The fusion of personal and group identities can lead to self-sacrificial progroup behavior, from acts of charity to violent extremism. Two pathways to identity fusion—via shared biology and shared experiences—have been proposed. In this article, we elucidate a new developmental account of the origins and mechanisms of these two pathways to identity fusion from childhood to adulthood. Whereas fusion based on shared biology occurs from early childhood cued by phenotypic similarity, fusion based on episodic memories of shared experiences is not possible until midadolescence and relies on suitable bonding experiences (e.g., painful initiation rituals, emotionally intense team sports). The critical development that enables fusion based on shared experiences is autobiographical reasoning, which entails connecting one’s past experiences to the present self. Autobiographical reasoning begins in adolescence, which may explain the flourishing of fusion in late adolescence and young adulthood relative to other life periods. Fusion via either pathway is linked to strong progroup behavior. We outline a program of empirical research on the development of identity fusion while addressing relevant methodological challenges. A developmental framework may help foster efforts to harness identity fusion for peaceful rather than violent forms of self-sacrifice for the group.

个人和群体身份的融合可能导致自我牺牲的亲群体行为，从慈善行为到暴力极端主义。已经提出了两种身份融合途径——通过共享生物学和共享经验。在本文中，我们阐明了从童年到成年这两种身份融合途径的起源和机制的新发展解释。虽然基于共享生物学的融合发生在由表型相似性暗示的儿童早期，但基于共享经历的情景记忆的融合直到青春期才可能实现，并且依赖于适当的结合体验（例如，痛苦的入会仪式，情绪激烈的团队运动）。基于共享经验实现融合的关键发展是自传推理，这需要将一个人过去的经历与现在的自我联系起来。自传体推理始于青春期，这可能解释了青春期后期和青年期相对于其他生命时期融合的蓬勃发展。通过任一途径的融合与强前群行为有关。我们概述了一个关于身份融合发展的实证研究计划，同时解决相关的方法学挑战。一个发展框架可能有助于促进利用身份融合为群体进行和平而不是暴力形式的自我牺牲。我们概述了一个关于身份融合发展的实证研究计划，同时解决相关的方法学挑战。一个发展框架可能有助于促进利用身份融合为群体进行和平而不是暴力形式的自我牺牲。我们概述了一个关于身份融合发展的实证研究计划，同时解决相关的方法学挑战。一个发展框架可能有助于促进利用身份融合为群体进行和平而不是暴力形式的自我牺牲。