“左撇子”有时是遗传缺陷的表达或是早期的发育迟缓。在这一期的Deutsches Ärzteblatt International上，Stefan Gutwinski与合著者对左撇子和右撇子提出当前的科学理解。
在所有族群中都能发现左撇子。它出现在人类进化过程中的早期，在更高认知功能的发展中起关键作用。例如，人类语言被认为是与通过手势的手动交流的单侧大脑控制的发展一起出现的。而且，它就在左右手习惯形成后出现，其中左右手习惯是所能发展的人类手的非常精细的运动功能。
大部分时间里，左撇子只是自然出现，正常变异。但是，在一些病例中，它是一种不便，可能正好反映出遗传缺陷或早期发育障碍。然而，左撇子和右撇子在患特定疾病的人中似乎更常见。
例如，在癫痫、精粹分裂症和孤独症中可观察到这种现象。而且，当前研究显示，相对于右大脑半球而言，左大脑半球活动减少可能导致抑郁和躁狂症的相对失调。（生物谷bioon.com)
doi:10.3238/arztebl.2011.0849
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Understanding Left-Handedness
Gutwinski, S; Löscher, A; Mahler, L; Kalbitzer, J; Heinz, A; Bermpohl, F
Background: The human cerebrum is asymmetrical, consisting of two hemispheres with differing functions. Recent epidemiological and neurobiological research has shed new light on the development of the cerebral lateralization of motor processes, including handedness. In this article, we present these findings from a medical perspective. Method: We selectively searched the PubMed online database for articles including the terms "handedness," "left handedness," "right handedness," and "cerebral lateralization." Highly ranked and commonly cited articles were included in our analysis. Results: The emergence of handedness has been explained by physiological and pathological models. Handedness arose early in evolution and has probably been constitutive for the development of higher cognitive functions. For instance, handedness may have provided the basis for the development of speech and fine motor skills, both of which have played a critical role in the evolution of mankind. The disadvantages of certain types of handedness are discussed, as some cases seem to be associated with disease. Conclusion: The consideration of handedness from the epidemiological, neurobiological, and medical points of view provides insight into cerebral lateralization.
