Consumers who buy products that give a portion of their sales to charities -- think Yoplait and Susan G. Komen for the Cure -- are less likely to give direct donations to that same charity, a new study finds.

Not only that, consumers' feelings of altruism decline when they wind up with a product such as a stuffed animal or T-shirt in addition to their donation, the study found.

The research, from the University of Michigan Ross School of Business, stirs up debate over the ever-growing world of cause marketing. The strategy ranges from the long-standing General Mills "Box Tops for Education" to Pepsi Refresh, a campaign that allows people to vote online for their favorite charitable causes.

"Consumers appear to realize that participating in cause marketing is inherently more selfish than direct charitable donation, reducing their subsequent happiness," said Aradhna Krishna, the marketing professor who conducted the study, in a university press release.

"Unfortunately, this doesn't prevent them from substituting it for charitable giving, which reduces the overall charitable donation."

Krishna based her conclusions on several studies involving about 300 college students. She found that if two people had the same preference for a charitable product, and one of them bought that product, the person who didn't buy the product would donate more money directly to the cause.

The more money they spent on the charitable product, the less money they would donate directly to the charity, the study showed.

The research offers a glimpse into the down side of cause marketing, which previous studies have touted for its ability to attract consumers and employee loyalty. Cause marketing can increase sales, studies have shown, but it can also increase the cost of the product. And the portion of money going to charity varies widely.

The study is slated to be published in the July issue of the Journal of Consumer Psychology.

Jean Hopfensperger • 612-673-4511