Older and younger readers read sentences in which target words were masked 40 to 60 ms after fixation onset. Masking only the target word caused more disruption than did masking each word in the sentence, and this effect was stronger for the younger readers than for the older readers. Although older readers had longer eye fixations than did younger readers, the results indicated that the masking effect was comparable for the 2 groups. However, for both groups, how long the eyes remained in place was strongly influenced by the frequency of the fixated word (even though it had been rapidly replaced by the mask and was no longer there when the eyes did move). This is compelling evidence that for both older and younger readers, cognitive/lexical processing has a very strong influence on when the eyes move in reading.
from Psychology and Aging