The use of "emotional" words in novels has fallen steadily over the past century - with the exception of words associated with fear.
Recently published research from the UK universities of Bristol, Sheffield and Durham explored how often "mood" words were used by studying more than 5 million digitised books.
The list of words was divided into six categories: anger, disgust, fear, joy, sadness and surprise. These categories were also used as the basis of an earlier study on contemporary "mood swings", as expressed in tweets that were collected in the UK over two years.
"We thought it would be interesting to apply the same methodology to different media, especially on a larger timescale," says Dr Alberto Acerbi, a Newton fellow in the department of archaeology and anthropology at the University of Bristol, and lead author of the paper.
The study also determined when British and American English began to diverge stylistically, with language in the US remaining more emotional. As Winston Churchill put it: "Americans and British are one people separated only by a common language."
"We were initially surprised to see how well periods of positive and negative moods correlated with historical events," Acerbi says. "The Second World War, for example, is marked by a distinct increase in words related to sadness, and a correspondent decrease in words related to joy."
The researchers found that American and British English appeared to begin to diverge in the 1960s.
"We don't know exactly what happened," Professor Alex Bentley, co-author of the study, says. "We can only speculate whether this was connected to the baby boom or to the rise of counter-culture.
"In the US, baby boomers grew up in the greatest period of economic prosperity of the century, whereas the British baby boomers grew up in a post-war recovery period. Perhaps 'emotionalism' was a luxury of economic growth."
A remaining question, the authors say, is whether word usage represents real behaviour in a population - or possibly an absence of that behaviour, which is then increasingly played out through literary fiction.
In other words, according to the authors, books may not reflect the real population - or its use of words in everyday language - any more than catwalk models reflect the average body shape.
But the researchers did conclude that not only has technology revolutionised our understanding of culture, it can also help us to see how this changes over time.
Who were the baby boomers? What were the key influences on that generation in the US and in Britain?
What is the difference between formal language and colloquial language?
Choose a sentiment. Explain how you would communicate it verbally to your friends and how you would communicate it in a letter to your employer or teacher.
When do we use emotive language? How much is the language we use influenced by mood?