In prior sociolinguistic research, speaker age has been considered the principal correlate of language change, but it 'has not yet been explicitly studied as a sociolinguistic variable' (Eckert 19 9 7: 16 7). Consequently, little is known about how language varies across the life span. The present study employs key word analysis on a large corpus of casual conversation in American English to explore age-based linguistic variation in spontaneous conversation. Analyses of the key words point to two major patterns of age-based lexico-grammatical variation: use of slang, and use of stance and involvement markers. Younger speakers' talk is characterized by an unusually frequent use of slang and swear words, and by a marked use of features indexing speaker's stance and emotional involvement, including intensifiers, stance adverbs, discourse markers, personal pronouns, and attitudinal adjectives; older speakers favor modals. These patterns are suggestive of functional differences in the discourse of youth and adults. It is argued that the expression of personal stance is more explicit and plays a key role in younger speakers' discourse.
