Observational research on the social impact of cell phone usage in public places suggests that the mere presence of cell phones in public conflicts the private and public spheres and inhibits social interaction with proximate others (strangers or known persons). The purpose of this paper is to develop a theoretical model for which social effects of cell phone usage in public places documented in observational studies can be empirically tested. In this paper, we discuss various variables to consider in the study of cell phone usage (CPU) and social interaction with proximate others (SIPO). We offer a modest experiment of CPU in the context of social participation, a form of social interaction. Focusing on helping behavior in particular, results indicate that while on the cell phone, users are less likely to offer help. Findings imply that CPU in public places can distract users from social responsibilities, as they neglect the environment surrounding them.