Extreme opponents of genetically modified foods know the least but think they know the most.

There is widespread agreement among scientists that genetically modified foods are safe to consume1,2 and have the potential to provide substantial benefits to humankind3 . However, many people still harbour concerns about them or oppose their use4,5 . In a nationally representative sample of US adults, we find that as extremity of opposition to and concern about genetically modified foods increases, objective knowledge about science and genetics decreases, but perceived understanding of genetically modified foods increases. Extreme opponents know the least, but think they know the most. Moreover, the relationship between self-assessed and objective knowledge shifts from positive to negative at high levels of opposition. Similar results were obtained in a parallel study with representative samples from the United States, France and Germany, and in a study testing attitudes about a medical application of genetic engineering technology (gene therapy). This pattern did not emerge, however, for attitudes and beliefs about climate change.