“…The norm prescribes that one should help those who have helped him/her in the past and retaliate against those who have been detrimental to his/her interests. Reciprocity has been used in social psychology to explain a wide range of phenomena, such as attitude change (Cialdini, Green, & Rusch, 1992), intimacy in close relationships (Surra & Longstreth, 1990), interpersonal perception (Kenny, Bond, Mohr, & Horn, 1996), altruism (Krebs, 1975), aggression (Robarchek & Robarchek, 1998), cooperation (Komorita & Parks, 1999), intergroup interactions (Goren & Bornstein, 1999), consumer shopping (Miller & Kean, 1997), restaurant tipping (Rind & Strohmetz, 1999), and gift giving (Cialdini, 1988).…”