The study indicates a cultural evolution driven by increasing urbanization, greater reliance on technology and widespread availability of formal education, UCLA psychological scientist Patricia Greenfield says.
Greenfield measured culture-wide psychological change by examining the frequencies of specific words in more than 1.6 million English-language books published in the United States between 1800 and 2000.
Writing of her study in the journal Psychological Science, she said she found the words "choose" and "get" -- indicators of individualism and materialistic values that are adaptive in wealthier urban settings -- rose in frequency between 1800 and 2000.
In contrast, she said, words that reflect the social responsibilities that are adaptive in rural settings -- such as "obliged" and "give" -- declined over the same period.
"These replications indicate that the underlying concepts, not just word frequencies, were changing in importance over historical time," Greenfield said.
She said using Google's Ngram Viewer allowed her to study word usage in millions of source volumes quickly, something that wouldn't have been possible just a decade ago.
"The Google Ngram Viewer is a revolutionary tool in that it counts word frequencies in a million books in less than a second," she said. "Not only that, it's a publicly accessible tool. Anyone can go to the Google Ngram website and replicate all of my results!"
Examining culture-wide changes over hundreds of years allows for broader view of how cultural values are shifting, she said.
"This research shows that the currently discussed rise in individualism is not something recent, but has been going on for centuries as our society moved from a predominantly rural, low-tech environment to a predominantly urban, high-tech environment," she said.