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University of Iowa News Release


Oct. 12, 2009

Products aren't contagious, but UI research shows we act as if they are

Urban legend has it that Las Vegas casinos hire what are known as "coolers," professional mopes who ease up next to players on a hot streak in the hope that their bad luck rubs off and cools the table down, little black clouds who save the house money by raining on winning parades.

A new study by a University of Iowa business professor suggests people make choices in ways that show we think such a thing is actually possible, despite our reason telling us it isn't.

Dhananjay Nayakankuppam, a professor of marketing in the Tippie College of Business, studies what is known as the contagion effect, an irrational belief that the qualities of something can somehow rub off on a nearby object. For instance, if a coffee mug is broken, the contagion effect tells us that this negative aspect rubs off on other coffee mugs nearby. This, despite the fact that we know broken coffee mugs are not contagious, or that people with bad attitudes don't lead to the turn of an unfriendly card at the blackjack table.

In a study published recently, Nayakankuppam found that the contagion effect also applies to whole groups surrounding the supposedly contagious item; the more contagious the groups were perceived to be, the more easily properties were perceived to spread across the entire group. In one experiment, Nayakankuppam and his co-researchers showed subjects two tables holding nine coffee mugs each wrapped in boxes and told that one of the boxes contained a mug with a gift coupon. On one of the tables, the boxes were placed close together, while on the other, they were spaced several inches apart. Participants could choose which table they would like to pick a mug from.

"There was a one in 9 chance-an objective probability-of selecting a mug with a gift coupon no matter which table participants chose, so the grouping ought to have had no influence on the preference," said Nayakankuppam. Yet, he said that the test subjects consistently selected a mug from the table where the boxes were arranged close together.

At the same time, another group of subjects were shown two tables of similarly arranged coffee mugs and told one mug was defective and might need to be repaired. This time, the subjects consistently selected from the table where the mugs were spaced further apart. 

Nayakankuppam said the results demonstrate that if one object in the group has a gain associated with it, such as a gift coupon, then the gain is perceived to spread through the group of products and all objects in that group will be seen as being infused with the gain. He said people who select from that group feel as if they are increasing their chances of selecting the positive item.

On the other hand, he said loss is also perceived to spread across a contagious group, reducing peoples' willingness to select an object from that group.

"The groups of closely arranged products seem more contagious than groups of more widely spaced products, and that proximity seems to facilitate the spread of both gain and loss," Nayakankuppam said. "So even though we understand rationally that there is no earthly way something could have been contaminated, we still act as if we believe it did."

The practical implications of Nayakankuppam's research could influence how stores display products. It also suggests ways to enhance or inhibit certain behaviors. For instance, "if a restaurant menu lists a tasty food such as ice cream near a group of healthful foods, the quality of tastiness is likely to spread across the whole group."

Nayakankuppam's paper, "The Group-Contagion Effect: The Influence of Spatial Groupings on Perceived Contagion and Preferences," was co-authored by Arul Mishra and Himanshu Mishra, UI doctoral alumni now teaching at the University of Utah. It was published in the journal Psychological Science.

STORY SOURCE: University of Iowa News Service, 300 Plaza Centre One, Iowa City, Iowa 52242-2500.

MEDIA CONTACT: Tom Snee, 319-384-0010 (office), 319-541-8434 (cell),; Dhananjay "D.J." Nayakankuppam, 319-335-1981,