Linguistic positivity in American English: A large-scale diachronic study over the past two centuries

Abstract This study examines the shifts in linguistic positivity in general American English from the 1820s to the 2000s using a 430-million-token structured historical corpus. Furthermore, we investigate the effects of external environmental and internal psychological factors on linguistic positivity. Results showed a significant decline in both positive and negative expressions, indicating a broader societal move from emotionality to rationality in the USA over the past two centuries. Our findings also demonstrated that major wars, unemployment rates, and subjective happiness significantly affect changes in positivity. Notably, while major conflicts generally exert downward pressure on the linguistic positivity, broader historical, socio-cultural, and technological contexts can shape and at times counterbalance this effect, as evidenced by the contrasting linguistic responses to the Korean and Vietnam Wars. This study offers valuable insights into how language mirrors and responds to societal values and historical events. By detailing the interaction between language use and various influencing factors, our research suggests that combining word-level and sentence-level linguistic positivity bias analysis might offer potential applications for monitoring collective well-being and societal trends, enabling more responsive interventions.