[Intelligence change in adulthood]

At the present time we can summarize our results and interpret them normatively to the effect that until age sixty hardly any true changes in intelligence are to be expected as a result of aging; such changes are displayed by most people, however, during their seventies. It is furthermore important to refer to the fact that interindividual differences with regard to health and living conditions exert an influence on the development of intelligence (non-normative events, cf. Baltes and Willis, 1979). These are so significant, that one can hardly speak of a general process of intellectual development in adulthood. We must continue to investigate the multi-causal processes which result from interactions between dispositions and environmental experience.