When it comes to buying books online, Americans appear to stand united in our wide-ranging passions, including for science. But on closer inspection, our book-buying habits suggest that, when it comes to choosing science titles, we remain a country divided by politics.

Sorting through a database of millions of online book purchases, the authors of a new study have found that when purchasers of a political book also ordered a book on a scientific subject, some pretty clear partisan divisions emerged.

Customers who bought a political book aligned with a liberal viewpoint tended to prefer basic science, such as physics, astronomy or zoology, when also ordering a science book. Customers who bought a political book aligned with a conservative political viewpoint were more likely to choose a science book in an “applied” science field such as criminology, organic chemistry, medicine or geophysics.

The authors, a team of social scientists from University of Chicago, Yale and Cornell University, reported their findings Monday in the journal Nature Human Behaviour. While their research is a first cut at the subject, it suggests that Americans, who long saw science as a force that transcended politics, now often see it through partisan eyes.


Just as social media platforms such as Facebook have been charged with helping Americans build their own political “echo chambers,” the authors suggest that booksellers’ online marketing gambits may have drawn scientific books into “the ‘Big Sort’ of American politics — the tendency to cluster in like-minded communities.”

To glean these political patterns in science reading, they scoured Amazon and Barnes & Noble websites in the spring of 2013, using the automated algorithms designed to sell more books to discern patterns of “co-purchasing.”

They were able to tease out some revealing patterns.

To distinguish between “basic” and “applied” sciences and subfields, the researchers largely relied on distinctions made by librarians in categorizing scientific books. That judgment largely turns on the degree to which works in a given scientific field are cited in patents. For instance, organic chemistry research is routinely cited in these commercial documents, making this an applied science.


“Basic” sciences, for the current study’s purposes, are those which are “largely driven by curiosity and basic scientific concerns.” Included among the basic sciences label are such disciplines as zoology and anthropology.

Disciplines such as medicine and law (which lie at the most “applied” ends of the life sciences and social sciences, respectively) attracted readers at the conservative end of the spectrum. At the liberal end of the spectrum, basic science texts in fields like anthropology and astronomy tended to attract more readers.

“A possible interpretation is that scientific puzzles appeal more to the left, while problem- solving appeals more to the right,” wrote the authors.

Even after excluding textbooks and books written primarily for academic audiences from their analysis, the authors’ findings held. And when buyers of political books also bought books in the categories of art, sports, literature or religion, the researchers did not discern patterns as clearly partisan as they did with science books.


There were, of course, science fields to which partisans from both sides gravitated: books on paleontology, for instance, attracted buyers who also bought political books ranging across the political divide.

But even in these scientific neutral zones, buyers of left-leaning political books chose different titles than did buyers of right-leaning books. The researchers found that buyers of politically conservative books tend to purchase the same scientific books that other conservative book-buyers buy, but not a wide range of other books in the scientific discipline that they seem to be interested in.

Buyers of liberal books tend to buy a more diverse set of science books. The science books they buy are more likely to include books that are frequently co-purchased with other books in the same scientific discipline.

“Within disciplines, ‘red’ books tend to be co-purchased with a narrower subset of science books on the periphery of the discipline,” the authors wrote. “We conclude that the political left and right share an interest in science in general, but not science in particular.”


So how did the researchers glean all this?

They cleverly exploited the booksellers’ automated algorithms designed to sell customers more books (essentially the line of products advertised under the heading, “Customers who bought this item also bought...”). First, they found 3,714 books that were either by prominent politicians (including Barack Obama and Mitt Romney) or that were pitched under headings such as “Liberalism and Conservatism.”

The researchers assigned each title a place on the right or left of the political spectrum, or ideologically indeterminate. Then, they searched for each of those books to see whether the buy-more-books algorithm offered up any books in the life sciences, physical sciences, social sciences or humanities.

Yale social scientist Dan Kahan, who studies science interest and skepticism, and how American politics and science collide, called the new study “very enlightening.”


Kahan, who was not involved with the current research, said the new study can’t explain whether an individual’s personal interests in scientific subjects shape his or her views on current science controversies. But the patterns the study revealed can now motivate research that ties individual interest in different types of science books to opinions on contested science issues.

And understanding that relationship “would be a big advance in knowledge,” he said.

melissa.healy@latimes.com

@LATMelissaHealy