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 performance have been studied extensively, many fundamental questions about cognitive ageing remain to be answered definitively. For example, what are the sources of age-related slowing? How much is working-memory capacity reduced in older adults? Is time-sharing ability lost with age? Answering such questions requires a unified computational theory that characterises the interactive operations of many component mental processes and integrates diverse data on cognitive ageing. Toward fulfilling this requirement, an executive-process interactive control (EPIC) architecture has been extended to model performance of both young and older adults. EPIC models yield accurate accounts 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 decrements may be attributable to conservative executive processes and inefficient task procedures rather than decreased "hardware" functionality. By clarifying and deepening such insights, unified computational theories like EPIC will help answer many questions about cognitive ageing.