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The Best PhD Thesis in the Faculties of Dentistry, Engineering, Medicine and Science (University of Hong Kong), Li Ka Shing Prize,1999-2001 / published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of California, San Diego, 2003. / Vita. Includes bibliographical references (leaves 211-216).

Previous behavioral and neuroimaging findings (Drivonikou, et al., 2007; Gilbert, et al., 2006; Tan, et al., 2008; Siok, et al., 2009) indicate that reaction times to targets in visual search are faster in the right than the left visual field when the target and distractor colors straddle a category boundary. This phenomenon is known as the lateralized categorical color perception, which supports the weaker form of Whorf’s hypothesis that linguistic information shapes color perception. Yet, these studies did not demonstrate a definite cause and effect relation between language and perception. The observed lateralized category effect of color perception may either rely on the individual’s innate color categories or his linguistic experience. In the present study, we used an intensive training method to study categorical perception (CP) of color. We aimed to show a definite causal relation between language and perception. In Experiment 1, 37 native Mandarin speakers were tested with a color discrimination task. We taught 20 participants four new linguistic items for the four stimulus colors which were initially from the same lexical category (two blues and two greens) whilst other participants did not learn any new color names. Performances between the two groups were compared before and after training. Experiment 2 was based on Zhou et al.’s (2010) behavioral study, in which we used the same training procedure and measured and contrasted 19 participants’ brain structure before and after training. In experiment 1, participants exhibited lateralized Whorf effect when performing the visual search task at the pre-training phase. After training, the experimental group successfully acquired the new color names, reflected by overall shorter reaction time and higher task accuracy, while the control group did not show significant difference in the performance across two phases. The improved performance of experimental group implicated that the newly learned categories altered participants’ color perception pattern. However, we failed to show lateralized Whorf effect at the post-training phase due to several experimental flaws. In Experiment 2, gray matter density is found to increase in color region of the left visual cortex after a short-term training (less than two hours). The data provided strong structural evidence for newly-learned categorical color perception and also suggested structural plasticity of the human brain. The results from this study indicate that language experience shapes perception, both functionally and structurally, after a period of learning that is much shorter than previously established (Draganski, 2004; Carreiras, et al., 2009; Trachtenberg, 2002). / published_or_final_version / Linguistics / Master / Master of Philosophy

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