My Neighbor Next Floor: The Built Environment and Social Preferences
利用上海因快速开发而随机分配到不同楼层的家庭，通过自然田野实验（误投邮件）发现，仅相隔一层楼就会使帮助邻居的意愿降低16个百分点，表明空间距离对城市中的亲社会行为有显著影响。
Abstract We assess the effect of the built environment on low-cost helping behavior toward neighbors. The setting is households in Shanghai, China that, due to rapid development, were involuntarily, i.e. as good as randomly, relocated to different building structures. Using a natural field experiment of misdelivered mail, we test the causal effect of spatial proximity and the built environment on helping behavior. Living one floor apart reduces the willingness to help a neighbor by 16 percentage points, similar to adding one more apartment per floor. Small spatial barriers can profoundly shape social interactions, and helping behavior, in urban settings.