AGING AND THE SPEED ACCURACY RELATION IN VISUAL-SEARCH - EVIDENCE FORAN ACCUMULATOR MODEL

Two models of performance in visual classification tasks, the fast-gue ss model and the accumulator model, offer contrasting accounts of the relation between speed and accuracy. We attempted to distinguish these models in the context of age-related changes in visual search perform ance. Twenty-four young adults (mean age 21.50 years) and 24 older adu lts (mean age 66.17 years) performed a visual search task requiring th e detection of an upright L among rotated L's. The results supported t he accumulator model, in that mean reaction time (RT) was higher for e rror responses than for correct responses, and there was a positive re lation between RT and error rate. Both of these effects were more pron ounced for older adults than for young adults, even when visual acuity was covaried statistically. We conclude that age-related changes in v isual search performance involve a decline in the efficiency of sampli ng the amount of evidence necessary to exceed a decision criterion.