This project will identify mechanisms underlying age-related changes in cognition and action. Two general hypotheses as to the specific nature of these mechanisms will guide the research. Under one hypothesis, inhibitory processes become less effective in older adults, while under the other, age weakens connections between nodes or representations in memory, so that activity transmitted from one unit to another declines with age. Empirical support for one or the other hypothesis that will emerge from the proposed research promises to have a major impact on the field, and to increase our understanding of basic processes underlying comprehension, memory, and production of language and other cognitive skills. By examining a set of phenomena that have rarely if ever been examined in older adults, e.g., misspelling, repetition deafness, semantic blindness, comprehension of negative sentences and ambiguous words, microslips, action errors, and the ability to describe actions while producing them, the project promises to fill several gaps in our knowledge. Moreover, the projects focuses on tasks and phenomena where older adults are predicted to exhibit superior performance to young adults have been the main focus. The project also carries practical implications for many areas of cognitive psychology, from the everyday difficulties of older adults in learning and using new information, to teaching techniques for adults education programs. Three sets of studies are proposed. The first set investigates effects of age on fundamental components of language comprehension and reasoning. A second set of studies examines age-related changes in the ability of encode information for later recall. A third set os studies examines effects of aging on errors in speech and everyday actions of young and older adults.