It is debated whether linguistic positivity bias (LPB) — the cross-cultural tendency to use more positive words than negative — results from a common cognitive underpinning or our environmental and cultural context.
Rumen Iliev, from the University of Michigan, and colleagues tackle the theoretical stalemate by looking at changes in positive word usage within a language over time. They use time-stamped texts from Google Books Ngrams and the New York Times to analyse LPB trends in American English over the last 200 years. They show that LPB has declined overall since 1800, which discounts the importance of universal cognition and, they suggest, aligns most strongly with a decline in social cohesion and prosociality in the United States. They find a significant association between LPB and casualty levels in war, economic performance, and measures of public happiness, suggesting that objective circumstances and subjective public mood drive its dynamics.
Analysing time-stamped historical texts is a powerful way to investigate evolving behaviours. The next step will be to look across other languages and historical events and tease apart the contribution of different contextual factors to LPB.