Annett M
Ann Hum Biol. 1976 Jul;3(4):317-28. doi: 10.1080/03014467600001541.
Hand preferences vary not discretely but continuously and the continuum of preference is closely and reliably linked with a continuous roughly Normal distribution of differences between the hands in skill. Questions about handedness can be usefully formulated in terms of the distribution of differences in skill and in terms of the theshold or criterion which divided those likely to be classified as right handers from those likely to be classified as left handers. A theory of the origin of hand preferences suggests that three factors are involved. The first in non-genetic accidental variation in the development of the two sides of the body in all bilaterally symmetrical species showing limb preferences. The second in a systematic bias to the right hand in man, probably linked with the tendency for the left hemisphere to serve speech. The third is socio-cultural factors affecting the expression of sinistrality. An explanation of the relation between hand preference and cerebral speech laterality requires the assumption that in some individuals the factor biasing speech to the left hemisphere is absent. This would imply that the bias is not a universal species character but that it is subject to genetic variation. Making the simplest possible further assumptions that in the absence of bias, the laterality of handedness and of cerebral speech are independent and each governed by chance, it is possible to account for the distribution of right and left handers with dysphasias following right and left unilateral cerebral lesions.
用手偏好并非离散变化而是连续变化的，并且这种偏好的连续统与双手在技能方面的差异的连续且大致呈正态分布紧密且可靠地相关联。关于用手习惯的问题可以根据技能差异的分布以及区分可能被归类为右利手和左利手的阈值或标准来有效提出。一种关于用手偏好起源的理论表明涉及三个因素。第一个因素是在所有表现出肢体偏好的双侧对称物种中，身体两侧发育过程中的非遗传偶然变异。第二个因素是人类中对右手的系统性偏向，这可能与左半球负责语言功能的倾向有关。第三个因素是影响左利手表达的社会文化因素。对用手偏好与大脑语言偏侧性之间关系的一种解释需要假设在一些个体中不存在使语言偏向左半球的因素。这意味着这种偏向并非普遍的物种特征，而是受基因变异影响。做出尽可能简单的进一步假设，即在没有偏向的情况下，用手习惯的偏侧性和大脑语言的偏侧性是独立的，且各自由随机因素决定，那么就有可能解释在右侧和左侧单侧脑损伤后出现失语症的右利手和左利手的分布情况。
