"(Prior theories of altruism)...Instead, it is likely that two other factors drive helping. The first is positive reputation. Most of us would not survive a week alone in the woods. We count on the cooperation of others, who we assume will provide us with everything from protection to food, so long as we pitch in. Behaving altruistically is a sure-fire sign that we have pitched in, and shows others that we are the type of person they should trust and help. In such a system, a good reputation is the most important currency we have, and there is evidence that people value that currency, acting altruistically more often in public than in private. Charities build on this value, publicizing donations and even providing reputation-boosting tokens like NPR bumper stickers and Livestrong bracelets..." - Lit

"If desiring a good reputation was the only psychological source of altruism, we may be tempted to agree that helping is impure. However, there is probably a more basic source powering altruism, one so ingrained that we could call it an "altruism instinct." Evidence for this comes from infants who act altruistically even though they likely don't understand the ins and outs of reputation building...." - Lit