ABSTRACT
In the first chapter, Schumann attempts to give a neurobiological explanation for variation in human mental and physical abilities and for variation in aptitude for second language learning. He argues that all brains are substantially different at the level of microanatomy and physiology. These differences are selected on by the environment and produce vast differences in aptitudes and abilities across human individuals. The goal of this book, as a whole, is to argue that no special mechanisms are required for second language learning, but nevertheless some learners have brains that are so constructed as to give them special talent for acquiring a second language even well after the beneficial effects of a critical or sensitive period would have ceased. This variation in aptitude and the variation in motivation described in the second chapter provide a neurobiological theory for individual differences in second language acquisition and learning in general.
