Cognitive Processes in Ageing

It has sometimes been uncritically assumed that involution mirrors development, so that individuals regress through developmental stages in a sort of inverse ‘decalagc’, A useful antidote is to remember that the intellectual and methodological problems of describing growing up and aging are very different. Understanding how children manage to acquire cognitive skills and modes of representation of the world that they could not previously attempt requires a quite different intellectual approach from understanding how older people cease to be capable of skills and modes of representation at which they once were superbly competent. However recent, reductionist general models for cognitive changes throughout the lifespan, while ignoring questions of changes in representational structure and skill acquisition and loss, propose that at any stage in the lifespan attainable levels of competence at all cognitive skills is limited by the current level of a single global factor which increases with developmental age, maintains a long plateau at maturity, and ebbs in senescence. Simplistic versions of this idea have directly equated this resource with a single, measurable performance index: the maximum speed with which individuals can make correct decisions in easy laboratory experiments. An attraction of this approach has been that it seems to provide a way of linking empirically measurable behavioural competence to potentially measurable functional property of the cognitive system and even to neurophysiological efficiency, providing, as one author his put it. a biological basis for intelligence’ (Eysenck, 1986). This chapter considers the historical evolution and current plausibility of this general model in three separate fields of research: individual differences in general intelligence, cognitive ageing and developmental psychology