how one can judge the native-like quality of the speech participants produce and what exactly it means to be a near-native speaker of a second language. White et al. found that it is possible for non-native speakers of a language to become native-like in some aspects, but those aspects are influenced by their first language. Recently, a connectionist model has been developed to explain the changes that take place in second language learning assuming that sensitive period affects lexical learning and syntactic learning parts of the system differently, which sheds further light on how first and second language acquisition changes over the course of learners development. Vision In mammals, neurons in the brain that process vision actually develop after birth based on signals from the eyes. A landmark experiment by David H. Hubel and Torsten Wiesel (1963) showed that cats that had one eye sewn shut from birth to three months of age (monocular deprivation) only fully developed vision in the open eye. They showed that columns in the primary visual cortex receiving inputs from the other eye took over the areas that would normally receive input from the deprived eye. In general electrophysiological analyses of axons and neurons in the lateral geniculate nucleus showed that the visual receptive field properties was comparable to adult cats. However, the layers of cortex that were deprived had less activity and fewer responses were isolated. The kittens had abnormally small ocular dominance columns (part of the brain that processes sight) connected to the closed eye, and abnormally large, wide columns connected to the open eye. Because the critical period time had elapsed, it would be impossible for the kittens to alter and develop vision in the closed eye. This did not happen to adult cats even when one eye was sewn shut for a year because they had fully developed their vision during their critical period. Later experiments in monkeys found similar results consistent with the strong critical period. In a follow-up experiment, Hubel and Wiesel (1963) explored the cortical responses present in kittens after binocular deprivation; they found it difficult to find any active cells in the cortex, and the responses they did get were either slow-moving or fast-fatiguing. Furthermore, the cells that did respond selected for edges and bars with distinct orientation preferences. Nevertheless, these kittens developed normal binocularity. Hubel and Wiesel first explained the mechanism, known as orientation selectivity, in