While scientists generally try to stay out politics, letting evidence-based research to speak for itself, the strong division in American society has spread to science. How you view stem cell research, climate change, evolution and the role of science in setting public policy is one indicator of political leanings. Another can be the kind of science books you read with a new study finding that liberals and conservatives have very different tastes.

By analyzing millions of online purchases, researchers from Cornell, Yale and University of Chicago found that there are clear partisan preferences in how we buy books on scientific topics. Liberals opt for so-called "basic" sciences, like physics, astronomy and zoology, while conservatives go for applied and commercial sciences, such as medicine, criminology and geophysics.

“When we look at what science books they read and on what topics, liberals and conservatives are noticeably divided,” said the study’s co-author Professor Michael Macy from Cornell University. “They tend to not read the same books, and they don’t follow the same topics.”

Feng Shi, the study’s first author, proposed that liberals like “scientific puzzles” while conservatives prefer “problem-solving”.

One topic popular with both sides - books on dinosaurs. These were bought across the whole political spectrum.

For the study, researchers looked at purchase histories from Amazon and Barnes & Noble online stores, creating a dataset of 25 million “co-purchases” and 1.5 million books. They relied on the fact that these retailers recommend books to customers via book suggestion features like “Customers Who Bought This Item Also Bought”. That way the scientists could see what scientific texts were bought by those who also got liberal or conservative books.

The study’s authors think it’s likely that people who buy political books get science books to support their views rather than out of a general interest in science.

Is there a way science could help heal the division in the country? The study’s lead author Professor James Evans from University of Chicago is somewhat optimistic, thinking that people on all sides ultimately respect science. 

“Interest and respect for science remains high across political boundaries in the United States, suggesting that it could be a crucial bridge for crossing partisan divides in America,” said Professor Evans.

Professor Macy thinks their research highlights the fact that science communication needs to improve. 

“Our findings point to the need to communicate scientific consensus when it occurs, helping scientists find common cause with their audiences and adding public debate alongside scientific analysis to clarify the distinction between facts and values,” said Macy

While the study is illuminating, it  has some limitations, with political scientist Toby Bolsen cautioning that this research did not draw on a random sample of books, relying instead on how the online sellers categorized them. We also don’t know conclusively the motivations behind why individuals bought certain books.

You can read the new study in Nature Human Behavior.