People punish generous group members by rejecting them socially -- even when the generosity benefits everyone -- because the "big givers" are nonconformists, according to a Baylor University study.

The study, published in the journal Social Science Research, showed that besides socially rejecting especially generous givers, others even "paid" to punish them through a points system.

"This is puzzling behavior," said researcher Kyle Irwin, Ph.D., an assistant professor of sociology in Baylor's College of Arts & Sciences. "Why would you punish the people who are doing the most -- especially when it benefits the group? It doesn't seem to make sense on the surface, but it shows the power of norms. It may be that group members think it's more important to conform than for the group to do well."

"Free-riders" - those who were stingy but benefited from others' larger contributions -- also were nonconformists and ostracized.

Irwin and co-researcher Christine Horne, Ph.D., a sociologist at Washington State University, conducted a "public goods" experiment with 310 participants. Each person was given 100 points (which translated into opportunities to win a gift card) and had to decide how many to give to the group and how many to keep. Contributions were doubled and divided equally regardless of how much people donated. Decisions were made via computers, and individuals did not know or communicate with other group members before making their decisions. (In the experiment, other group members actually were simulated, with pre-programmed behavior.)

Each participant was told that he or she would see the amounts of four others and be the fifth giver, with a sixth person ending the sequence. The final giver always was pre-programmed to be stingier or much more generous than the others.

Each group member had the opportunity to "pay" via the points system to punish those who contributed the most. The "punisher" would have to give up one point for every three points he or she deducted from the most generous member.

Each member also rated on a scale of 1 to 9 how much they wanted each of the others to remain in the group.

Group members' donations averaged 50 percent of their resources. The "stingiest" individual gave only 10 percent, while the most generous one gave 90 percent.

Irwin likened the punishments to shunning or poking fun at someone who had done the bulk of work in a group project for a class -- or even kicking the person out of the group.

"There could be a number of reasons why the others punish a generous member," he said. "It may be that the generous giver made them look or feel bad. Or they may feel jealous or like they're not doing enough."

Irwin suggested that at some point, if the contributions became very large, group members' wish to benefit might override their desire to punish.