ABSTRACT

Until fairly late in the nineteenth century, it was held that the brain was bilaterally symmetrical. With the discovery of left-brain dominance for language, the so-called “laws of symmetry” were revoked, and asymmetry was then seen as critical to the human condition, with the left hemisphere, in particular, assuming superordinate properties. I trace this idea from the early discoveries of the late nineteenth century through the split-brain studies of the 1960s, and beyond. Although the idea has persisted, the evidence has revealed widespread cerebral asymmetries in nonhuman animals, and even language and its asymmetries are increasingly understood to have evolved gradually, rather than in a single speciation event. The left hemisphere nevertheless seemed to take over a role previously taken by other structures, such as the pineal gland and the hippocampus minor, in a determined effort to place humans on a pedestal above all other species.

摘要

直到十九世纪后期，人们才认为大脑是左右对称的。随着语言左脑优势的发现，所谓的“对称律”被废除，不对称被视为对人类状况的关键，尤其是左半球具有上乘特性。我从19世纪后期的早期发现到1960年代及以后的裂脑研究追溯了这个想法。尽管这一想法一直存在，但证据表明，非人类动物普遍存在大脑不对称现象，甚至越来越多的语言及其不对称现象被理解为是逐渐演变的，而不是一次物种形成事件。不过，左半球似乎取代了以前由其他机构承担的角色，