Investigations of inhibition and interference in younger and older adults.

Previous work (Hasher, Stoltzfus, Zacks, & Rypma, 1991) suggested the existence of adult age-related differences in the ability to suppress or inhibit irrelevant information. This investigation explored age differences in the time course of suppression. Experiments 1 and 2 showed that younger adults demonstrate the same level of suppression at 300 as they do at 1,700 ms after a selection response. Older adults consistently show no suppression. Experiments 2 and 3 also examined the relationship between suppression and the degree to which distractors interfere with concurrent selection. The absence of a reliable relationship--both within and across age groups--together with other findings in the literature, raise questions about the function of suppression as a mechanism of concurrent selection. Another function, one that aids in the establishment of a coherent thought stream, is proposed.