Where does grammar come from? How does it develop in children? Developmental psycholinguists who set out to answer these questions quickly find themselves impaled upon the horns of a dilemma, caught up in a modern variant of the ancient war between empiricists and nativists. Indeed, some of the fiercest battles in this war have been waged in the field of child language. Many reasonable individuals in this field have argued for a middle ground, but such a compromise has proven elusive thus far, in part because the middle ground is difficult to define. So let us begin with some definitions. The core of this debate is about epistemology, a branch of philosophy that we can define as “The study of knowledge, its form and source, and the process by which it comes to be. ” Within this framework, empiricism can be defined as “The belief that knowledge originates in the environment and comes into the mind/brain through the

The term “aphasia ” refers to acute or chronic impairment of language, an acquired condition that is most often associated with damage to the left side of the brain, usually due to trauma or stroke. We have known about the link between left-hemisphere damage and language loss for more than a century (Goodglass, 1993). For almost as long, we have also known that the lesion/symptom correlations observed in adults do not appear to hold for very young children (Basser, 1962; Lenneberg, 1967). In fact, in the absence of other complications, infants with congenital damage to one side of the brain (left or right) usually go on to acquire language abilities that are well within the normal range (Eisele & Aram, 1995; Feldman, Holland, & Janosky, 1992; Vargha-Khadem, Isaacs, & Muter,

Language is the crowning achievement of the human species, and it is something that all normal humans can do. The average man is neither a Shakespeare nor a Caravaggio, but he is capable of fluent speech, even if he cannot paint at all. In fact, the average speaker produces approximately 150 words per minute, each word chosen from somewhere between 20,000 and 40,000 alternatives, at error rates below 0.1%. The average child is already well on her way toward that remarkable level of performance by 5 years of age, with a vocabulary of more than 6000 words and productive control over almost every aspect of sound and grammar in her language. Given the magnitude of this achievement, and the speed with which we attain it, some theorists have

Development and early focal brain injury 2 Over the past ten years, we have made significant progress in addressing key questions concerning deficit and development after early stroke. We found evidence of subtle early impairment and subsequent development in each domain examined. However, the profiles of impairment and development differed across domains. Deficits of language acquisition are initially pervasive in that they are observed following injury to widely distributed brain areas. Spatial analytic deficits exhibit more specific patterns of brain-behavior association, similar to those observed among adults with injury to comparable brain regions. Had we been working in isolation, the separate investigators associated with this project may have reached very different conclusions about the nature of development following early injury. Instead, we were forced to look for ways to resolve the apparent disparity in our cross-domain findings. The model that best fits our data focuses on redefining the nature of early plasticity. Recent animal studies provide strong evidence that plasticity plays a central role in brain development. Brain organization is to a large extent