Abstract Word Dropout and Cross-Speaker Misalignment of Word Concreteness are Features of Conversation in Aging

Our earliest acquired words tend to reference concrete objects that can be seen, heard, touched, and felt. One hallmark of language maturation involves an ‘abstractness shift’ where language is used to convey intangible mental states, emotions, and ideas. Much of our understanding of the trajectory of concreteness in language development ends at early adolescence and is informed by studies of comprehension. We investigated concreteness effects in language production across the span of adulthood with a focus on conversation. We tested two competing hypotheses about abstract word use in conversation as a function of normal aging. The first hypothesis is that a steady accrual of vocabulary knowledge over the lifespan will confer a more expansive abstract lexicon and that older adults will in turn produce more abstract words in conversation. An alternative hypothesis is that aging gradually compromises executive resources that impact abstract word retrieval, leading to a concreteness bias in 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) using a novel computational algorithm (ConversationAlign). Aging was associated with abstract word dropout, a finding that is consistent with the hypothesis that high processing demands of conversation (e.g., alignment, topic maintenance) bias lexical retrieval toward concrete word use. We discuss the significance of these results for understanding intergenerational communication and relationships between aging, executive functioning, and lexical retrieval in high-level discourse.