We may automatically comply with a request when we have been given or promised something of value. The gift may be a material item, or advice, or help. When someone has done something for you, you feel an inclination to reciprocate. This strong tendency to reciprocate exists even in situations where the person receiving the gift hasn't asked for it. One of the most effective ways to influence people to do us a "favor" (comply with a request) is by giving some gift or assistance that forms an underlying obligation.