The authors used a lexical-decision task in 3 different experiments to
examine whether age differences in word recognition were consistent a
cross processing stage. In all experiments, word frequency and length
were manipulated. In Experiments 1 and 2, encoding difficulty was vari
ed, and in Experiment 3, response selection difficulty was varied. In
all 3 experiments, there were no age differences for word frequency. H
owever, in Experiments 1 and 2, older adults showed a larger decrement
for encoding. In Experiment 3, age differences were larger when respo
nse selection load increased. These results suggest that age differenc
es in word recognition occur because older adults exhibit primarily pe
ripheral- rather than central-processing decrements. The implications
of these data for generalized and localized slowing models are discuss
ed.