Effects of stimulus properties and age on random-array letter cancellationtasks

Random-array letter cancellation tasks are commonly used in the clinical as sessment of visuospatial function. How stimulus properties and aging affect cancellation performance is not well understood. This study evaluated the effects of stimulus factors and age on 3 measures of cancellation performan ce. Thirty younger and 30 older adults each completed 12 cancellation forms that varied in paper size, stimulus density, and target-to-distractor (T/D ) ratio. Interactions between stimulus factors were identified for a calcul ated composite measure of speed and accuracy (effectiveness), a standardize d measure of the time required for completion of forms, and a standardized measure of the number of omission errors. The results showed complex intera ctions between stimulus factors that were different for each dependent vari able. These interactions were generally similar for both age groups. The fi ndings indicate that both stimulus properties and dependent variables must be carefully considered in the design and interpretation of cancellation pa radigms.