TRANSACTIONS OF SECTION L. 



627 



defective. Many are to all outward appearances so different from normal 

 children. Some of the lowest-grade defectives possess remarkable cunning, which 

 is often mistaken for intelligence. 



It is important to determine what is the essential nature of mental deficiency. 



The method of mental tests has been introduced for measuring mental ability, 

 and also for ascertaining whether there is a central factor (i.e., a general ability) 

 common to all mental processes. 



It is essential for us to assure ourselves that all the experimental re- 

 sults obtained furnish information of a reliable character about the abilities 

 measured. 1 



My investigation, which lasted nearly three years, was carried out on those 

 children who are usually spoken of as the ' backward ' type. The tests were 

 carried out under the best conditions possible. The children were examined 

 singly, and disturbance of any kind was carefully avoided. They were 

 encouraged as much as possible to do their best. In order to show evidence of 

 the existence of a ' general ability ' common to all mental processes, it was 

 decided to measure as many abilities as could be conveniently arranged. The 

 results of these tests then showed whether there was anything in common 

 between the different processes. 



The following tests were employed in this investigation : — ■ 



1 Tapping. 



2. Crossing out rings. 



3. Crossing out sets of dots. 



4. Immediate memory for sentences. 



5. Immediate memory for names. 



6. Immediate memory for commis- 

 sions. 



7. Discrimination of length. 



8. Interpretation of pictures. 



9. Geometrical figures. 



The head-teacher at each school was asked to draw up a list of the children 

 to be examined in order of their 'practical intelligence.' She was also asked to 

 give two further lists of the same children in order of their scholastic attainments 

 — one for reading and the other for arithmetical ability. The results obtained 

 from each of the tests gave a moderately high correlation with the teacher's 

 estimate of ' practical intelligence,' but when all the tests were pooled together 

 the correlation was quite high. On the other hand, neither reading nor arith- 

 metical ability correlated very appreciably with the tests. This clearly shows 

 that Binet is not altogether justified in considering scholastic attainment as the 

 supreme criterion of 'general ability.' It also indicates that the earliest investi- 

 gators were unwarranted in claiming that the tests are adequate for classifying 

 children for scholastic purposes. 



The investigation has shown that there is quite an appreciable intercorrelation 

 between the tests, especially in the case of the girls. All evidence goes towards 

 corroborating the popular conception that there is a central factor — a general 

 ability — common to all mental processes. 



By pooling together the results of all the tests we obtain the ' global ' or 

 ' amalgamated ' result. By this means the specific factors in each of the tests are 

 more or less eliminated, and the ' global ' result should give us a very fair idea 

 of the subject's ' general ability.' 



There is every reason to believe that the central factor is not conative but 

 rather intellectual in character. In the case of defectives it is not so much the 

 willing process itself that is at fault as the ability to execute what is willed. 



These defective children continue to develop appreciably up to quite a late 

 age, whereas development in the case of normal children ceases to be marked at a 

 much earlier stage in life. 



The prevailing methods for examining mental deficiency are far too inade- 

 quate. The present custom of determining after a brief interview lasting two or 

 three minutes the mental condition of a child can only excite grave misgivings. 



In conclusion I would like to urge the necessity for the ' intermediate ' school 

 between the normal school and the school fov mentally defectives. Some of the 

 tests employed in this investigation could prove very useful for arranging the 

 children for this purpose. There is no doubt that such an arrangement would 

 render our educational system much more effective. 



1 Dr. Spearman's method of Correlational Coefficients has been used by me 

 throughout this investigation for measuring correlations and reliability. 



6 s s 2 



