RECENT PSYCHOEOGICAE RESEARCH 
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curately timed to beat seconds and is equipped with a mercury 
contact during alternate seconds of its oscillation. The recording 
of the tapping is started and ended by the beating metronome. 
During the intervening seconds of the five seconds’ interval, a 
short circuit through the shunt key makes the recording con- 
tinuous. By this method we have an accurate recording and 
timing instrument which is also compact, portable, and usable out- 
side of the laboratory. Any graphic method of recording the 
twenty trials, which are the standardized number of a single test, 
would be exceedingly laborious. 
The efforts at standardization have shown that the fastest 
tapping is done under the following conditions : a natural forearm 
movement, the arm unsupported, a finger position in which the 
key is lightly held and a charge to the subject which stimulates 
him to his best effort. 
Most interesting have been the results of a twenty day practice 
experiment of six normal adults. There is essentially no im- 
provement with practice unless the observer was hampered in his 
initial performances by difficulties of technique. For this reason 
two preliminary practice trials are given. Non-improvability is 
very significant since it indicates that a fundamental motor capac- 
ity is being measured. 
There are individual differences in regularity of performance 
as well as in speed. The four combinations of speed and regular- 
ity are found, though more often the fast tapper is likely to be 
regular. A very high irregularity often means that there are 
difficulties of technique which a little practice or cautioning from 
the experimenter may overcome. 
The testing of children from each grade of an elementary school 
showed that motility develops consistently with age and physical 
growth until the adult physique is attained. At each age the boys 
averaged slightly better than the girls. 
Motility has a low positive correlation with other motor tests, 
but thus far no relation has been found with mental ability. Its 
future application will be in those lines of activity where speed of 
movement is an essential specification. 
