We humans have known for thousands of years that our mental abilities decline as we grow old but, as a formal academic discipline, the study of age-related changes in cognition began in the early 1950s and it is only during the last thirty years that we have begun to understand how these changes are related to the ageing of the brain and the central nervous system, and to differences in health and demographics. In recent decades governments around the world have been panicked into belated recognition of the consequences of rapidly increasing overpopulation and, particularly, of impending demographic imbalance due to increases in life expectancy. Especially in developed Western economies, but also increasingly in Asia, countries imminently face severe population ageing.Within twenty years the largest population cohort in many countries will be those aged over sixty-five, and the average age will be nearly fifty. In the UK, for example, by 2001 there were more people aged over sixty than under sixteen. And, in Japan, people over sixty-five are expected to make up more than one-quarter of the population by 2020. Moreover, the older population itself is ageing. The '80+ cohort' is the fastest-growing section of the older population and the United Nations estimate that the number of centenarians will increase fifteen-fold from approximately 145,000 in 1999 to 2.2 million by 2050.Governments have hoped that even if ageing cannot be abolished, it may be slowed so that dependency and loss of earning power can be delayed, and that better information about the progress of ageing will at least allow us to recognize and prepare for the implications of changes that we now cannot halt. They have consequently responded with funding initiatives for research that have produced an exponential growth in the numbers of investigators working in these fields, in the research students and post-doctorals that they train and supervise, in the undergraduate and graduate courses in cognitive gerontology, and in the neurophysiology and neuropsychology of ageing that they teach.MSc courses in cognitive gerontology are now common and courses in geriatric medicine have been promoted from a marginal to a core topic in medical schools. In short, cognitive and biological ageing has become a fast-growing and dynamic area of study and research, and the scale of this acceleration in growth makes this new four-volume collection in the "Psychology Press Major Works" series, Critical Concepts in Psychology, especially timely. A primary question is why we and all other complex animals and plants age, a question studied mainly by biologists, and Volume I ('Biological Bases of Ageing') includes key research on models for ethological and evolutionary ageing. It also takes full account of the body of work on the genetics of animal and human ageing and on genes that directly cause, or that interact with environmental influences to cause, individual differences in the rate of age-related changes.A quite distinct field of research has been the development of models for cognitive changes in the brain that are based entirely on behavioural evidence. Volume II ('Cognitive Ageing') gathers together the most important work on the search for the neuropsychological bases of cognitive ageing and in so doing helps to make sense of the rapid growth of developments in this area. The third volume in this collection ('Relating Cognitive Ageing to Brain Ageing') makes available the most significant recent research on how the amounts and time-courses of gross age-related changes in local areas of the brain affect cotemporaneous global and local changes in cognitive performance.Specific relationships between global brain changes and cognitive performance are explored, such as that between: increases in the incidence of white-matter lesions and progressive losses of memory and decision speed; cerebral blood flow and intelligence and information-processing speed; and memory impairment and losses of hippocampal volume. Key findings on the relationships between losses of tissue in the frontal lobes of the brain and changes in planning and intelligence is also gathered here, as is research on relationships between changes in neurotransmitter efficiency and in cognitive performance. Finally, the material collected in Volume IV ('The Effects of Health, Demographics and Social Conditions on Rates of Change in Old Age: Interpreting Data from Large Studies') examines how the methodology of longitudinal studies and cross-sectional studies affects the conclusions that can be reached from each and explores recent statistical models to analyse complex data sets.This volume does not simply describe some of the recent discoveries in statistical modelling and experimental design that enhance our use of longitudinal and cross-sectional data, but illustrates applications of these models to obtain new substantive contributions to our knowledge of how longevity - and so the maintenance of mental abilities in old age - are affected by declining health and the increasing burden of pathologies that accumulate as age advances; by the availability or absence of social and family support; by the extent and quality of social networks, and socio-economic advantage with its concomitant benefits of better education and access to medical care; and by diet and the use of tobacco, alcohol, and other drugs.With comprehensive introductions to each volume, newly written by the editor, which places the collected material in historical and scientific context, the "Psychology of Ageing" is destined to be a useful work of reference and valued by scholars, students, and practitioners as a primary research resource.