116 PSYCHOLOGY: R. M. YERKES 
1st trial 2nd trial Credit 
(a) 374 581 (1) 
(b) 2947 6135 (1) 
(c) 35871 92736 (1) 
(d) 491572 516283 (1) 
(e) 2749385 6195847 (1) 
The preliminary scale, which we have thoroughly tested by applying 
it to about eight hundred normal children and adults and to more than 
three hundred abnormal individuals, has proved so serviceable that we 
are now attempting to develop a more highly perfected and inclusive 
series of measurements which shall be universally applicable and shall 
take account of the affective as well as the intellectual functions. 
Since the object of our work was the development of a practically 
serviceable method of measuring mental ability for use in hospitals, 
clinics, schools, reformatories, prisons, and wherever a rough estimate 
of mental status is demanded, it does not seem worth while to present 
results in this article. 
The principles involved in the universal point scale are as follows: 
1. A single series of measurements to be made on all subjects examined. 
2. Gradation of each member or part of the scale with respect to 
difficulty so that measurement may be made, with equal facihty, of 
the capacity of the child of three and the adult. 
3. Partial credits according to the extent apd nature of the response. 
4. Distribution of the several measurements equally among the chief 
groups of mental processes: for example, according to the following four 
categories of processes, one-fourth of the measurements being devoted 
to the processes under each, {a) Sensibility, perceptivity, discrimina- 
tion, association (receptivity) ; (6) Memory, in several of its aspects, and 
imagination (imagination); {c) Simple feeling, emotion, sentiment, voli- 
tion, and suggestibihty (affectivity) ; {d) Ideation, judgment, reasoning 
(thought). 
5. Arrangement of the several measurements of the scale, probably 
twenty in all, in the four groups suggested above, namely, {a) recep- 
tivity; (6) imagination; (c) affectivity; (c^) thought. So that, one-fourth 
of the scale being devoted to each group of processes, the credits achieved 
by an individual may conveniently be represented by a simple formula. 
Assuming that the maximum number of credits obtainable is two hun- 
dred and that individual X achieves one hundred and fifty- three points, 
his mental formula might be written thus: 
X = R.43 -f- 1.48 -t- A.22 + T.40 = 153. 
