Social influence is a strong determinant of food consumption, which in turn influences health. Although consistent observations have been made on the role of social factors in driving similarities in food consumption, much less is known about the precise governing mechanisms. We study social influence on food choice through carefully designed causal analyses, leveraging the sequential nature of shop queues on a major university campus. In particular, we consider a large number of adjacent purchases where a focal user immediately follows another user ("partner") in the checkout queue and both make a purchase. Identifying the partner's impact on the focal user, we find strong evidence of a specific behavioral mechanism for how dietary similarities between individuals arise: purchasing mimicry, a phenomenon where the focal user copies the partner's purchases. For instance, across food additions purchased during lunchtime together with a meal, we find that the focal user is significantly more likely to purchase the food item when the partner buys the item, v.s. when the partner does not, increasing the purchasing probability by 14% in absolute terms, or by 83% in relative terms. The effect is observed across all food types, but largest for condiments, and smallest for soft drinks. We find that no such effect is observed when a focal user is compared to a random (rather than directly preceding) partner. Furthermore, purchasing mimicry is present across age, gender, and status subpopulations, but strongest for students and the youngest persons. Finally, we find a dose-response relationship whereby mimicry decreases as proximity in the purchasing queue decreases. The results of this study elucidate the behavioral mechanism of purchasing mimicry and have further implications for understanding and improving dietary behaviors on campus.

翻译：社会影响是食物消费的重要决定因素，进而影响健康。尽管社会因素在推动食物消费相似性方面的作用已有持续观察，但其精确的作用机制仍知之甚少。本研究通过精心设计的因果分析，利用某大型大学校园中商店队列的顺序性质，研究社会因素对食物选择的影响。具体而言，我们考察了大量相邻购买行为，其中一位焦点用户在结账队列中紧随另一位用户（"伙伴"）之后，且两者均进行了购买。通过识别伙伴对焦点用户的影响，我们发现了个体间饮食相似性产生的特定行为机制的有力证据：购买模仿——焦点用户模仿伙伴购买行为的现象。例如，在午餐时间与主食一起购买的加购食品中，我们发现当伙伴购买该食品时，焦点用户购买该食品的概率显著高于伙伴不购买时的概率，绝对概率增加14%，相对概率增加83%。这种效应在所有食品类型中均被观察到，其中调味品效应最大，软饮料效应最小。我们发现，当焦点用户与随机（而非直接前序）的伙伴进行比较时，未观察到此类效应。此外，购买模仿现象存在于不同年龄、性别和身份子群体中，但在学生和最年轻群体中表现最强。最后，我们发现了剂量-反应关系，即购买队列中邻近程度降低时，模仿效应也随之减弱。本研究结果阐明了购买模仿的行为机制，并对理解和改善校园饮食行为具有进一步启示意义。