Research Department of Clinical, Educational and Health Psychology, University College London, London, UK.
Laterality. 2021 May;26(3):310-314. doi: 10.1080/1357650X.2021.1892126. Epub 2021 Mar 2.
Non-shared environmental variance (NSEV) accounts for 76% of variance in genetic modelling of handedness. However, it is very misleading to suggest that NSEV, "highlights the importance of non-genetic factors for the ontogenesis of hemispheric asymmetries". NSEV is poorly named, is calculated only by subtraction, and provides no direct evidence for environmental effects in the sense of the external environment. Miller suggested that it would be better named as "residual effect". Mitchell has suggested that much or indeed most of NSEV is "developmental variance" and should be included under the heading of nature rather than nurture, and in handedness, "largely reflect[s] the outcome of randomness in brain development". Overall only a very small proportion of NSEV in handedness is likely to be related to external environmental factors in the usual sense of the term.
非共享环境方差（NSEV）占-handedness 遗传建模方差的 76%。然而，说 NSEV“强调了非遗传因素对半球不对称性的发生的重要性”是非常误导人的。NSEV 命名不当，仅通过减法计算，并且不能直接证明外部环境的环境影响。Miller 建议将其更好地命名为“剩余效应”。Mitchell 认为，NSEV 的大部分甚至全部都是“发育方差”，应该归入自然而不是教养的范畴，在-handedness 中，“主要反映了大脑发育中的随机性结果”。总体而言，-handedness 中 NSEV 的很小一部分可能与通常意义上的外部环境因素有关。
