When: Wednesday, August 7, 2019 at 12:30 PM
Where: Room 355, Friedman Building, 2177 Wesbrook Mall
Title: Neural underpinnings of orthography in first and second language readers
Candidate: Osamu Takai
Committee: Anthony Herdman, Jeff Small, Deborah Giaschi, Janet Werker
Abstract:
Reading success in a second language (L2) is crucial for billions of people worldwide, but it is well known that it remains difficult for L2 learners to automatize the L2 processing in general. I investigated how long-term reading experience in a first language (L1) might change the neural L1 orthographic processing, and if these results can be generalized to L2 orthographic processing. I recruited adult monolingual English readers and late adult English learners of Mandarin readers. By contrasting single-letters with pseudoletter visual stimuli (a pseudoletter effect) in L1, the reaction time data showed that reading experience makes letter processing faster than in pseudoletter processing. The magnetoencephalography data showed that the L1 pseudoletter effect was manifested in a left-dominant oscillatory activity and network dynamics. The electroencephalogram data showed that the L1 pseudoletter effect was robust, regardless of the level of attention paid; letters elicited more of left-lateralized neural connectivity desynchronization than did pseudoletters. Additionally, electroencephalogram data from L2 showed that the magnitude of the L2 pseudoletter effect in the N170 in the left hemisphere was correlated with L2 proficiency. Taken together, I concluded that with reading experience, the brain has automatized orthographic processing, which is evidenced by being (1) more specific by shifting the processing demands to different neural regions within visual processing networks—left dominant for well experienced orthographies (2) being more obligatory at least at the single-letter level (3) faster by completing the process of differentiating letters from pseudoletters at fairly early stages of visual processing. Further I concluded that some of the above changes appear to be ready throughout adulthood; orthographic development appears to be free from the fossilization or critical period hypotheses.
Lay Summary:
Reading success in a second language (L2) is crucial for billions of people worldwide. Yet, late L2 readers continue to struggle with L2 processing being slow and effortful, compared to first language (L1) processing being fast and effortless. I investigated how single alphabet letters and Chinese characters were processed for adult monolingual English readers and late adult English learners of Mandarin readers. What changes does L1 reading bring? Are these changes limited in early in life? The results of my research indicate that the brain has built a system for L1 processing which is faster, more specific and efficient than processing unfamiliar visual symbols. The results also imply that such changes continue to take place throughout adulthood. Thus, while late L2 readers might continue to struggle with L2 language processing (e.g., vocabulary and grammar), visual single-letter processing appears to be an area that L2 readers can keep polishing.