Abstract

Several decades of research into semantic memory have yielded two main perspectives as to how semantic memory may be organized. One hypothesis is that information is stored according to taxonomical categories (e.g., animals, objects); the other hypothesis suggests that information is stored according to featural attributes (e.g., functional and perceptual properties). Using a proactive interference (PI) paradigm, this study aimed to investigate these two hypotheses by contrasting the impact of categorical and featural cues on patterns of PI effects (i.e., buildup and release). Using the same stimuli and task, while examining recall performance and intrusion errors when featural and categorical information were opposed, allowed for a direct measure of the contribution of these two types of information for semantic organization. To explore semantic organization across the lifespan, 20 healthy younger and 20 healthy older participants were tested. Given that semantic memory deficits frequently occur in Alzheimer's disease (AD), the performance of the healthy older participants was also compared to 16 participants with AD to examine differences in semantic organization of featural and categorical information in individuals for whom there is a potential breakdown of semantic memory. All groups showed expected PI effects when stimuli were categorically cued. Participants also showed a release from PI when the featural cue changed (but the category remained the same). An unexpected release from PI effect was found in the featural PI continued condition in which the featural cue remained the same (e.g., USED FOR TRANSPORTATION) but there was an implicit switch in category (e.g., from OBJECTS to ANIMALS). The results are discussed in terms of the implications for the categorical and featural hypotheses of semantic memory organization.