The mirror self-recognition test evaluates whether a subject touches a mark on its own body that is visible only in a mirror, and is widely used as an indicator of self-awareness. In this study, we present a computational model in which this behavior emerges spontaneously through a single mechanism, the self-prior, without any external reward. The self-prior, implemented with a Transformer, learns the density of familiar multisensory experiences; when a novel mark appears, the discrepancy from this learned distribution drives mark-directed behavior through active inference. A simulated infant, relying solely on vision and proprioception without tactile input, discovered a sticker placed on its own face in the mirror and removed it in approximately 70% of cases without any explicit instruction. Expected free energy decreased significantly after sticker removal, confirming that the self-prior operates as an internal criterion for distinguishing self from non-self. Cross-modal sampling further demonstrated that the self-prior captures visual--proprioceptive associations, functioning as a probabilistic body schema. These results provide a concise computational account of the key behavior observed in the mirror test and suggest that the free energy principle can serve as a unifying hypothesis for investigating the developmental origins of self-awareness. Code is available at: https://github.com/kim135797531/self-prior-mirror

翻译：镜像自我识别测试通过评估受试者是否能触摸仅通过镜子可见的自身身体标记，被广泛用作自我意识的指标。本研究提出一个计算模型，其中该行为通过单一机制——自先验（self-prior）自发涌现，无需任何外部奖励。自先验通过Transformer实现，学习熟悉多感官体验的密度分布；当出现新颖标记时，该学习分布与当前体验的差异通过主动推断驱动指向标记的行为。一个仅依赖视觉和本体感觉（无触觉输入）的模拟婴儿，在无任何明确指令的情况下，约70%的案例中发现并移除贴在自己脸上（通过镜子可见）的贴纸。贴纸移除后预期自由能显著下降，证实自先验可作为区分自我与非自我的内部准则。跨模态采样进一步证明，自先验捕获了视觉-本体感觉关联，发挥概率身体图式的作用。这些结果为镜像测试中观察到的关键行为提供了简洁的计算解释，并表明自由能原理可作为探究自我意识发展起源的统一假说。代码地址：https://github.com/kim135797531/self-prior-mirror