counted
faster the next, but 1, 2, and 3 are counted faster nearly every time.
Occasionally 1 will take longer than one of the 4, 5, 6 group. And
extremely seldom is there a case where the average of 1, 2, and 3 is
not less than that of 4, 5, and 6.
The experiment seems to have proven that it takes a longer time to
count a row of complex figures than a similar row of simple figures.
_The complex figure exercises a retarding effect upon the eye as it
sweeps along._ There is a greater amount of sensory stimulation,
consequently a greater amount of motor excitement. This motor
excitement does not act in harmony with the motor activity which impels
the eyes along, but has a somewhat antagonistic effect. The eye is
held more by the complex figure; it is a greater effort to withdraw
the gaze to look at the next figure. A certain interest, as we say,
on the psychological side tends to hold one to the figure looked at.
This interest is greater (other things being equal) the greater the
complexity of the figure. The nervous processes involved in counting,
though admittedly in very small degree, are thus inhibited by the
complexity of the figure and act more slowly.
B. REACTIONS TO SIMPLE AND COMPLEX OPTICAL IMPRESSIONS
Since the preceding experiments seem to show that reactions on optical
impressions are different according as the figures are more or less
complex, it would seem that we ought to be able to measure by graphic
methods the reactions to visual fields of varying grades of complexity
and in this way to demonstrate their different motor powers.
A Porter kymograph was used on which to register the reactions.
Resting on the top of the drum, and revolving with it, was a circular
band of white paper, upon which were pasted the different figures
to be observed. A screen was placed in front of the kymograph, thus
concealing the figures; but at their level was a little square window
in the screen, which, when the eye was placed in the proper position,
allowed the subject to see one of the figures but nothing more. A few
inches in front of this window was an eye-rest which kept the eye
properly placed. A tambour received the movement from the subject and
communicated it to a straw which made a scratch on the smoked paper
which covered the drum.
The figures used in this experiment form two series, one, composed of
geometrical figures, varying in complexity from a circle to a very
complex figure consisting of many overlapping squares, triangles, etc.,
and the other composed of colored figures varying in complexity from a
simple square of one color to a very complex mixture of various colors.
The area of the visual field is about the same in all cases,--an
inch square. The geometrical figures were formed of black lines on
a white background. The figures used are shown in the accompanying
illustrations.
The subject would be seated in front of the screen, his eye at the
eye-rest a few inches in front of the window in the screen, and the
forefinger of the right hand on the tambour, which is to the right of
and behind the screen, and thus not seen while the eye is at the rest.
Then as the drum revolves and brings a figure in front of the window,
the subject observes this figure carefully, and when it is all in the
field of vision he presses down with his forefinger, thus producing a
curve on the drum surface. _He tries to make the same finger-movement
every time_, whatever the figure at the window may be. But his
attention is not to be too much taken up with the making of the
movement, for he must be closely observing the figure. If he looks at
the figure until he observes its characteristics clearly and then turns
his attention from this to the finger-movement, it is evident that the
optical sensation would not have much effect upon the movement. The
movement must be performed while his interest in the figure is highest.
Now, after a little practice, any one can accustom himself to make a
certain definite movement in about the same way every time, and he can
then agree that he shall make this movement as a reaction to a given
stimulation. Then when the stimulus comes he makes the movement without
any longer thinking of the character of the movement. It has become, to
a certain extent, automatic and can look out for itself.
This is the state into which I have tried to get my subjects. Their
whole attention is to be taken up with the seeing of the figures in
the window, and to these figures they are to react as automatically as
possible. Thus, though finger-movements are usually voluntary, all the
capricious character of voluntary action will be removed here, and if
the stimulus is the same in all cases, the reaction tends to assume
the form of a uniform movement. There is, then, a chance to see the
influence of different optical stimuli upon this action.
[Illustration: FIG. 2]
Six different geometrical figures were seen at each revolution of the
drum and six reactions given by the subject. Between figures a white
surface would occupy the field of vision. The simple and complex
figures were distributed so that the subject never knew what kind of a
figure would come next. The purpose of the experiment was kept as much
as possible from the knowledge of the subjects; but some, knowing my
general problem, surmised quite correctly my main object here.
Ten revolutions were made at each sitting, thus causing the subject to
react ten times to each figure. Then a new drum paper was taken and the
case with the colored figures placed upon it. This had five colored
figures, and ten revolutions were made also in this case. Thus, in all,
in any one day, the subject would make one hundred and ten of these
finger-movements.
Since we have in all these experiments tried to find out in the
different figures merely differences in the _amount_ of the reaction,
and not differences in the character of the reaction, we shall keep up
this method here. Now a stronger reaction makes a higher curve, and
since the drum is all the while revolving, and since the higher the
curve, other things being equal, the longer it takes, the stronger
reaction will also make a wider curve. So it would seem that if we wish
to observe the differences in the amounts of reaction the most natural
course to pursue would be to measure the heights and widths of the
curves we have registered. This accordingly has been done.
