Change in national mood shows up in patterns of word usage observed in historical databases

From the NYTimes:

In the wake of the election, it’s clear American society is fractured. Negative emotions are running amok, and countless words of anger and frustration have been spilled. If you were to analyze this news outlet for the ratio of positive emotional words to negative ones, would you find a dip linked to the events of the past few weeks?

It’s possible, suggests a study published last week in Proceedings of the National Academy of Sciences. Analyzing Google Books and The New York Times’s archives from the last 200 years, the researchers examined a curious phenomenon known as “positive linguistic bias,” which refers to people’s tendency to use more positive words than negative words. Though the bias is robust — and found consistently across cultures and languages — social scientists are at odds about what causes it.

In this study, the authors shed light on some possible new patterns behind the effect. Across two centuries’ of texts, they found that people’s preference for positive words varied with national mood, and declined during times of war and economic hardship.

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Linguistic positivity in historical texts reflects dynamic environmental and psychological factors

1. Rumen Iliev, 
2. Joe Hoover, 
3. Morteza Dehghani, and 
4. Robert Axelrod

Significance

For nearly 50 y social scientists have observed that across cultures and languages people use more positive words than negative words, a phenomenon referred to as “linguistic positivity bias” (LPB). Although scientists have proposed multiple explanations for this phenomenon—explanations that hinge on mechanisms ranging from cognitive biases to environmental factors—no consensus on the origins of LPB has been reached. In this research, we derive and test, via natural language processing and data aggregation, divergent predictions from dominant explanations of LPB by examining it across time. We find that LPB varies across time and therefore cannot be explained simply as the product of cognitive biases and, further, that these variations correspond to fluctuations in objective circumstances and subjective mood.

Abstract

People use more positive words than negative words. Referred to as “linguistic positivity bias” (LPB), this effect has been found across cultures and languages, prompting the conclusion that it is a panhuman tendency. However, although multiple competing explanations of LPB have been proposed, there is still no consensus on what mechanism(s) generate LPB or even on whether it is driven primarily by universal cognitive features or by environmental factors. In this work we propose that LPB has remained unresolved because previous research has neglected an essential dimension of language: time. In four studies conducted with two independent, time-stamped text corpora (Google books Ngrams and the New York Times), we found that LPB in American English has decreased during the last two centuries. We also observed dynamic fluctuations in LPB that were predicted by changes in objective environment, i.e., war and economic hardships, and by changes in national subjective happiness. In addition to providing evidence that LPB is a dynamic phenomenon, these results suggest that cognitive mechanisms alone cannot account for the observed dynamic fluctuations in LPB. At the least, LPB likely arises from multiple interacting mechanisms involving subjective, objective, and societal factors. In addition to having theoretical significance, our results demonstrate the value of newly available data sources in addressing long-standing scientific questions.

Published online before print November 21, 2016, doi:10.1073/pnas.1612058113 
PNAS November 21, 2016

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See my more recent post, Two-centuries decline in emotional expression in Anglophone fiction, which documents declining in LPB (though not in those terms) in fiction.