Books have gotten less "emotional" and scarier over the past 40 years, and the emotions conveyed in books correspond closely with world events, according to an analysis by researchers at England's University of Bristol.
The researchers analyzed authors' word choices using Google books, which contains about 4 percent of all books published in the 20th century and found that authors began using words relating to joy, anger and sadness less starting in the 1970s and began using words relating to fear (such as "horrible, terrified, creep and scary") much more often.
According to Alberto Acerbi, lead author of the paper, trends in emotional words often correspond closely with major world events. Acerbi says he identified two "happy periods" in the data—during the roaring 1920s and the 1960s—but also found "sad" periods during periods of war.
"We were very surprised to see how well moods in books corresponded with historical events of the 20th century," he says. "Almost exactly with the commencement of the U.S. Great Depression, there is a very clear peak in "sadness" that culminates with the Second World War."
The study also found that British authors started using fewer words corresponding to emotions than American authors in the 1960s, a "general stylistic change" that has continued to the present in each country.
"In England in the 1960s, among the most successful novels were espionage books and thrillers, in which emotional restraint was a trademark," he says. Conversely, "In the 1960s, emotions were part of pioneering American writing. Kurt Vonnegut explored emotional themes of desire, destiny and happiness. Other American authors explored civil rights, like James Baldwin or Harper Lee."