Relation of Age and Mongolism to Lateral Preferences in Severely Subnormal Subjects

Abstract

HILDRETH¹ estimated the incidence of left-handedness in very young children to be about twice as high as in the adult population. This is consistent both with an effect of social training and also with maturation in lateral dominance, but in either case one might expect a subnormal population to show, at least up to a certain age, a greater incidence of left-handedness. Burt² and Gordon³, relying partly on the observations of teachers, both found this; Clausen⁴, however, using three objective tests, found no differences between retardate and normal groups aged 8 to 10 years. Severe subnormality, however, has scarcely been investigated; the children examined by Burt and Gordon, and the 46 per cent of Clausen's retardate subjects with IQs above 60, would almost certainly not be so graded. An attempt⁵ to differentiate by diagnosis ranked the incidence of left-handedness in groups of subnormal males in the (diminishing) order: “familial”, “brain-damaged”, “mongols”. It therefore seemed worthwhile to investigate lateral preferences in normal and severely subnormal groups, examining separately the effects of age and mongolism.