I found the paper's interpretive commentary both less biased and more insightful than the OP, which is a short, opinionated blog post mentioning the paper. In

I found the paper's interpretive commentary both less biased and more insightful than the OP, which is a short, opinionated blog post mentioning the paper. In particular, these two paragraphs from the paper's section about "Potential Drivers" struck a chord with me: > What precisely caused the observed stagnation in the long-term trend around 1980 remains perhaps even more difficult to pinpoint. The late 1980s witnessed the start of the internet and its growing role in society. Perhaps more importantly, there could be a connection to tensions arising from neoliberal policies which were defended on rational arguments, while the economic fruits were reaped by an increasingly small fraction of societies. > In many languages the trends in sentiment- and intuition-related words accelerate around 2007. One possible explanation could be that the standards for inclusion in Google Books shifted from “being in a library Google had an agreement with” to “from a publisher that directly deposited with Google” after 2004 to 2007, thus affecting the corpus composition. The 2007 shift also coincides with the global financial crisis which may have had an impact. However, earlier economic crises such as the Great Depression (1929 to 1939) did not leave discernable marks on our indicators of book language. Perhaps significantly, 2007 was also roughly the start of a near-universal global surge of social media. This may be illustrated by plotting the dynamics of the word “Facebook” as a marker alongside the frequency of a set of intuition and rationality flag words in different languages. -- Paper: https://www.pnas.org/content/118/51/e2107848118 https://www.pnas.org/content/118/51/e2107848118 Abstract: The surge of post-truth political argumentation suggests that we are living in a special historical period when it comes to the balance between emotion and reasoning. To explore if this is indeed the case, we analyze language in millions of books covering the period from 1850 to 2019 represented in Google nGram data. We show that 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. 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.