Bishop D V
Department of Experimental Psychology, University of Oxford.
Behav Genet. 2001 Jul;31(4):339-51. doi: 10.1023/a:1012239617367.
Data from two twin studies were used to address two related questions. First, is there any association between handedness and specific speech and language impairment (SSLI) in children? Second, is there genetic influence on individual differences in handedness and, if so, are the same genes implicated in the cause of SSLI? The first study used data from 58 MZ and 26 DZ pairs previously recruited for an investigation into the genetic origins of SSLI. All pairs contained at least one child with SSLI. Handedness was assessed using a preference inventory and a tapping task from which a laterality quotient (LQ) was derived. There were no handedness differences between these twins and 172 singleborn controls, and neither measure revealed any association between handedness and SSLI. The data were equally well-fitted by a CE model (no genetic influence) and an AE model (no effect of shared environment) for both hand preference and tapping LQ. Nonshared environment was the largest influence on handedness for both measures. Bivariate analysis indicated no overlapping genetic influences on SSLI and handedness. In the second study, handedness was assessed in a general population sample of 48 MZ and 44 DZ twin pairs, aged 7 to 13 years, using a preference inventory and a peg-moving task. A subset of children was also given a test that assessed persistence of hand preference when reaching across the midline. The latter was the only measure to relate to children's language status, with language-impaired children showing less midline crossing. This appears to reflect neurodevelopmental immaturity, rather than a stable trait. To investigate familial transmission of handedness, inventory data for parents and their twins were combined for both samples. The most parsimonious model was one that accounted for parent-child resemblance solely in terms of cultural transmission. Overall, there was no evidence that genes play a role in determining stable individual differences in hand preference. Insofar as there are links between handedness and speech and language difficulties, these reflect delayed neuromotor maturation.
两项双胞胎研究的数据被用于回答两个相关问题。第一，儿童的用手习惯与特定言语和语言障碍（SSLI）之间是否存在关联？第二，用手习惯的个体差异是否受遗传影响？如果是，导致SSLI的基因是否相同？第一项研究使用了先前为调查SSLI的遗传起源而招募的58对同卵双胞胎和26对异卵双胞胎的数据。所有双胞胎对中至少有一个孩子患有SSLI。使用偏好量表和敲击任务评估用手习惯，并由此得出利手商数（LQ）。这些双胞胎与172名单胎出生的对照组在利手方面没有差异，两种测量方法均未显示用手习惯与SSLI之间存在关联。对于利手偏好和敲击LQ，CE模型（无遗传影响）和AE模型（共享环境无影响）对数据的拟合效果同样良好。非共享环境对这两种测量方法的利手影响最大。双变量分析表明，SSLI和利手之间没有重叠的遗传影响。在第二项研究中，使用偏好量表和移 peg 任务对48对同卵双胞胎和44对异卵双胞胎（年龄在7至13岁之间）的普通人群样本进行了用手习惯评估。还对一部分儿童进行了一项测试，该测试评估了他们在越过中线伸手时手偏好的持续性。后者是唯一与儿童语言状况相关的测量方法，语言受损儿童越过中线的情况较少。这似乎反映了神经发育不成熟，而不是一种稳定的特征。为了研究用手习惯的家族传递，将两个样本中父母及其双胞胎的量表数据进行了合并。最简约的模型是一个仅从文化传递角度解释亲子相似性的模型。总体而言，没有证据表明基因在决定手偏好的稳定个体差异中起作用。就用手习惯与言语和语言困难之间存在联系而言，这些反映了神经运动发育延迟。
