238 
IOWA ACADEMY OF SCIENCE Voi,. XXVII, 1920 
of the best observers tends to become a straight line and that 
of the others tends to remain broken. 
As a check on the value of the measure, ten men from the 
Engineering shops were measured. Each man was given twenty- 
five trials and the results compared with the rating on mechanical 
ability given by their instructors. In six cases the two ratings were 
near enough to be significant, but the other four showed consid- 
erable discrepancy. The one case where the difference was most 
marked was rated by the instructors as being mentally unable 
to make good in a machine shop. As this measure is not a 
measure of mental ability the discrepancy is not as alarming as it 
at first appears. 
On the whole, while the results of this investigation are some- 
what negative, they are still sufficiently encouraging to continue 
the work, which is as yet scarcely well started, until a measure 
of a person’s ability to acquire skill in the coordination of eye and 
hand is eventually evolved. 
A STANDARDIZED MEASURE OF MOTILITY 
MERRILL J. REAM 
In any survey of the fundamental capacities of motor control 
the factor of speed of simple movement is obvious as one of the 
basic essentials which underlie all the developed complexities 
of movement. This fundamental capacity for speed in a simple 
repeated movement we call motility, and the motion selected is 
an easy movement of the forearm in which the finger taps a tele- 
graph key. This type of movement is selected because it is one 
of the most rapid of the voluntary movements; it is clearly de- 
veloped, is very simple, and requires no learning. It is assumed 
that the ability shown in this movement is, in general, indicative 
of corresponding ability in other parts of the body. 
The investigation of motility has resulted thus far in a stand- 
ardized apparatus and method for conducting the test. It was dis- 
covered that for most people voluntary movement can not be 
maintained at its maximum rate for more than five seconds. To 
measure accurately and easily this short interval of time, an ap- 
paratus was devised which eliminates the reaction time of the 
experimenter and the observer. The apparatus, in addition to the 
telegraph key, consists of a metronome, a specially reliable electric 
counter, and a double action shunt key. The metronome is ac- 
