The study has shed light on why, at a casino, people seem to gather around machines and people on a winning streak.

"It is common to find that people consider luck to be contagious-they are likely to believe that being near a person on a winning streak somehow enhances their own chances of winning," said author Arul Mishra (University of Utah, Salt Lake City).

His study focused on testing whether consumers would make product choices based on the same contagion principle.

Participants in one of his studies were asked to choose a Pepsi bottle from one of two groups.

In one group the bottles were close together and in the other they had been arranged apart.

When the consumers were told that one of the bottles in each group contained a gift coupon, the majority of subjects chose a bottle from the close-together group.

However, when participants were told that one of the bottles in each group was defective, they were more likely to choose from the group with the bottles arranged apart.

Mishra said that the research showed that "the age-old belief that qualities are contagious and transferable is quite pervasive in simple everyday decisions."

He determined that a group that is considered contagious appears to spread the qualities of one of its members to the complete group.

So, for gain, the contagious (close) group appears more attractive since the whole group seems to reflect the positive quality.

However, for loss, a non-contagious group appears more attractive since in such a group the loss quality appears to spread less.

"Despite the fact that the qualities (a gift coupon or a product defect) cannot physically spread from one object to the other, people still believe in the contagiousness of qualities based on their grouping," said Mishra.

The research has implications for product choice, persuasiveness of advertising messages, and retail shelf displays.