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Grapheme → color synesthesia is a form of synesthesia in which an individual's perception of numbers and letters is associated with the experience of colors. Like all forms of synesthesia, grapheme → color synesthesia is involuntary, consistent, and memorable.〔Grossenbacher, P. G., Lovelace, C. T. (2001). Mechanism of synesthesia: Cognitive and physiological constraints. Trends in Cognitive Sciences, (5)1, 36–41. 〕 Grapheme → color synesthesia is one of the most common forms of synesthesia, and because of the extensive knowledge of the visual system, one of the most studied.〔Jäncke, L., Beeli, G., Eulig, C., & Hänggi, J. (2009). The neuroanatomy of grapheme–color synesthesia. European Journal Of Neuroscience, 29(6), 1287–1293. doi:10.1111/j.1460-9568.2009.06673.x〕 While it is extremely unlikely that any two synesthetes will report the same colors for all letters and numbers, studies of large numbers of synesthetes find that there are some commonalities across letters (e.g., "A" is likely to be red).〔Day, S.A. (2005), "Some Demographic and Socio-cultural Aspects of Synesthesia" in L. Robertson & N. Sagiv, ed., Synesthesia: Perspectives from Cognitive Neuroscience, Oxford: Oxford University Press, ISBN 0-19-516623-X, pp. 11–33〕〔Simner, J., Ward, J. & Lanz, M., et al. (2005), "Non-random associations of graphemes to colours in synaesthetic and non-synaesthetic populations", Cognitive Neuropsychology, vol. 22, no. 8, pp. 1069–1085〕 Early studies argued that grapheme → color synesthesia was not due to associative learning, such as from playing with colored refrigerator magnets.〔Ramachandran, V.S. & Hubbard, E.M. (2001), "(Synaesthesia: A window into perception, thought and language )", Journal of Consciousness Studies, vol. 8, no. 12, pp. 3–34〕 However, one recent study has documented a case of synesthesia in which synesthetic associations could be traced back to colored refrigerator magnets.〔Witthoft, N. & Winawer, N. (2006), "Synesthetic colors determined by having colored refrigerator magnets in childhood", Cortex, vol. 42, no. 2, pp. 175–183.〕 Despite the existence of this individual case, the majority of synesthetic associations do not seem to be driven by learning of this sort.〔〔Rich, A. N., Bradshaw, J. L. & Mattingley, J. B. (2005), "A systematic, large scale study of synaesthesia: Implications for the role of early experience in lexical-colour associations", Cognition, vol. 98, no. 1, pp. 53–84〕 Rather, it seems that more frequent letters are paired with more frequent colors, and some meaning-based rules, such as ‘b’ being blue, drive most synesthetic associations. There has been a lot more research as to why and how synesthesia occurs with more recent technology and as synesthesia has become more well known. It has been found that grapheme-color synesthetes have more grey matter in their brain. There is evidence of an increased grey matter volume in the left caudal intra- parietal sulcus (IPS).〔Weiss, P. H., & Fink, G. R. (2009). Grapheme-colour synaesthetes show increased grey matter volumes of parietal and fusiform cortex. Brain: A Journal Of Neurology, 132(1), 65–70. doi:10.1093/brain/awn304〕 There was also found to be an increased grey matter volume in the right fusiform gyrus. These results are consistent with another study on the brain functioning of grapheme-color synesthetes. Grapheme-color synesthetes tend to have an increased thickness, volume, and surface area of the fusiform gyrus.〔 Furthermore, the area of the brain where word, letter, and color processing are located, V4a, is where the most significant difference in make-up was found. Though not certain, these differences are thought to be part of the reasoning for the presence of grapheme-color synesthesia. ==Experiences and reports== Synesthetes often report that they were unaware their experiences were unusual until they realized other people did not have them, while others report feeling as if they had been keeping a secret their entire lives. Many synesthetes can vividly remember when they first noticed their synesthetic experiences, or when they first learned that such experiences were unusual.〔 Writer and synesthete Patricia Lynne Duffy remembers one early experience: As does filmmaker Stephanie Morgenstern: As reported by poet and screenwriter Stephen Bishop 3rd: On the other hand, many synesthetes never realize that their experiences are in any way unusual or exceptional. For example, the Nobel prize winning physicist, Richard Feynman reports: While synesthetes sometimes report seeing colors projected in space, they do not confuse their synesthetic colors with real colors in the external world. Rather, they report that they are simultaneously aware of the external color and also the internal, synesthetic color: Finally, synesthetes are quite precise in the color mappings that they experience, which can lead them to make quite detailed comparisons of their colors: 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Grapheme–color synesthesia」の詳細全文を読む スポンサード リンク
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