People who hold the most extreme negative views about genetically modified (GM) foods think they know the most about GM food science, but they actually know the least, according to new research published in the journal Nature Human Behaviour.

“It’s always interesting, and not infrequent, that people with particularly strong opinions about a subject are less informed about it than those in the middle of the spectrum,” said Paul Rozin, professor in Penn’s department of psychology and an author on the paper. “People who fall more in the middle often more willingly consider positions alternative to their own.”

More than 2,000 adults in the US and Europe ranked their feelings about GM foods on a scale of 1 to 7, with 7 being the greatest apprehension. More than 90 percent reported some level of opposition or concern, despite a scientific consensus that GM foods are safe for human consumption and have the potential to provide significant benefits.

With the concern levels noted, the surveys then asked respondents how well they thought they understood genetically modified foods and tested their actual knowledge with true-false questions on general science and genetics. The researchers found that the more strongly people stated their opposition to such foods, the more they thought they knew about the topic but the lower they scored on the test.

“This result is perverse but is consistent with previous research on the psychology of extremism,” said Philip Fernbach, the study’s lead author and assistant professor of marketing at the University of Colorado Boulder. “Extreme views often stem from people feeling they understand complex topics better than they do.”

One potential consequence is that the people who know the least about important scientific issues may be likely to stay that way because they may not seek out or be open to new knowledge. “Changing peoples’ minds first requires them to appreciate what they don’t know,” said study co-author Nicholas Light, doctoral candidate at CU Boulder.

The researchers also explored other issues like gene therapy and climate-change denial. Though they found the same results for the former— that extreme opponents were less knowledgeable yet thought they knew more—the pattern did not emerge for the latter. The climate-change debate has become so politically polarized, the researchers hypothesize, that people’s attitudes depend more on which political group they affiliate with than how much they know about the issue.