최근 사회적 행동과 2D:4D 비율(둘째와 넷째 손가락 길이 비율, second-to-fourth digit ratio)과의 관계에 대한 관심이 높아지고 있다. 그 이유는 2D:4D 비율을 이용하여 사회적 행동의 개인차에 대한 생물학적 근거 즉, 태내 테스토스테론의 효과를 살펴볼 수 있기 때문이다. 태내 테스토스테론은 초기 뇌 발달과 손가락 길이 패턴에 관여할 뿐만 아니라, 출생 후 행동에 결정적 영향을 미친다. 2D:4D 비율이 낮을수록 상대적으로 높은 태내 테스토스테론에 노출되었다는 것을 나타낸다. 만약 태내 테스토스테론이 초기 뇌 발달, 손가락 비율, 그리고 출생 후 행동에 주요한 역할을 한다면, 다양한 종류의 사회적 행동은 2D:4D 비율과 관계가 있을 가능성이 높다. 또한 테스토스테론이 사회적 행동의 기저가 되는 신경구조와 기능의 조직화에 관여한다면, 이들 신경네트워크는 테스토스테론 의존 행동을 유발하는 특정 자극(예, 사회적 위협, 테스토스테론 처방)에 의해 활성화될 수 있어야 되며, 그리고 그 자극에 반응하여 나타나는 사회적 행동이 2D:4D 비율에 따라 다르게 나타나야 한다. 따라서 본 논문은 특정 자극에 반응하여 행동을 다르게 조절하는 2D:4D의 역할에 중점을 두고, 경제 게임(예, 신뢰 게임, 공공재 게임, 최후통첩 게임 등)을 이용하여 2D:4D와 사회적 행동(예, 사회적 협력, 위험 감수, 충동성, 그리고 공격성)과의 관련성에 대해 알아본 연구들을 살펴보았다. 또한 2D:4D, 순환 테스토스테론, 그리고 사회적 행동과의 관계에 대한 최근 연구들을 살펴보았다. 연구들은 사회적 의사결정이 2D:4D 비율에 따라 다르게 나타난다는 것을 보여주었다. 뿐만 아니라 태내 테스토스테론은 여러 사회적 행동의 기저가 되는 신경 메커니즘을 사전 프로그램하고, 생리적 또는 환경적 단서에 대한 반응으로 나타나는 행동을 촉진하거나 억제하기위해 신경과정을 선택적으로 조절하는 것으로 보인다.
Recently, there has been an increased interest in the relationship between 2D:4D ratio (second-to-fourth digit ratio) and social behaviors. It is because 2D:4D can be used to explore a potential biological basis (the effect of prenatal testosterone) of individual differences in social behavior. Prenatal testosterone has organizational effects on brain development and finger length pattern, as well as permanent influence on behavior in later life. Low 2D:4D indicates high level of testosterone relative to estrogen in utero. If prenatal testosterone plays an important role in early brain development, digit ratio and later behavior, social behavior should be related to 2D:4D. In addition, if prenatal testosterone shapes the neural networks underlying social behaviors, these networks may be able to be activated by specific stimuli (e.g., social threat, testosterone administration) that provoke testosterone-dependent behaviors, and social behaviors expressed in response to those stimuli may be modulated by 2D:4D. Therefore, this review outlines research findings of the relationship between 2D:4D and social behaviors (e.g., social cooperation, risk taking, impulsivity, and aggression) using economic games (e.g., Trust game, Public goods game, Ultimatum game, etc) with a main focus on the role of 2D:4D dynamics in modulating social behaviors in response to certain stimuli. Studies have shown that 2D:4D affects on social decision making. Furthermore, prenatal testosterone may preprogram the neural mechanisms underlying social behaviors, and it may selectively modifies neural processing to facilitate or inhibit social behaviors in response to environmental or physiological cues.
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