The phrase ‘the mentality of the native’ is much on the lips of those whose work brings them into contact with Africans. The need for the study of African mentality is widely recognized; and an immense body of knowledge has accrued from the labours of administrators, missionaries, anthropologists, and others. Yet those whose knowledge is deepest are the first to admit that we still know only in part and darkly. Now it may be that, to achieve a fuller and clearer knowledge of the African mind, not only more study but additional methods of study are required. The main method up till now has necessarily been observation—observation of the behaviour of Africans in natural, everyday situations; and the result of this method has been the description of such behaviour. To this method we owe almost all of our present knowledge of the mentality of the African; and it seems likely that this must for long remain the chief source of our knowledge. It is not, however, the ideal scientific method. Our knowledge could probably be extended and made in some ways more precise by the method of studying the behaviour of Africans not in natural, everyday situations but in situations experimentally arranged and controlled. This method would result not merely in description but in measurement. Results obtained in controlled situations and expressed in quantitative terms would be results precise and verifiable. This method of study is not to be adopted prematurely, before the conditions of its technique can be fulfilled. But the advance of scientific understanding will sooner or later demand some such scientific method. One such method which is already being experimented with does involve the observation of the behaviour of Africans in controlled situations and does yield quantitative results. This is the method of mental testing.