Speed and knowledge as determinants of adult age differences in verbal tasks.

Two studies were conducted to determine the relative importance of processing speed and knowledge as predictors of performance in simple verbal tasks within samples of young and old adults. Eight different criterion tasks were investigated, and performance on each was found to be significantly related both to speed of processing and to quantity of word knowledge. It was also discovered that although young adults were faster than old adults and that old adults were equal or superior to young adults in relevant knowledge, the same regression equations could be used to predict criterion performance in both groups. These results therefore suggest that any age-related compensation that exists in these tasks is rather weak, in the sense that speed and knowledge appear to have the same importance in young and old adults, and only the average levels of the predictors differ as a function of age.