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Abstract:
Previous studies of orthographic neighborhood effects in
visual lexical decision tasks have shown a facilitatory effect of
increasing neighborhood density for words but an inhibitory effect
of increasing density for non-words. The current study examines the
effects of aging and frontal lobe functioning on lexical decision
performance. Young participants were compared to an elderly
population, neuropsychologically characterized for frontal lobe
functioning. Rates of false identification for nonwords did not
differ between young and older participants, however older
participants with lower frontal factors showed a significantly
higher rate of false positives than those with higher frontal
factors. Additionally, all groups showed an inhibitory effect of
increasing neighborhood density on correctly rejected nonwords,
while increasing neighborhood density seemed to have a facilitatory
effect for falsely identified nonwords. These results suggest that
successful rejection of nonwords involves the ability to inhibit
familiarity driven by orthographic similarity, which does not
decrease with aging per se, but rather with decreasing efficiency
of the frontal lobes. Elderly participants with lower frontal
functioning may rely more on familiarity and less on strategic
lexical search. These findings are consistent with the study of
Rapcsak, Glisky & Forster (1996) who reported a similar pattern
of lexical decision perfomance in a patient with focal frontal lobe
damage.
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