THE STRUCTURAL ORGANIZATION OF THE MENTAL LEXICON AND ITS CONTRIBUTION TO AGE-RELATED DECLINES IN SPOKEN-WORD RECOGNITION

Three experiments were conducted within the framework of the Neighborh ood Activation Model of spoken-word recognition to study how the struc tural organization of the mental lexicon may contribute to age-related declines in spoken-language processing. Experiment 1 showed that the number and frequency of words that are phonetically similar to a targe t word had differential effects on perceptual identification in older and younger adults, with older adults being particularly disadvantaged in identifying hard words (words phonetically similar to many other h igh-frequency words). Experiment 2 showed that age-related deficits in the ability to identify hard words remained under conditions in which performance for a set of easy words (items phonetically similar to re latively few other low-frequency words) was the same for older and you nger adults. In Experiment 3, reducing the resources available for ide ntification by changing from single to multiple talkers reduced word r ecognition more among older than younger adults. Diminished cognitive resources, impaired inhibitory control, and increased general slowing are discussed as explanations for the results.