This study aims to clarify the influences of aging and AD on lexical-semantics by assigning a semantic priming paradigm. The following participants are included in the study: 30 young students, 22 early elderly, 19 late elderly, and 14 AD patients. The participants are asked to perform lexical decision tasks. Targets are high-frequency concrete words or nonwords. The primes are controlled with regard to their semantic relevance to the targets as follows: Association (e.g., king - lion), Superordination (beast - lion), Coordination (tiger - lion), Shared feature (eyes - lion), Distinctive feature (mane - lion), or Neutral (XXXX – lion). The participants have to decide whether the stimulus is a real word or not as correctly and as quickly as possible when the targets appeared on a monitor. As the Results, the mean reaction times (RTs) of the elderly groups are significantly longer than those of the young group, and the RTs of the AD group are even longer than those of the elderly groups. In the young and the elderly groups, the RTs for all the related-prime conditions are significantly shorter than those for the neutral-prime conditions (priming effects). The priming effects appears to be greater in the elderly groups. However, when the RTs are taken into consideration (priming rates), the gains are equivalent among young and elderly groups. In the AD group, priming effects are not observed, and noticeable individual differences in the priming rate are seen. The above findings suggest that lexical-semantics are generally preserved from aging. We also discusses that lexical-semantics are impaired in AD, and the diversity of the impairments may be the essence of AD
