Typically developing infants rapidly acquire a sophisticated array of social skills within the first year of life. These social skills are largely learned within the context of day-to-day interactions with caregivers. While social neuroscience has made great gains in our knowledge of the underlying neural circuitry of social cognition and behavior, much of this work has focused on experiments that sacrifice ecological validity for experimental control. Functional near-infrared spectroscopy (fNIRS) is a promising methodology for measuring brain activity in the context of naturalistic social interactions. Here, we review what we have learned from fNIRS studies that have used traditional experimental stimuli to study social development during infancy. We then discuss recent infant fNIRS studies that have utilized more naturalistic social stimuli, followed by a discussion of applications of this methodology to the study of atypical social development, with a focus on infants at risk for autism spectrum disorder. We end with recommendations for applying fNIRS to studies of typically developing and at-risk infants in naturalistic social situations.

通常，成长中的婴儿在出生后的第一年内会迅速掌握各种复杂的社交技能。这些社交技能主要是在与护理人员的日常互动中学习的。尽管社会神经科学在我们对社会认知和行为的潜在神经回路的了解方面取得了长足的进步，但这项工作大部分都集中在牺牲实验的生态有效性上进行实验的实验上。功能性近红外光谱法（fNIRS）是一种在自然主义社会互动中测量大脑活动的有前途的方法。在这里，我们回顾了从fNIRS研究中学到的东西，这些研究使用传统的实验刺激来研究婴儿期的社会发展。然后，我们将讨论最近的婴儿fNIRS研究，这些研究利用了更多自然主义的社会刺激，随后讨论了该方法在非典型社会发展研究中的应用，重点是处于自闭症谱系障碍风险中的婴儿。我们最后提出了建议，将fNIRS应用于自然社会环境中典型的发育中和处于危险中的婴儿的研究。