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Dermot Hayes, Economics, (515) 294-6185
Teddi Barron, News Service, (515) 294-4778


AMES, Iowa -- When favorable and unfavorable statements about a new food technology--like irradiation or genetic modification--are presented simultaneously, consumers will accept the unfavorable message and avoid the new food.

That was the finding of an Iowa State University study on the impact of information on the demand for food irradiation. The research will be published in The Journal of Risk and Uncertainty.

The research is the first controlled experimental study to examine effects of a simultaneous presentation of both negative and positive information on revealed values.

Economist Dermot Hayes, Pioneer Hi-Bred International Chair in Agribusiness at Iowa State, led the research team that included economists John Fox, Kansas State University, and Jason Shogren, University of Wyoming.

The researchers were concerned with the relative and combined effects of different descriptions of a new food technology.

"In our study, we looked at how consumers respond to the contradictory descriptions of food irradiation like those that appear in the media," Hayes said.

"In at least two recent controversies, irradiation and genetic modification, the public has had to decide between opposing assertions made about food safety by advocacy groups and by scientific experts," Hayes said.

"Our results suggest that when advocacy groups indicate that new food technologies are unsafe, consumers avoid these foods even if scientific bodies say the technologies are safe," he said.

The researchers used an experiment designed to resemble an auction with several rounds of sealed bidding on a food product. When new information about the food was introduced, participants could re-evaluate their preferences and adjust their bid, giving researchers insight into the participants' willingness-to-pay values.

The 87 participants in the experiment were primary food shoppers recruited from a random sample. They were assigned to three treatment groups, each group testing the effect of the introduction of positive information, negative information, or both positive and negative information.

Participants in all groups received descriptions of two pork sandwiches. One sandwich was described as a typical pork sandwich, with a typical chance of being contaminated with the food-borne pathogen, Trichinella. The second sandwich was described as having been treated by irradiation to control Trichinella, guaranteeing that the pork would not cause trichinosis.

Participants were told that they had a typical pork sandwich and that an irradiated sandwich would be sold in a sealed bid auction. They were told they would have to consume either a typical pork sandwich or an irradiated one to complete the experiment and leave.

The auction had 10 rounds of bidding, each with equal probability of being binding.

Before the bidding began, participants received the same baseline information: a neutral description of the food irradiation process, the parasite Trichinella, the effects of irradiation on the parasite, and the odds of contracting trichinosis from the sandwich.

Halfway through the bidding, participants in the positive treatment groups received a favorable description of food irradiation based on information provided by the American Council on Science and Health.

Participants in the negative treatment groups received an unfavorable description of irradiation based on information from the advocacy group, Food and Water, Inc.

Participants in the other groups were provided simultaneously with both the favorable and the unfavorable descriptions of irradiation.

In the positive and negative treatment groups, the information had the anticipated result. The favorable description of food irradiation caused the bid for irradiated pork to increase in those groups and the unfavorable description caused the average bid to decrease in those groups.

"As expected, providing good news about the product increases its value and bad news decreases its value," Hayes said.

In the groups receiving both treatments, the bids decreased and continued to fall. By the end of the bidding, 63 percent had submitted bids of $0.00.

"In fact, the effect of providing negative information alone was not significantly different from that of providing both types simultaneously. This result is true even when we identified the source of the negative information as a consumer advocacy group, and simultaneously presented information about safety from a wide variety of scientific bodies," Hayes said.

"We show that negative information dominates positive," Hayes said. "This finding indicates enormous responsibilities for those who provide information about risk, those who write negative descriptions of new food technologies and those who report on these controversies."


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