Abstract word dropout and cross-speaker misalignment of word concreteness are features of conversation in aging

Language development is significant for an abstractness shift where the early concrete lexicon of childhood steadily expands to incorporate abstract concepts (e.g., mental states, emotions, ideas). Much remains to be learned about the trajectories of concrete versus abstract words across the span of development, especially within the domain of discourse production. We investigated the prevalence of abstract word use in dyadic conversations between adults of different ages (range 18-66). Our aim was to adjudicate between two opposing trajectories of language use in normal cognitive aging. The vocabulary growth perspective holds that aging is associated with a steady accrual of vocabulary knowledge resulting in greater lexical diversity and a larger pool of abstract words to draw upon in conversation. In contrast, resource pruning predicts the opposite trajectory such that age-associated gains in vocabulary acquisition are offset by diminished executive resources. Since abstract words tend to have higher lexical retrieval demands than concrete words, normal aging will result in an apparent dropout of abstract words. Moreover, this concreteness effect will be amplified within a resource-intensive communication modality such as conversation. We analyzed distributions of abstract and concrete words and cross-speaker alignment within unscripted conversations between adults of different ages (N = 1565 conversations, >8 million words, age range 19-66). Aging was associated with abstract word dropout, and misalignment between conversation partners on concreteness expanded in parallel with their respective age differences. These results add to a growing body of research that implicates executive functioning in controlled lexical retrieval of abstract words. We discuss significance of these results for understanding intergenerational communication and relationships between aging, executive functioning, and lexical retrieval in high-level discourse.