How taxonomic and thematic associations in semantic memory modulate recall in young through old-old adults

The aim of the current study was to investigate how the taxonomic and thematic organization of semantic long-term memory affected the recall performance of adults and older participants on a complex semantic working memory (SWM) task. Taxonomic and thematic classification are the two main systems used to organize knowledge: taxonomic information is hierarchically structured and typically independent of space and time, whereas thematically grouped concepts are horizontal and strictly context-dependent. Generally, thematic connections (more intuitive and experience-based) are formed earlier in development, while taxonomic links (more abstract and logic-based) are acquired later. We set out to explore whether this developmental pattern reverses with age, hypothesizing that the more complex form of memory organization (i.e., taxonomic) would play a lesser role in facilitating recall in the old, whereas thematic organization would be better preserved. Participants (aged 18 to 85 years) were asked to recall 60 words in sets of increasing span; the words were featured in lists organized to force a taxonomic association, a thematic association, or no semantic association. The results clearly showed that task accuracy varied more across age groups for taxonomically linked items than for thematically linked ones.