MOLAR AND LATENT MODELS OF COGNITIVE SLOWING - IMPLICATIONS FOR AGING, DEMENTIA, DEPRESSION, DEVELOPMENT, AND INTELLIGENCE

The time that it takes a group of participants to respond in simple co gnitive tasks varies systematically with the identity of the group. Fo r example, on most tasks, older adults take longer to respond than you nger adults. Similarly, on most tasks, younger children take longer to respond than mature children. More generally, response time has been found to vary reliably with a number of ether factors that differentia te groups of participants, including the levels of dementia, depressio n, and intelligence. For each factor, investigators have sought to det ermine whether the various mental processes are slowed identically as the level of impairment increases. They have based this determination largely on the relation between the overall response times of the rele vant groups. Here it is shown how one can base this determination on t he relation between the speeds of the individual latent or mental proc esses governing the performance of the target groups. Such a shift in emphasis has three important advantages: it reduces the possibility of falsely accepting or rejecting the hypothesis that all processes are slowed identically; it pinpoints the actual processes that are lengthe ned disproportionately when processes are not slowed identically; and it makes possible the rigorous testing of the effects of changes in sp eed on other dependent variables (e.g., accuracy).