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How do people respond to scientific information about GMOs and climate change?

The journal Food Policy just published a paper by Brandon McFadden and me that explores how consumers respond to scientific information about genetically engineered foods and about climate change.  The paper was motivated by some previous work we'd done where we found that people didn't always respond as anticipated to television advertisements encouraging them to vote for or against mandatory labels on GMOs.  

In this study, respondents were shown a collection of statements from authoritative scientific bodies (like the National Academies of Science and United Nations) about the safety of eating approved GMOs or the risk of climate change.  Then we asked respondents whether they were more or less likely to believe GMOs were safe to eat or whether the earth was warming more than it would have otherwise due to human activities.    

We classified people as "conservative" (if they stuck with their prior beliefs regardless of the information), "convergent" (if they changed their beliefs in a way consistent with the scientific information), or "divergent" (if they changed their beliefs in a way inconsistent with the scientific information). 

We then explored the factors that explained how people responded to the information.  As it turns out, one of the most important factors determining how you respond to information is your prior belief.  If your priors were that GMOs were safe to eat and that global warming was occurring, you were more likely to find the information credible and respond in a "rational" (or Bayesian updating) way.  

Here are a couple graphs from the paper illustrating that result (where believers already tended to believe the information contained in the scientific statements and deniers did not).  As the results below show, the "deniers" were more likely to be "divergent" - that is, the provision scientific information caused them to be more likely to believe the opposite of the message conveyed in the scientific information.  

We also explored a host of other psychological factors that influenced how people responded to scientific information.  Here's the abstract:

“The ability of scientific knowledge to contribute to public debate about societal risks depends on how the public assimilates information resulting from the scientific community. Bayesian decision theory assumes that people update a belief by allocating weights to a prior belief and new information to form a posterior belief. The purpose of this study was to determine the effects of prior beliefs on assimilation of scientific information and test several hypotheses about the manner in which people process scientific information on genetically modified food and global warming. Results indicated that assimilation of information is dependent on prior beliefs and that the failure to converge a posterior belief to information is a result of several factors including: misinterpreting information, illusionary correlations, selectively scrutinizing information, information-processing problems, knowledge, political affiliation, and cognitive function.”

An excerpt from the conclusions:

“Participants who misinterpreted the information provided did not converge posterior beliefs to the information. Rabin and Schrag (1999) asserted that people suffering from confirmation bias misinterpret evidence to conform to a prior belief. The results here confirmed that people who misinterpreted information did indeed exhibit confirmation, as well as people who conserved a prior belief. This is more evidence that assuming optimal Bayesian updating may only be appropriate when new information is somewhat aligned with a prior belief.”

Food Demand Survey - May 2015

The results of the May 2015 edition of the Food Demand Survey (FooDS) are now in.

Results reveal mixed changes in willingness-to-pay for disaggregate meat products.  However, stated purchase intentions for beef, pork, and chicken were all higher than last month as were expectations of price increases, suggesting an uptick in demand for meat.

As was the case in April, this month we again noticed an uptick in awareness of news about bird flu and an increase in concern about the issue.  That's two months in a row of notable increases in this issue.

We added several new ad hoc questions to the survey this month.  

The first set of questions were in response to the spreading avian influenza (bird flu) problem.  I've had several media inquiries (probably in response to this post) about the potential economic impacts of the outbreak.  One questions is whether domestic consumer demand for poultry and eggs will dampen in response to the outbreak.  My understanding is that avian influenza does not pose a human health or food safety risk, but of course that doesn't mean consumers believe the same.  As the regular tracking questions mentioned above suggest, consumers are becoming aware of the issue.  To delve into it a bit more, we added two agree/disagree questions. 

About 23% of respondents agreed or strongly agreed that they plan to eat less turkey and eggs because of the outbreak of avian influenza, and another 32% say they're concerned about the turkey and eggs they eat.  That's far from a majority, but it might be a large enough to affect demand.  Whether these beliefs will ultimately manifest themselves in the supermarket remains to be seen.  

A second set of questions were added to delve a bit deeper into the issue of labeling of GMO foods.  Yes, this an issue that has been much studied, and yes, consumer's answers to the question can't entirely be taken at face value (as my questions on preferences for DNA labeling have shown).  But, there seems to be some activity related to a GMO federal labeling initiative re-introduced by US Congressman Mike Pompeo from Kansas and others (see this for some discussion and background).  The bill has food industry support and it would move authority for GMO labeling to the FDA (and away from the states) and would only require labels if the FDA determines a health or safety risk.   

The first question asked: “Which of the following best describes your position on labeling of genetically engineered food?” Over half of the respondents answered, “Food companies should be required to label genetically engineered food in all circumstances”.  The other 46% of respondents expressed a more nuanced view.  About one fifth thought labeling should only be required if there is a health or safety risk and another 18% did not have a strong position. The remaining 6.5% of respondents stated “In general, food companies should not be required to label genetically engineered food but voluntary labels are permitted”.

