89 
1911-12.] A Method of Measuring Mental Processes. 
After the tenth minute the output rose progressively for two minutes, 
then fell for one, once more rose and finally fell. 
The curve of the excited group (Curve Z) differed totally from the 
others. Its characteristic was the abruptness of the spurts. One strikingly 
curious feature was that the excitement of beginning the task, the initial 
spurt, was practically non-existent. In the first minute the average 
amount of work throughout the whole test was almost exactly reproduced. 
This initial output was followed immediately by the greatest lapse, and 
an equally sudden recovery. The remainder of the curve consisted of a 
series of jerks, corresponding to violent spurts and lapses, the essential 
character of which was their brief duration. Their rhythmic occurrence 
was noteworthy. Their distribution clearly showed that in this phase 
of insanity the causes governing conscious effort are largely independent 
Curve Z. — Average Curve of the ‘‘Excited” Cases. 
Showing percentage variation from minute to minute from the average rate 
of the test. 
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of the task, its period, and its external accompaniments. There was no 
definite period of maximum capacity ; the two main spurts reached 
approximately the same level. The curve seems to me wonderfully to 
portray the incessant and abrupt transitions of mental energy in a morbidly 
excited brain. 
In none of these last four curves was there a terminal spurt. In the 
quiescent group the fifteenth minute was more productive than the 
fourteenth, but in it the increase was insignificant. 
In none did the Hylan middle five-minute period adequately represent 
the maximum working capacity. 
Let us now compare these curves of the mental work in morbid states 
with the curve obtained from the seven normal persons (Curve 1). Two 
striking differences are obvious in the work curve of the maniac depressive 
cases. First, a tendency towards a high output characterising the third 
five-minute interval ; and, second, the small extent of the terminal spurt. 
