Last week, the author Michael Pollan expressed his concern over a piece in the New York Times, “A Race to Save the Orange by Altering Its DNA,” by Amy Harmon, about the potential use of genetic engineering to save oranges from certain disease-causing bacteria. “2 many industry talking pts,” he tweeted. His outburst was symptomatic of a wider suspicion of introducing genetically modified organisms into the food supply: Europeans refer to G.M.O.s as “frankenfood”; American companies, like Kashi, are censured for marketing products as “natural” when they contain genetically modified ingredients; and a fleet of cars, topped with giant, fish-shaped cartoon renditions of corn and tomatoes, is parading across the country to protest what it calls “fishy food.”

Psychologists have long observed that there is a continuum in what we perceive as natural or unnatural. As the psychologist Robert Sternberg wrote in 1982, the natural is what we find more familiar, while what we consider unnatural tends to be more novel—perceptually and experientially unfamiliar—and complex, meaning that more cognitive effort is required to understand it. The natural is seen as inherently positive; the unnatural is not. And anything that involves human manipulation is considered highly unnatural—like, say, G.M.O.s, even though genetically modified food already lines the shelves at grocery stores. As Michael Specter put it, “The history of agriculture is the history of humans breeding seeds and animals to produce traits we want in our crops and livestock.”

In a 2013 study, a group of Cornell University researchers found that how a food is labelled affects our perception of how it tastes, what its nutritional value is, and our willingness to pay for it. A hundred and fifteen shoppers at a local Ithaca mall were given three different food pairs. One item in each pair was labelled “organic” while the other was labelled “regular.” (In reality, the two items were identical, and both were organically produced.) The shoppers were then asked to rate the taste and the nutritional value of the products, as well as to guess at calorie counts and say how much they’d be willing to pay for each item. The researchers found that people's calorie estimates for the organic foods were consistently lower: an organic cookie, for example, was seen as approximately twenty-four per cent less caloric than a regular one. They thought the organic food tasted less artificial and was more nutritious over-all. They were also willing to pay somewhere between sixteen and twenty-three per cent more for the organic items. They were, essentially, experiencing something known as the halo effect, a phenomenon whereby one positive attribute of a person or thing colors other, unrelated characteristics in a positive light.

G.M.O.s, in contrast, suffer from a reverse halo effect, whereby one negative-seeming attribute (unnaturalness, in this case) skews over-all perception. In a 2005 study conducted at Maastricht University, in the Netherlands, researchers found that the more unnatural a genetically modified product seemed, the less likely it would be to gain acceptance. A hundred and forty-four University of Maastricht undergraduates were asked to visualize seven products, including butter, tomatoes, and fish fingers, and rate them on naturalness, health, and necessity. They were then asked to imagine genetically modified versions of the same products and respond to three questions: how morally justified it was to eat the food, how much they trusted it, and how natural they perceived it to be. As expected, the scientists found that the less natural a food product seemed, the less likely the participants were to trust or eat it. There was, however, an interesting caveat: if an original, non-modified product was made to seem less natural or more processed to begin with, people became far more likely to trust and accept the genetically modified equivalent.

The negative halo of G.M.O.s doesn’t just affect how we feel toward them; it also impacts how we evaluate their attending risks and benefits. As early as 1979, the psychologist Paul Slovic, who has been studying our perceptions of risk since the nineteen-fifties, pointed out that, when it comes to new, unknown technologies, data always loses out to emotion. For instance, people judge the risks of radiation from nuclear power plants to be much higher than those from medical X-rays—a conclusion that is not backed up by the data and is at odds with the advice of most risk experts—simply because nuclear power plants seem more foreign and inspire greater dread. What’s more, when we’re in a state of heightened emotion, we don’t weigh risks and benefits equally—risks take on an outsized impact and benefits begin to pale in comparison.

Once an initial opinion is formed, Slovic continues, it is very difficult to shift it with new evidence: the exact same piece of information—say, additional data on the effects of G.M.O.s on a natural ecosystem—can be interpreted in opposing ways, depending on your starting point. The public reaction to a study about the effects of genetically modified cotton on the environment bears out Slovic’s logic. After comparing environmental effects of non-modified to transgenic cotton, the researchers concluded that, while both types of crops had equally negative effects on arthropod populations, the G.M. cotton in fact had a higher end yield per each use of pesticide. When the results were reported, however, opponents of G.M.O.s tended to focus on the negative impact of the genetically modified crop, while failing to note the relevant comparisons. They concluded that genetic modification hurts the natural environment.

Slovic argues that three things stand in the way of a logical, analytical risk assessment of new technologies: our level of dread, our degree of familiarity (or lack thereof), and the number of people we believe the technology will affect. G.M.O.s are at the extreme of that scale, high in dread and possible impact, while being low in familiarity: though an estimated eighty per cent of packaged food in the U.S. contains G.M.O.s, only thirty-five per cent of the population thinks G.M.O.s are safe, according to one recent estimate, and only a quarter say they understand what genetic engineering of food actually entails.

It doesn’t help, either, that people tend to mistrust many of the sources of G.M.O. data. In addition to perceptions of risk, one of the single greatest elements that effects our acceptance of new technologies is trust. If we don’t trust a source implicitly, the quality of its information will make no difference in our evaluation; if we lack confidence in the entity doing the presenting our minds will discredit and discount it so quickly, we may as well not have seen it at all. And we tend not to trust the large corporations who tend to produce G.M.O.s.

Does that mean that G.M.O.s will always be subject to emotionally driven instead of data-driven assessments? Not necessarily. Time is on the side of increased rationality: the longer that genetic-modification technologies are in use, the more likely we are to begin to incorporate them into our sense of the familiar. As children are born into a world where genetic modification is more widespread, they may even begin to see it as more natural—and hence, be able to judge its impact with greater objectivity.

While the creep of familiarity might slowly breed acceptance, a more powerful driver is sheer need: in the 2005 Maastricht study, the experimenters discovered that if a product was perceived as more necessary—butter, for instance, as opposed to fish fingers—people were more willing to accept genetically modified alternatives. Necessity, it seems, can trump naturalness. This is true even for the people producing genetically modified food: the orange growers in Harmon’s were resistant to the idea of G.M. oranges, until they were confronted by the possibility of having no oranges left to grow. How much do you need that morning glass of orange juice?

Maria Konnikova is the author of the New York Times best-seller “Mastermind: How to Think Like Sherlock Holmes.” She has a Ph.D. in Psychology from Columbia University._

Photograph by Mark Elias/Bloomberg/Getty.