Memoranda presented to the Royal Commission.

  • Great Britain. Royal Commission on Population.
Date:
1950
Catalogue details

Licence: Public Domain Mark

Credit: Memoranda presented to the Royal Commission. Source: Wellcome Collection.

    52/128 (page 46)
    above. Differences in fertility between persons of the same social class but of different intelligence are considerably more important than differences in fertility between persons of the same intelligence but of different social class. May, 1945. (6) POSTSCRIPT This comment dealt with one point, the indirect estimate of the amount of the decline in test intelligence on the basis of the negative association between intelligence and family size. In particular, ] was anxious to show that Cattell’s results and those of the Bath survey were actually in close agreement. Reviewing the evidence after the lapse of four years and especially in the light of the results of the recent Scottish Survey (Scottish Council for Research in Education, “ The Trend of Scottish Intelligence ’’, 1949) some modification, not of the estimate, but in emphasis, is necessary. The repetition of the Scottish Survey shows a rise of mean group test score during 15 years and no change in terms of Binet I.Q. I still think that the estimate is valid, but the anticipated fall has been cancelled by other factors. It was stressed in the penultimate paragraph of the comment that in making the estimate no assumption was involved as to whether differences in intelligence were hereditary or environmental, and it may be that a substantial part of the association with fertility 1s conerned with the non-genetic components of variation. It may also be that changes in methods of education have made the tests slightly easier for the new generation of children. On either hypothesis the negative association between intelligence and fertility has not caused a fall, but has prevented a rise. On the second hypothesis a true fall has been masked, but on the first hypothesis a part of the anticipated fall could be truly cancelled by social and educational improvements. A third possibility is that some kind of compensatory mechanism has evolved, which tends to keep the population in equilibrium. Finally, an overlapping of generations, such as exists in the parents of 1l-year old children, combined with a falling-off of the association between intelligence and fertility, might lower considerably the actual amount of the estimated decline. In the light of the Scottish Survey, fears of an immediate catastrophic fall in intelligence as measured, due to differential fertility, may be set aside. But it is clear that important problems remain, and it is highly desirable that they should be intensively studied. September, 1949. 5. MEMORANDUM BY DR. E. O. LEWIS The evidence summarised in this Memorandum is based chiefly upon the findings of an investigation which I, with the, assistance of several colleagues, made on behalf of the Departmental Committee appointed by the Board of Education and the Board of Control in 1925. The investigation took four years ; the Committee published its report(') in 1929. This investigation was undertaken primarily to ascertain the incidence of mental deficiency in England and Wales. ‘What little evidence I am able to place before the Royal Commission relates to the qualitative rather than the quantitative aspect of the problem of population. Since the trend in this country, as in many others, during the last half-century has been towards a smaller population it is important to ascertain what concomitant changes, if any, are taking place in the mental endowments of the population. (‘) Report of the Mental Deficiency Committee (1929), H.M.S.O.