The use of words associated with rationality, such as “determine” and “conclusion,” rose systematically after 1850, while words related to human experience such as “feel” and “believe” declined. The analysis of language with Google Ngram of millions of books, in English and Spanish, fiction and nonfiction, during the period from 1850 to 2019 shows that this pattern reversed over the past decades.

This pattern reversed over the past decades, paralleled by a shift from a collectivistic to an individualistic focus as reflected, among other things, by the ratio of singular to plural pronouns such as “I”/”we” and “he”/”they.” Interpreting this synchronous sea change in book language remains challenging. However, as we show, the nature of this reversal occurs in fiction as well as nonfiction. Moreover, the pattern of change in the ratio between sentiment and rationality flag words since 1850 also occurs in New York Times articles, suggesting that it is not an artifact of the book corpora we analyzed. Finally, we show that word trends in books parallel trends in corresponding Google search terms, supporting the idea that changes in book language do in part reflect changes in interest. All in all, our results suggest that over the past decades, there has been a marked shift in public interest from the collective to the individual, and from rationality toward emotion.

Scheffer, Marten, Ingrid van de Leemput, Els Weinans, and Johan Bollen. ‘The Rise and Fall of Rationality in Language’. Proceedings of the National Academy of Sciences 118, no. 51 (21 December 2021). https://doi.org/10.1073/pnas.2107848118.

What precisely caused the observed change in the trend around 1980 remains a matter of speculation, but it aligns with evidence of stagnation in other much discussed longterm trends.