Adolescent social isolation induces persistent impairments in emotional discrimination and helping behavior

Prosocial behaviors, helpful actions directed toward the well-being of others, are an essential component of social behavior. Adolescence is a particularly sensitive period for the development of social behaviors, yet how social experience during this window shapes prosocial behavior remains poorly understood. Here, we used behavioral assays to examine how social isolation at different ages affects emotional discrimination and affiliative helping behavior in mice of both sexes. We found that adult mice raised in social isolation since weaning failed to allogroom distressed conspecifics and were unable to distinguish stressed from unstressed mice in an emotional discrimination assay. Remarkably, two weeks of post-weaning social isolation was already sufficient to impair both emotional discrimination and prosocial allogrooming, and these deficits persisted despite two months of resocialization. In contrast, two weeks of adult social isolation spared emotional discrimination but impaired allogrooming toward stressed conspecifics. These findings reveal a dissociation between emotional discrimination and prosocial helping behavior. Overall, this work identifies adolescence as a sensitive period for the development of emotional state recognition and provides a behavioral framework for investigating how early social experience sculpts neural circuits underlying empathy and stress-buffering. Significance Statement Prosocial behaviors are essential for social cohesion and emotional well-being in social animals, but what shapes their development remains poorly understood. We show that social isolation during adolescence impairs the mouse’s ability to recognize the emotional state of stressed conspecifics, which cannot be rescued by subsequent resocialization. In contrast, social isolation in adulthood impairs prosocial actions without disrupting emotional discrimination. These findings identify adolescence as a critical period for the development of socio-affective behavior, and reveal a dissociation between emotional discrimination and prosocial helping behavior. Our study provides a behavioral framework for investigating how early social experience sculpts neural circuits underlying empathy and stress-buffering and establishes a foundation for mechanistic studies of adolescent vulnerability to social and affective disorders.