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38
Percentage distribution of education abilities.
Subject.
M.D. Act
cases.
Special
school cases.
Subject.
M.D. Act
cases.
Special
school cases.
Reading—
Writing—
Nil
30.3
13.2
Nil or scribble
37.7
2.1
Some letters
13.3
14.4
Strokes and some letters
16.1
19.5
Most letters
15.1
16.6
Easy words
21.8
57.6
Some two-letter words
16.1
17.1
Write well
24.3
20.8
Some three-letter words
5.8
13.9
Infants' primer
4.6
12.4
Calculation—
Standard I.
6.7
9.7
Unable to count to 4
49.2
9.8
Standard II.
4.9
2.0
Count to 4 but not 13
8.6
23.2
Better
3.2
.5
Simple addition
27.6
57.1
Better
14.5
9.9
The classification according to the degree of defect under the Mental Deficiency Act has, of
necessity, owing to the statutory definition, been based chiefly on the information as to conduct.
With a view to checking how far these decisions are in accordance with estimates based on mental
age alone, the average mental age and chronological age have been ascertained for each of the classes.
Class. Number examined. Mental age.Chronological age.
Feebleminded 980 8.1 19.2
Imbecile 1,191 3.8 11.1
Idiot 232 1.7 9.6
American observers have usually deemed idiots those whose mental age was 2 or less, imbeciles
those whose mental age was 7 and under, and moron (which is equivalent to feeble-minded) those from
8 to 12 or 13. The figures in the third column above show that the cases classed as imbecile during the
last six years must have contained a certain number who would have been deemed idiot on the American
scale, and the feeble-minded class a certain number who would have been deemed imbecile.
Details have been taken out separately for each of the chief clinical types to ascertain how far
the nature of the defect influenced the mentality and mental age quotient. It is clear that a further
analysis will be required before definite opinions can be expressed, though the lower grade of the mongol
and of those with double defects is evident.
Male. Female.
Nature of the defect. No. examined. Mental age. Chronological age. Quotient. No. examined. Mental age. Chronological age. Quotient.
Primary amentia 672 5.8 14.7 .39 771 6.7 16.8 .40
Mongol 79 3.0 10.1 .30 72 3.0 9.3 .32
Cretin 21 4.4 11.5 .38 28 4.1 11.6 .35
Microcephaly 20 3.3 9.8 .34 35 3.3 10.8 .31
Hydrocephaly 27 4.1 13.3 .31 9 4.8 11.3 .42
Epilepsy 178 4.3 12.2 .35 159 4.7 12.9 .36
Paralysis 64 4.1 11.2 .36 72 3.4 10.4 .33
Paralysis and epilepsy 54 3.3 10.6 .31 57 3.2 12.3 .26
Various secondary amentias 48 4.6 11.7 .39 34 4.9 15.0 .23
Considerable interest attaches to questions of the relative fertility of defectives and also to the
influence of the order in the family. It has frequently been asserted that the influence of defect falls
most heavily on the first and last members of the family. This alleged handicap of the first-born is
but little borne out, though there was definite evidence of the incidence of certain types of defect on the
later members of the family, particularly mongolism and other varieties of infantilism. Although the
average size of the family appears to be greater in the case of defectives than of normal stock, the result
would appear to be largely neutralised by the differential death rate.
Nature of defect.
No.
observed.
Order in
sibship.
Size of
fraternity.
No. dead.
No. of
survivors.
Primary amentia 1,285 4.1 6.5 2.2 4.3
Mongol 140 6.1 6.7 1.7 5.0
Cretin 44 4.2 6.5 1.4 5.1
Microcephaly 42 3.8 5.4 1.6 3.8
Hydrocephaly 29 3.4 6.4 2.7 3.7
Epilepsy308 4.2 6.4 1.9 4.5
Paralysis 129 4.0 5.6 1.6 4.0
Paralysis and epilepsy 110 3.4 5.3 1.6 3.7
Various 75 3.4 5.5 1.6 4.0
Defectives in M.D. schools 1,000 4.3 6.3 1.9 4.4
Scholarship candidates 1,000 2.9 4.8 .5 4.3
This table will be read as showing that the average case of primary amentia was the fourth in a
family of 6-5, of whom a little over four were still living at the time of enquiry. The more severe the
nature of the defect, the smaller the number of survivors.