In an attempt to better understand the reasons for old-age effects on task
switching performance, we fitted a quantitative model (Meiran, 2000a) to re
sults from an experiment comparing young and elderly participants. Modellin
g results indicate that the most pronounced effect of old age was in what c
an be broadly defined as the duration of the response selection. In additio
n, compared to young participants, the elderly tended to rely on learning f
rom the preceding trial, which improved their performance in single-task co
nditions but impaired it when the tasks switched frequently. Relatively mod
est effects of old age were found in the ability to selectively attend to t
he task relevant stimulus dimension and on the duration of processing stage
s preceding or following response selection.