Language (D)evolution in the Digital Age: Quantifying and Analyzing Linguistic Quality Over Time and Across Groups

Abstract

The proliferation of social media has ushered in a digital age, fundamentally altering the way in which people communicate in written form. As platforms like Reddit attract a growing share of the population, questions arise about whether there are observable shifts in lexical quality that constitute evolution or devolution. This thesis investigates the extent to which lexical quality in Reddit comments has changed over time and how these changes are associated with user commenting activity, within-user behavioral variation, and differences across age-based subreddit communities. Using comments and the associated metadata from r/teenagers, r/college, r/parenting, and r/retirement, this research constructs a corpus spanning the last decade of Reddit activity. Six lexical quality metrics, divided into measures of diversity and sophistication, are computed at the comment level. The methodology is similarly split into two parts: time-series analysis, employing baseline ordinary least squares and first-differenced autoregressive panel regressions, and cross-sectional analysis, employing weighted least squares, fixed effects panel, and mixed-effects regressions. The time-series models reveal limited evidence of directional change in lexical quality, with nonstationarity and autocorrelation constraining robust inference. The most consistent finding is a modest positive drift in lexical sophistication within r/teenagers and r/college. The user-level models yield clearer patterns, whereby more active users tend to exhibit greater lexical diversity, though the relationship with sophistication varies. At the subreddit level, age-based communities differ significantly, with r/parenting and r/retirement ranking highest in lexical diversity and r/college and r/teenagers ranking highest in lexical sophistication. To the extent that prior work exists, it relies on narrow topic selection, limited platform scope, or rudimentary metrics such as TTR and average word length; this thesis addresses these gaps by applying a broader and more methodologically rigorous suite of lexical measures across age-representative subreddit communities. Taken together, the results of this thesis suggest that Reddit lexical quality is shaped more by user behavior and community context than by the passage of time, and that online language is not monolithic but highly context-dependent.