CAN Knowledge Predict Acceptance? *Some* evidence for the Knowledge Deficit Hypothesis

In a perfect world, having more science knowledge would predict agreeing with scientific consensus on an issue. However, a lot of research in science communication (and other fields) have shown that this is not the case. In fact, the more people know about a topic, the more polarized they become. 

However, this may not be true for EVERYONE. That is, I suppose that people who have the most reason to disagree with scientific consensus will definitely find ways to do so; but, for those who don't care (e.g. political moderates, religious moderates), could we see a relationship between knowledge and acceptance of science information?

I was playing around with some data this morning from a project I am involved with in collaboration with Dan Kahan, Katie Carpenter, Laura Helft, Howard Hughes Medical Institute (HHMI), and Annenberg Public Policy Center (including my amazing fellow postdocs),  that examines the relationships between science curiosity, evolution belief, and engagement with documentaries on evolution. This data was collected from a nationally representative panel by YouGov.

To get people's stance on human evolution we ask (near the end of the survey):
True or False: Human beings, as we know them today, developed from an earlier species of animals.

About 38% of our sample (N=2,500) answer "false" on this item, which is pretty consistent with other nationally-representative polls asking about evolution. For instance, a 2007 Gallup/USA Today poll finds that 44% of people polled say evolution is either probably or definitely false. A 2011 Fox News Poll finds that 45% of people polled say that the biblical account of the origin of human life is most likely true (compared to 21% support for the theory of evolution as outlined by Darwin). And a 2014 poll by PRRI/AAR Religion, Values, & Climate Change Survey find that 41% of people polled either mostly or completely disagree that evolution is the best explanation for the origin of human life on earth.

Importantly, all of these items specifically ask about the origins of human life. Recent research suggests that people are more likely to endorse evolution when thinking about the origin of animal and plant life. 

The people most likely to be motivated to disagree with scientific consensus on evolution are those who are religious. Evolution is often contrasted with biblical accounts of the origins of human life such as creationism and/or intelligent design. For those who interpret their religious text literally, it is difficult to reconcile the theory of evolution with, for example, the account in Genesis. "

Thus, we wouldn't expect people who have strong religious beliefs to support the theory of evolution, no matter how much science knowledge they have.

Those who are not religious, on the other hand, have no reason to doubt the scientific consensus. So we wouldn't necessarily expect a correlation between science knowledge and acceptance of evolution there, either. 

Where a relationship between science knowledge and evolution may exist is in the middle---those who are somewhat religious, but are not so committed to a literal biblical interpretation that they would reject scientific evidence. But on the other hand, they are not so quick to automatically accept scientific consensus as those who are not religious would be, because they have an alternative hypothesis that is supported by their religious in-groups.  Thus, it is possible that we may see a relationship between accepting evolution and science knowledge here.

In our study, we used Dan's Ordinary Science Intelligence scale as a measurement of science knowledge. We also asked several items related to religiosity, such as how frequently people engage in prayer, how often they attend church services, whether they consider themselves "born-again", and how important their religion is to their daily lives. I combined these items into a index of "religiosity" using item response theory, which--when calculating scores of religiosity--takes into consideration that answering with higher values for some items (e.g., religious importance) are likely to indicate a higher level of religiosity than answering with higher values on other items (e.g., being "born again"). 

Then, I conducted logistic regression analyses in R predicting acceptance of human evolution (e.g., answering "true" to our evolution item) with ordinary science intelligence and religiosity as predictors. 

The regression revealed an interaction effect of religiosity and ordinary science intelligence. To graph this, I grouped religiosity into four categories: people who were in the bottom 25 percentile on religiosity, 25 to 50th percentile, 50th to 75th percentile, and 99th percentile (top 25%).

The raw data points are "jittered" so that you can more easily see the density of responses around particular points. The lines represent the predicted probability of accepting human evolution contingent on your level of science intelligence. The percentiles, as I said above, represent people's religiosity. 

You can see from the figure that science knowledge seems to predict acceptance of human evolution for people who are in the 25th to 50th percentile and for people who are in the 50th to 75th percentile. People who are in the lowest level of religiosity basically accept human evolution across most levels of science intelligence (discounting the small clump of participants who are really low on science knowledge).  For people who are the highest in religiosity, there is no relationship between science knowledge and accepting evolution. 

So, this data seems to show that knowledge *can* predict acceptance of evolution, but only for people who are not completely motivated to ignore scientific consensus, but have some reason to doubt it.