Per Cent of cases showing improvement
Period 1 Period 2 Period 3
Based on 31 cases 32·2
Based on 18 cases 33·3 66·6
Based on 11 cases 36·3 63·5 100
Based on all groups 33·9 65·0 100

These cases were compared with a control group chosen at random. They comprised a total of 100 children who had records for four consecutive school years.

TABLE B

Table showing how time of improvement of "operated cases" compares with improvement among children at random.

Period 1 Period 2 Period 3
A—Per cent of 31 cases (operated upon) 32·2
Per cent of 100 children at random 42
B—Per cent of 18 children— 20 months (operated upon) 33·3 66·6
Per cent of 100 children at random 42 41
C—Per cent of 11 cases for 30 months (operated upon) 36·3 63·5 100
Per cent of 100 children at random 42 41 41

"... Immediately after operation, there seems to be a dropping off in the quality of school work done," but thereafter a marked improvement while the random group shows a comparatively static percentage of improvement from year to year. The conclusion of the author is:

"Here seems good reason to believe that the removal of diseased tonsils and adenoids is a factor in beneficially influencing the mental life of the school child. Not only is the health impaired by failure to remove these diseased parts but the mental life and activity of the child as well."

It is conceivable that pedagogical retardation might exist without any defect of intelligence. The physical effects of adenoids and tonsils might produce a tendency to fatigue, an emotional instability and consequent lack in attention, which would seriously influence the quality of school work, even though the child were of normal or superior intelligence. The relation of physical defects to intelligence has been investigated experimentally by a method which will be employed to some extent in the present investigation. In the two studies to which I refer psychological tests, rather than school standings were used as a basis for judging the intelligence. In each the effects of treatment were measured, and in one, a control group makes possible a more accurate interpretation of results.

The first of these investigations is described by Wallin.[13] It was "an attempt to determine by controlled, objective, mental measures the influence of hygiene and operative dental treatment upon the intellectual efficiency and working capacity of a squad of twenty-seven public school children in Marion School, Cleveland, Ohio (ten boys and seventeen girls), all of whom were handicapped to a considerable degree with diseased dentures or gums, and an insanitary oral cavity." The experiment extended over one year, from May, 1910, to May, 1911. The treatment included corrective work upon the teeth and mouth, and also instruction in oral hygiene, and follow-up work by an employed nurse. Five series of psychological tests were given at stated intervals during the course of the experiment. They included tests of immediate recall, spontaneous and controlled association (opposites), adding, and attention-perception (cancellation). There were six sets of each test, numbered from one to six, of equal difficulty, and given under uniform conditions. Tests 1 and 2 were given before the treatment began, and the average was taken as the "initial efficiency." The last four, or the last two, were averaged to represent the pupils' "terminal efficiency."

The results show the following influence of dental treatment upon the working efficiency of the pupils.