To examine changes in semantic memory organization and use
during aging, we recorded event-related potentials as younger
and older adults listened to sentences ending with the expected
word, an unexpected word from the same semantic category, or
an unexpected word from a different category. Half of the contexts
were highly constraining. In both groups, expected words elicited
less negativity 300–500 ms (N400) than unexpected ones,
and unexpected words elicited smaller N400s when these were
categorically related. Whereas younger adults showed the greatest
N400 reduction to unexpected but related words in high constraint
contexts, older adults showed the opposite tendency. Thus, unlike
younger adults, older adults as a group do not seem to be using
context predictively. Older adults with higher verbal fluency
and larger vocabularies, however, showed the younger response
pattern, suggesting resource availability may offset certain
age-related changes.