Secondly, participants were asked: “How should the issue of mandatory labeling of genetically engineered food be decided?”  They could choose from one of six options.  


The majority, 61%, of the respondents stated “by the U.S. Food and Drug Administration (FDA)”.  Just over 10% of repspondents stated “I don’t know” and only 5% of respondents stated “by ballot initiatives in each state”.

Finally, the third question asked: “To what extent do you agree or disagree with each of the following statements?”  Participants were asked to rate each statement on a scale of 1 to 5 where 1 = strongly disagree, 3=neither agree nor disagree, and 5 = strongly agree.


Respondents rated the statement “In general, I support mandatory labeling or genetically engineered foods” the highest out of the nine statements with a score of 3.86.  The statement “Seeing a label indicating the presence of genetically engineered ingredients on a food product would increase the likelihood I’d buy the product” rated the the lowest of the nine statements with a score of 2.84. 

Thanks to David Ropeik who suggested a couple of the questions below related to effect of labels on perceptions on choice. 

Chipotle and GMOs

Last week I mentioned Chipotle's decision to go semi-non-GMO when discussing consumer sovereignty vs. scientific integrity.  

I've been astounded at the voluminous, and nearly unanimous, backlash against Chipotle's decision in the media.   The criticism has ranged from discussions on:

  • The inconsistency of Chipotle's position.  They're getting rid of GMOs in some foods but not others (particularly soda and in all likelihood the feed used for the animals).
  • The hypocrisy of claiming to look out for customer's health while selling 1,600 calorie burritos.
  • Ignoring evidence on relative risk of herbicides.  One of Chipotle's stated reasons for moving away from soybean oil toward sunflower oil is that that most soybeans use biotech varieties that are resistant to the herbicide glyphosate, which Chipotle implies is problematic.  However, as many commentators have pointed out the herbicides used on sunflowers are likely more toxic and are equally connected (if not more now that glyphosate is off patent) to "big agribusiness".
  • And, generally stoking fear when the scientific evidence suggest there is none.  That is, they've been roundly criticized for being anti-science. 

Amazingly, I haven't seen one story in a major media outlet that has applauded Chipotle's move. Mary Mangan, aka @mem_somerville, has compiled a list of stories that have appeared on the issue.  Negative stories or editorials have been run in the New York Magazine, Wall Street Journal, Slate, Chicago Tribune, LA Times, Washington Post, and many others.  

I'm not sure what these developments imply for the politics surrounding GMO labeling (an issue which appears to be gaining a bit more traction in the US House of Representatives), but I'm almost certain this wasn't the outcome Chipotle was expecting.  You might be able to pick up a bit of market share in the short run by stoking fear and paranoia, but when science isn't on your side, it's bound to catch up with you in the long run.  

Food Demand Survey (FooDS) - February 2015

The newest release of the Feed Demand Survey (FooDS) is now out.

Compared to last month, we found 8% to 15% jumps in willingness-to-pay (WTP) for both beef products (steak and hamburger) and for deli ham.  There was also a sizable increase (9%) in spending on food away from home relative to last month.  

Following up on all the controversy surrounding last month's question on DNA labeling, we delved into the issue again, but this time in a slightly different way.  First, we asked the question in isolation (on a single page by itself), rather than in a list with other food policy issues (Ben Lillie had argued in a blog post following our last result our result was at least partially due tot he fact that the DNA label issue appeared in a list with other issues).  Secondly, the question was reworded so that it was clear that the label was meant to indicate the presence absence of DNA.  The precise wording was, "Do you support or oppose mandatory labels on foods that would indicate the presence or absence of DNA?"  The choice options were support or oppose (the order of which was randomized across respondents). We found essentially the same result as before, 83.5% of respondents supported DNA labeling (note: sample size is 1,001, sampling error is +/-3%, sample weighted to match the population demographics).   

I also looked at the demographic breakdown of those who answered support vs. oppose.  For those who supported, 43%  had a college degree, 49% were female, 46% were Democrats, and 20% were Republications; for those who opposed, 58% had a college degree, 45% were female, 38% were Democrats, and 28% were Republicans. Education and political party affiliation appear to be partial drivers of support for DNA labeling.

Then, on a following page, we asked a number of true/false questions to gauge people's knowledge about DNA, genetics, etc.

Most respondents, 64.6%, correctly knew it was false that "ordinary tomatoes do not contain genes while genetically modified tomatoes do."  However, a remarkably high number of respondents, 52%, said it was false that "all vegetables contain DNA", and only 58.6% that it was true that "yeast for brewing beer contains living organisms."