"People will choose more variety for others than for themselves, and this tendency [is] even larger when they have to justify their choices," explain Incheol Choi and Youjae Yi (Seoul National University).
The subjects in the study were shown nine different snacks and asked to select a total of five snacks for their partner to receive at the end of the study. They could choose any combination, such as five of the same snack, five different snacks, or any other combination. One group of subjects was asked to write down their reasons for choosing particular snacks, while the other group was not asked to justify their selections. Those held accountable for their choices selected a higher variety of snacks for their partners.
The authors believe that this tendency is due to two factors: a desire to conform to a "[social] norm advocating variety for others," and a tendency "to focus on the consumptions per se without considering other activities those others would engage [in] during the inter-consumption period," they explain.
In other words, subjects appear to forget that the person for whom they're choosing snacks won't eat them all at once. More likely, the person will have one or two now, do other activities, and then have another later. Choi and Yi also show that we expect someone else's satisfaction after eating the same snack five days in a row to be lower than our own would be.
However, when the researchers had subjects list the daily activities their partner might do on the five days for which they were choosing snacks, this "de-focusing" task caused a significant reduction in the variety of snacks chosen.
Jinhee Choi, B. Kyu Kim, Incheol Choi, and Youjae Yi. "Variety-Seeking Tendency in Choice for Others: Interpersonal and Intrapersonal Causes." Journal of Consumer Research, March 2006.
Journal of Consumer Research