Actions speak louder than words: An elaborated theoretical model of the social functions of self-injury and other harmful behaviors.

The question of why some people do things that are intentionally harmful to themselves continues to puzzle scientists, clinicians, and the public. Prior studies have demonstrated that one fairly extreme, direct form of self-harm, non-suicidal self-injury (NSSI), is maintained by both automatic (i.e., intrapersonal) as well as social (i.e., interpersonal) reinforcement. However, the majority of theoretical and empirical papers on this topic focus almost exclusively on the automatic functions. The purpose of this paper is to provide a more comprehensive analysis of the social functions of NSSI. Evidence is presented supporting the notion that NSSI is maintained by social reinforcement in at least a substantial minority of instances. Moreover, an elaborated theoretical model of the social functions of NSSI is outlined that proposes that this behavior represents a high intensity social signal used when less intense communication strategies fail (e.g., speaking, yelling, crying). The model further proposes that NSSI can serve not only as a signal of distress that is reinforced primarily by the caregiving behavior it elicits from others, but that it also can serve as a signal of strength and fitness that is reinforced by warding off potential threats (e.g., peer victimization), and in some cases can strengthen affiliation with others. Support for this theoretical model is drawn from diverse literatures including psychology, evolutionary biology, and cultural anthropology. The paper concludes with specific recommendations for empirical tests of the proposed model of the social functions of NSSI, as well as other harmful behaviors such as alcohol and drug use.