REACTION-TIME MEASURES OF SPEED OF PROCESSING - SPEED OF RESPONSE SELECTION INCREASES WITH AGE BUT SPEED OF STIMULUS CATEGORIZATION DOES NOT

We report an experiment that investigates the relationship between spe ed of information processing and development. The goal of the experime nt was to compare developmental changes at two stages of processing--r esponse selection and stimulus categorization. The experiment compared developmental change on three kinds of reaction time task. The first was a standard Jensen (1982) procedure which separates the decision an d motor components of reaction time, the second was a modification of this procedure suggested by Smith & Carew (1987) to control for possib le anticipatory strategies, and the third was a more traditional react ion time task where each stimulus is paired with a unique response (li ghts-to-keys). Age changes in speed of information processing were fou nd for the lights-to-keys task but not for either of the Jensen tasks. We argue that this is because the lights-to-keys task taps response s election factors that change with age and that are orthogonal to diffe rences in speed of stimulus categorization indexed by the standard Jen sen task. If the latter is taken as the purer index of speed of proces sing then we conclude that speed of processing does not change with ag e.