In our discussion of these measurements let us, then, first, take up
the curve heights, and of these, those of the geometrical figures
which we call _U_, _V_, _W_, _X_, _Y_, _Z_. The height is measured
from a base-line [drawn by revolving the drum after the subject has
taken his finger from the tambour] to the highest point reached. These
measurements are taken from two hundred reactions to each figure,
divided among seven different subjects.
_Heights of Curves_
_U_ _V_ _W_ _X_ _Y_ _Z_
_Subject_ A 6.83 6.68 6.59 6.55 6.63 6.79
B 8.64 7.26 6.41 7.79 6.39 9.75
C 6.67 6.55 6.73 6.85 5.87 8.53
D 21.35 21.26 21.46 21.90 21.33 21.31
E 16.13 15.77 15.17 15.85 15.29 16.08
F 16.90 16.97 16.14 16.52 15.81 17.91
G 11.42 11.32 11.39 11.48 11.06 11.10
87.94 85.51 83.89 86.94 82.38 91.48
_Average_ 12.56 12.26 11.98 12.42 11.77 13.07
_Arranged in order of height of curve_
_Z_ _U_ _X_ _V_ _W_ _Y_
13.07 12.56 12.42 12.26 11.98 11.77
If we put the figures in the order of strongest reaction for the
different subjects we get the following table:
_Subject_ A _U_ _Z_ _V_ _Y_ _W_ _X_
B _Z_ _U_ _X_ _V_ _W_ _Y_
C _Z_ _X_ _W_ _U_ _V_ _Y_
D _X_ _W_ _U_ _Y_ _Z_ _V_
E _U_ _Z_ _X_ _V_ _Y_ _W_
F _Z_ _V_ _U_ _X_ _W_ _Y_
G _X_ _U_ _W_ _V_ _Z_ _Y_
It is seen from these results that, although the subjects differ, the
height of the curve varies directly with the complexity of the figure.
The order of the figures, which we get by measuring the height of the
curves and then putting that figure with the highest curve first, with
the next highest second, and so on, is exactly the same order in which
we should put them if we were asked to put the most complex first,
the next second, and so on. Though the individual subjects may vary
somewhat from this rule, when they are all grouped together there are
no exceptions.
The variations of the reactions with the different subjects may be
shown very clearly in the following way, where the different figures
are in the left-hand side arranged in order of descending complexity.
"1st place," etc., refer to the order of arrangement of the figures
by the different subjects as shown in preceding tables. Thus, _Z_,
3 times, 1st place, means that three subjects have in the average a
higher curve for _Z_ than for any other figure.
1_st place_ 2_d place_ 3_d place_ 4_th place_ 5_th place_ 6_th place_
_Z_ 3 times 2 times 0 times 0 times 2 times 0 times
_U_ 2 times 2 times 2 times 1 time 0 times 0 times
_X_ 2 times 1 time 2 times 1 time 0 times 1 time
_V_ 0 times 1 time 1 time 3 times 1 time 1 time
_W_ 0 times 1 time 2 times 0 times 3 times 1 time
_Y_ 0 times 0 times 0 times 2 times 1 time 4 times
One can see at a glance from this, how, as the figures decrease in
complexity, they take their position further on in the series. If a
diagonal is drawn from the upper left-hand corner to the lower right,
it will pass through or near the larger numbers in the table, thus
showing that the figures belong in the ordered series in the places
already shown.
Next in order let us take up the measurements of the widths of curves
for the same geometrical figures which we have been considering.
_Widths of Curves in mm._
_U_ _V_ _W_ _X_ _Y_ _Z_
_Subject_ A 20.83 20.59 20.93 21.22 20.21 21.89
B 11.18 10.77 10.46 10.31 9.92 10.79
C 4.28 4.43 4.10 3.78 4.95 4.70
D 21.08 19.36 18.33 18.75 18.17 21.09
E 14.22 13.85 13.40 13.56 11.96 14.13
F 17.00 15.26 15.92 16.52 14.52 16.47
G 5.25 5.19 5.30 5.08 5.11 5.37
93.84 89.45 88.44 89.22 84.84 94.44
_Average_ 13.40 12.78 12.63 12.75 12.12 13.49
_Order_ _Z_ _U_ _V_ _X_ _W_ _Y_
13.49 13.40 12.78 12.75 12.63 12.12
If as before we take the orders for the different subjects, we get the
following table:
_Subject_ A _Z_ _X_ _W_ _U_ _V_ _Y_
B _U_ _Z_ _V_ _W_ _X_ _Y_
C _Y_ _Z_ _V_ _U_ _W_ _X_
D _Z_ _U_ _V_ _X_ _W_ _Y_
E _U_ _Z_ _V_ _X_ _W_ _Y_
F _U_ _X_ _Z_ _W_ _V_ _Y_
G _Z_ _W_ _U_ _V_ _Y_ _X_