Data from: Variant at serotonin transporter gene predicts increased imitation in toddlers: relevance to the human capacity for cumulative culture

Cumulative culture ostensibly arises from a set of sociocognitive processes which includes high-fidelity production imitation, prosociality and group identification. The latter processes are facilitated by unconscious imitation or social mimicry. The proximate mechanisms of individual variation in imitation may thus shed light on the evolutionary history of the human capacity for cumulative culture. In humans, a genetic component to variation in the propensity for imitation is likely. A functional length polymorphism in the serotonin transporter gene, the short allele at 5HTTLPR, is associated with heightened responsiveness to the social environment as well as anatomical and activational differences in the brain's imitation circuity. Here, we evaluate whether this polymorphism contributes to variation in production imitation and social mimicry. Toddlers with the short allele at 5HTTLPR exhibit increased social mimicry and increased fidelity of demonstrated novel object manipulations. Thus, the short allele is associated with two forms of imitation that may underlie the human capacity for cumulative culture. The short allele spread relatively recently, possibly due to selection, and its frequency varies dramatically on a global scale. Diverse observations can be unified via conceptualization of 5HTTLPR as influencing the propensity to experience others' emotions, actions and sensations, potentially through the mirror mechanism.

累积文化（Cumulative culture）表面上源于一系列社会认知过程，涵盖高保真动作模仿（high-fidelity production imitation）、亲社会性（prosociality）与群体认同（group identification）。此类后续过程可通过无意识模仿（unconscious imitation）或社会模仿（social mimicry）得到促进。因此，个体模仿差异的近因机制（proximate mechanisms）或可揭示人类累积文化能力的进化历程。在人类中，模仿倾向（propensity for imitation）的差异存在遗传基础的可能性较高。血清素转运体基因（serotonin transporter gene）中存在一处功能性长度多态性（functional length polymorphism）——即5HTTLPR位点的短等位基因（short allele），该多态性与个体对社会环境的增强敏感性，以及大脑模仿神经回路的解剖学特征与激活模式差异均存在关联。本研究旨在探究该多态性是否会对动作模仿与社会模仿的个体差异产生影响。携带5HTTLPR短等位基因的幼儿，其社会模仿行为更为显著，且对演示的新型物体操作动作的模仿保真度更高。由此可见，该短等位基因与两种模仿形式存在关联，而这两种模仿形式或正是人类累积文化能力的基础。该短等位基因的传播时间相对较近，其传播可能受到自然选择的推动，且其在全球范围内的等位基因频率存在显著差异。若将5HTTLPR的功能概念化为通过镜像机制（mirror mechanism）影响个体对他人情绪、行为与感受的感知倾向，则可统一解释各类观测结果。