Executive-process interactive control: A unified computational theory for answering 20 questions (and more) about cognitive ageing

Although the effects of ageing on human information processing and performa nce have been studied extensively, many fundamental questions about cogniti ve ageing remain to be answered definitively. For example, what are the sou rces of age-related slowing? How much is working-memory capacity reduced in older adults? Is time-sharing ability lost with age? Answering such questi ons requires a unified computational theory that characterises the interact ive operations of many component mental processes and integrates diverse da ta on cognitive ageing. Toward fulfilling this requirement, an executive-pr ocess interactive control (EPIC) architecture has been extended to model pe rformance of both young and older adults. EPIC models yield accurate accoun ts of ageing effects on reaction times and accuracy in basic dual-task and working-memory paradigms. From these accounts, it appears that time-sharing ability and working-memory capacity decrease relatively little until after 70 years of age. Before age 70, at least some apparent performance decreme nts may be attributable to conservative executive processes and inefficient task procedures rather than decreased "hardware" functionality. By clarify ing and deepening such insights, unified computational theories like EPIC w ill help answer many questions about cognitive ageing.