Removing irrelevant information from working memory: a cognitive aging study with the modified Sternberg task.

Two experiments with a modified Sternberg recognition task explored the ability of young and old adults to remove irrelevant information from working memory. The task involved 2 memory sets, 1 of which was later cued as irrelevant. The recognition probe was presented at a variable time after the cue. Two indicators of inhibition, the setsize effect of the irrelevant set and the reaction time cost of intrusion probes (i.e., negative probes present in the irrelevant list), were dissociated. Irrelevant setsize effects lasted less than 1 s after the cue and did not differ between old and young adults. Intrusion costs lasted up to 5 s and were disproportionally large for old adults. With the additional requirement to remember both lists until after the probe, young adults' intrusion costs in Experiment 2 were equivalent to those of old adults in Experiment 1, but the setsize effects of the irrelevant set was larger. The results are compatible with a dual-process model of recognition in combination with a working-memory model distinguishing the focus of attention from the activated portion of long-term memory.