This research aims to understand how a dynamic social context affects consumer decisions. Currently, research in this area is focused mainly on factors that affect individual decision processes without a social context. The findings will shed light on consumer purchase decisions and satisfaction, and help marketers better understand consumer behaviour. I examine in a number of projects how the presence or anticipation of social presence affects consumer behaviours. These include how people make gift-giving choices, surrogate decisions for others, reciprocation decisions (e.g., how people initiate and repay favours), as well as prosocial decisions (e.g., donations and volunteering).