SECTIONAL TRANSACTIONS.—J. A473 
of asingle dominant, a single recessive, or multiple recessive hereditary factors. There 
is such variety in diagnosis and in interpretation that it is impossible to know whether 
or not mental defect, as defined, can be the expression of different genetic forces. 
___ In the absence of accuracy in diagnosis there can be no accuracy in the interpretation 
of the genetic basis of the character. But that there is a genetic background of mental 
defect is certain. 
Mental defect, whatever may be its exact genetic nature, is a character in the 
| genetic sense. In any programme of control through breeding, therefore, genetic 
__ fact and theory are to be considered. It can be eradicated by breeding only by denying 
parentage to all those who carry the hereditary ingredients of the character, but the 
_ success of any attempt to control the spread of these among a population will be 
. determined largely by the nature and the number of the genetic factors involved. 
Dr. R. G. Gorpon and Dr. R. M. Norman.—Some Psychological Expert- 
ments on Different Types of Mental Defectives. 
Certain experiments were carried out to discover the distribution and nature of 
various functions in the mental defective. Two series were used, 100 adult girls with 
an I.Q. of over 40 per cent., and 100 boys of the idiot and imbecile class. 
(1) Head’s Aphasic tests, which were devised to test the reactions of persons with 
damage to the cerebral cortex, were applied to discover the reactions of those possessed 
of imperfectly developed cortex. The tests resolve themselves into two groups, 
those concerned with verbal and language manipulation and those concerned with 
spatial discrimination and manipulation. The former group proved very much 
easier for the defective than the latter. 
(2) Rorschach’s blot tests were applied to the same two series to test the nature 
of visual imagery, observation of colour and tendency to descriptiveness. Imagery 
could be divided into rich, fair and poor, but in all cases was restricted in scope and 
confined to concrete objects within the limited experience of the defective. Colour 
was noticed by a minority of the subjects, and descriptiveness was characteristic of 
the responses of the higher grade rather than of the lower grade subjects. - 
(3) Thorndike’s puzzle box test was applied to the same two series to discover 
the possibility of grasping a spatial and mechanical problem as a,whole, of learning 
by experience and of applying the solution of simpler puzzles to help in the solution 
of more complex problems. The last two capacities were markedly present in both 
groups, so much so in the higher grade subjects as to make the serial tests valueless. 
These were presented with the most complex puzzle only, and showed variable 
_ capacity in grasping it and solving it. The lower grade subjects were presented with 
_ the series and showed a varying ability to solve the more complex puzzles in the 
_ light of the simpler ones. 
(4) Yerkes’ discrimination tests were modified to test the power of retaining the 
image of a spatial configuration. For various reasons this was found to be useless 
as a test for the higher grade cases. In the lower grade cases interesting results were 
obtained, but only indicate so far how this method might be usefully applied in a 
more elaborate research. “All these experiments show a general but by no means 
exact correlation with intelligence as measured by the Binet and Porteus tests. 
Dr. F. C. Surussatt.—Classification of the Mentally Defective and the 
Relative Frequency of Different Types. 
It is of interest to compare the frequency of types found in the course of a statutory 
ascertainment with those found by Dr. KE. O. Lewis in his special investigation. 
Statutorily, Mental Deficiency Committees have only a duty to ascertain those who 
in addition to being defective are also subject to be dealt with, which means roughly 
that either the parents have applied for help or the persons are neglected, criminal 
or inebriate. Local education authorities have, however, a duty to ascertain all 
defective children in their area between the ages of 7 and 16, so that their findings 
‘should give a cross-section of the community. Whereas the Mental Deficiency Act 
requires the subjects to be grouped in four classes—idiots, imbeciles, feeble-minded 
persons and morally defective persons, the latter being an almost negligible number— 
the Education Act only requires a classification into those who are educable in special 
schools and those who are not, the latter being the idiots and imbeciles. 
