RECENT PSYCHOEOGICAE RESEARCH 
2.33 
C. Timbre — its primary mechanism of control 
1. Physiological 
a. Resonating cavities 
b. Vocal cords 
c. Supra-laryngeal muscles 
d. Earyngeal muscles 
2. Psycho-physical 
a. Pitch discrimination 
b. Intensity discrimination 
c. Timbre discrimination 
D. Volume — ’its mechanism of control 
1. Physiological 
a. The general mechanism of voice production 
2. Psycho-physical 
a. Intensity discrimination 
b. Timbre discrimination 
c. Extensity discrimination 
E. Time — its mechanism of control 
1. Physiological 
a. The muscular mechanism of voice production 
2. Psycho-physical 
a. Time discrimination 
THE PERSONAL EQUATION IN MOTOR ABILITY 
MARTIN E. REYMERT 
In order to try out experimentally the common notion, that an 
individual will show a constant behaviour as to speed and ac- 
curacy in all kinds of motor performance — within his group — 
a series of reaction and motor tests were given to sophomores. 
The tests were: (1) Tapping in group (with pencil). (2) In- 
dividual tapping (on telegraph key). (3) Counting numbers 
orally. (4) Writing numbers. (5) Counting and writing as one 
combined activity. Simple bodily reactions of (6) the lips, (7) 
the jaws, (8) the index finger, (9) the head, (10) the elbow, (11) 
the thumb, (12) the foot. (13) Ergograph test. 
Throughout this test series the individual behaviour was judged 
in terms of speed (time) and variability (mean variation). The 
raw-correlations (Spearman) have been pooled. 
The main results : 
1. There is a distinct personal equation as to speed throughout 
all tests — the intercorrelations here being positive, very high and 
very reliable (as judged by P. E.). 
This result may have the bearing on motor tests for vocational 
selection, that one or two representative motor tests will suffice 
