Searching for the gap -- comparing young and older adults

Purposes: When do age-related differences in visual search performance occur and what causes them? Are they due to qualitative differences in processing information? Are older adults always worse? To answer these questions we decomposed search into components of (a) target-distractor discrimination, (b) attention sharing, (c) target detection & location accuracy, (d) confusions about target location, and (e) limitations due to decision noise vs. capacity. Methods: We tested 23 young adults (18 to 30 years old) and 25 older adults (65 to 79 years old). A Landolt C target was embedded among either O's or mirror-image Landolt C's. For search experiments, target-distractor discriminability was equated both across participants and visual search conditions; the set size was 2 or 4. Results: Older adults had significantly larger discrimination thresholds and required gap sizes approximately 3 times larger than did young adults. After equating target-distractor discriminability, however, older adults were better at sharing attention across spatial locations and showed less confusion about the target's location than young adults. For both age groups, performance was worse for the mirror-image search, suggesting capacity limitations, than for the simple feature search (Landolt C vs. O), where decision noise could explain performance. Conclusions: Although visual function may decline with age so that visual acuity becomes worse, one can overcome mild deficits by equating target-distractor discriminability in visual search. When this is done, older adults may perform as well or better than young adults on some components of visual search. Differences in search performance found between older and young adults suggest quantitative rather than qualitative factors. That is, age-related differences in search performance are not due to changes in demands placed on attention or in search strategies.