Immaterial and monetary gifts in economic transactions: evidence from the field
通过购买快餐和午餐的田野实验，研究发现员工收到赞美等非物质礼物后，会以更高的产品重量回报，且这种互惠行为随时间增强；而金钱小费虽有更强初始效应，但不会随时间变化。
Abstract Reciprocation of monetary gifts is well-understood in economics. In contrast, there is little research on reciprocal behavior following immaterial gifts like compliments. We narrow this gap and investigate how employees reciprocate after receiving immaterial gifts and material gifts over time. We purchase (1) ice cream from fast food restaurants, and (2) durum doner, a common lunch snack, from independent vendors. Prior to the food’s preparation, we either compliment or tip the salesperson. We find that salespersons reciprocate compliments with higher product weight than in a control treatment. Importantly, this reciprocal behavior following immaterial gifts grows over repeated transactions. Tips, in contrast, have a stronger level effect which does not change over time.