Word learning in context : the role of lifetime language input and sentential context

Our experience with words defines how we understand them. In this dissertation, I examine how two kinds of experience influence how words are learned-that of "global" lifetime language experience, and "local" experience from immediate linguistic context. Computational simulations are used in the first set of experiments to simulate a variety of early language learning environments that vary in amount, frequency, complexity of linguistic input. Brainwave experiments are used in the second set of studies to probe the neural and cognitive correlates of word learning from sentential context. The first set of studies are computational simulations that explore how differences in linguistic experience can explain differences in word learning ability and organization of semantic knowledge. We varied the amount of language input, sentential complexity, and the frequency distribution of words within categories. In each simulation, improvements in category structure were tightly correlated with subsequent improvements in word learning ability. These simulations suggest that vast differences in lexical proficiency in children can at least partly be explained by differences in early language environments and underlying cognitive abilities like categorization. The second set of studies explore how local experience influences single-shot word learning in a series of three brainwave studies. Adult participants read known and unknown words in high and low constraint sentences and then made plausibility judgments on their usage in subsequent sentences, or saw these words again as primes in a semantic priming task. These studies found that participants were able to integrate knowledge about the meaning and usage of unknown words that initially appeared in highly constraining contexts, but not low constraint contexts. In addition, a lateralized version of the semantic priming probe task revealed that the right hemisphere initially participates in the semantic priming of novel words. Together these studies highlight the importance of experience in acquisition of word meaning, and reveal that the brain is able to quickly acquire significant and sophisticated information about word meanings after only a single instance. In addition, these studies suggest a method by which lexical acquisition can be measured via electrical brain activit