People with color-grapheme synesthesia experience color when viewing written letters or numerals, usually with a particular color evoked by each grapheme. Here, we report on data from 11 color-grapheme synesthetes who had startlingly similar color-grapheme pairings traceable to childhood toys containing colored letters. These are the first and only data to show learned synesthesia of this kind in more than a single individual. Whereas some researchers have focused on genetic and perceptual aspects of synesthesia, our results indicate that a complete explanation of synesthesia must also incorporate a central role for learning and memory. We argue that these two positions can be reconciled by thinking of synesthesia as the automatic retrieval of highly specific mnemonic associations, in which perceptual contents are brought to mind in a manner akin to mental imagery or the perceptual-reinstatement effects found in memory studies.
AlexanderJ. D.NygaardL. C. (2008). Reading voices and hearing text: Talker-specific auditory imagery in reading. Journal of Experimental Psychology: Human Perception and Performance, 34, 446–459. doi:10.1037/0096-1523.34.2.446
2.
BarnettK. J.FinucaneC.AsherJ. E.BargaryG.CorvinA. P.NewellF. N.MitchellK. J. (2008). Familial patterns and the origins of individual differences in synaesthesia. Cognition, 106, 871–893. doi:10.1016/j.cognition.2007.05.003
BeeliG.EsslenM.JänckeL. (2007). Frequency correlates in grapheme-color synaesthesia. Psychological Science, 18, 788–792. doi:10.1111/j.1467-9280.2007.01980.x
5.
BerensB. (2009). CircStat: A MATLAB toolbox for circular statistics. Journal of Statistical Software, 31(10). Retrieved from http://www.jstatsoft.org/v31/i10/paper
6.
BlakeR.PalmeriT. J.MaroisR.KimC.-Y. (2005). On the perceptual reality of synesthetic color. In RobertsonL. C.SagivN. (Eds.), Synesthesia: Perspectives from cognitive neuroscience (pp. 47–73). New York, NY: Oxford University Press.
7.
CalkinsM. W. (1893). A statistical study of pseudo-chromesthesia and of mental forms. American Journal of Psychology, 5, 439–464.
8.
Cohen KadoshR.HenikA. (2007). Can synaesthesia research inform cognitive science?Trends in Cognitive Sciences, 11, 177–184. doi:10.1016/j.tics.2007.01.00310.1016/j.cognition.2006.12 .007
9.
EaglemanD. E.KaganA. D.NelsonS. S.SagaramD.SarmaS. K. (2007). A standardized test battery for the study of synesthesia. Journal of Neuroscience Methods, 159, 139–145. doi:10.1016/j.jneumeth.2006.07.012
10.
EaglemanD. M. (2009). The objectification of overlearned se- quences: A new view of spatial sequence synesthesia. Cortex, 45, 1266–1277. doi:10.1016/j.cortex.2009.06.012
11.
GaltonF. (1881). Visualized numerals. Journal of the Royal Anthropological Institute, 10, 85–102.
12.
HancockP. (2006). Monozygotic twins’ colour-number association: A case study. Cortex, 42, 147–150. doi:10.1016/S0010-9452(08)70338-1
13.
HarrisonS. A.TongF. (2009). Decoding reveals the contents of visual working memory in early visual areas. Nature, 458, 632–635. doi:10.1038/nature07832
14.
HubbardE. M.RamachandranV. S. (2005). Neurocognitive mechanisms of synesthesia. Neuron, 48, 509–520. doi:10.1016/j.neuron.2005.10.012
15.
KellyE. L. (1934). An experimental attempt to produce artificial chrom- aesthesia by the technique of conditioned response. Journal of Experimental Psychology,17, 315–341. doi:10.1037/h0074963
KimC.-Y.BlakeR.PalmeriT. J. (2006). Perceptual interaction between real and synesthetic colors. Cortex, 42, 195–203. doi:10.1016/S0010-9452(08)70344-7
18.
MarksL. E. (1974). On associations of light and sound: The mediation of brightness, pitch, and loudness. American Journal of Psychology, 87, 173–188.
19.
MarksL. E. (1975). On colored-hearing synesthesia: Cross-modal translations of sensory dimensions. Psychological Bulletin, 82, 303–331. doi:10.1037/0033-2909.82.3.303
20.
MarksL. E.OdgaardE. C. (2005). Developmental constraints on theories of synesthesia. In RobertsonL. C.SagivN. (Eds.), Synesthesia: Perspectives from cognitive neuroscience (pp. 214–236). New York, NY: Oxford University Press.
21.
MartinoG.MarksL. E. (2001). Synesthesia: Strong and weak. Current Directions in Psychological Science, 10, 62–65. doi:10.1111/1467-8721.00116
22.
McDermottJ. H.LehrA. J.OxenhamA. J. (2008). Is relative pitch specific to pitch?Psychological Science, 19, 1263–1271. doi:10.1111/j.1467-9280.2008.02235.x
23.
NovichS.ChengS.EaglemanD. M. (2011). Is synaesthesia one condition or many? A large-scale analysis reveals subgroups. Journal of Neuropsychology, 5, 353–371. doi:10.1111/j.1748-6653.2011.02015.x
24.
PaivioA. (1969). Mental imagery in associative learning and memory. Psychological Review, 76, 241–263. doi:10.1037/h0027272
25.
PylyshynZ. W. (2002). Mental imagery: In search of a theory. Behavioral Brain Sciences, 25, 157–182.
26.
RamachandranV. S.HubbardE. M. (2001a). Psychophysical investigations into the neural basis of synaesthesia. Proceedings of the Royal Society B: Biological Sciences, 268, 979–983. doi:10.1098/rspb.2001.1576
27.
RamachandranV. S.HubbardE. M. (2001b). Synaesthesia: A window into perception, thought and language. Journal of Consciousness Studies, 8, 3–34.
28.
RichA. N.BradshawJ. L.MattingleyJ. B. (2005). A systematic, large-scale study of synaesthesia: Implications for the role of early experience in lexical-colour associations. Cognition, 98, 53–84. doi:10.1016/j.cognition.2004.11.003
29.
SimnerJ. (2005). Non-random associations of graphemes to colours in synaesthetic and non-synaesthetic populations. Cognitive Neuropsychology, 22, 1–17. doi:10.1080/02643290500200122
30.
SimnerJ.HarroldJ.CreedH.MonroL.FoulkesL. (2009). Early detection of markers for synaesthesia in childhood populations. Brain, 132, 57–64. doi:10.1093/brain/awn292
31.
SimnerJ.MulvennaC.SagivN.TsakanikosE.WitherbyS. A.FraserC.. . . WardJ. (2006). Synaesthesia: The prevalence of atypical cross-modal experiences. Perception, 35, 1024–1033. doi:10.1068/p5469
32.
SpectorF.MaurerD. (2009). Synesthesia: A new approach to understanding the development of perception. Developmental Psychology, 45, 175–189. doi:10.1037/a0014171
33.
TomsonS. N.AvidanN.LeeK.SarmaA. K.TusheR.MilewiczD. M.. . . EaglemanD. M. (2011). The genetics of colored sequence synesthesia: Suggestive evidence of linkage to 16q and genetic heterogeneity for the condition. Behavioral Brain Research, 223, 48–52. doi:10.1016/j.bbr.2011.03.071
34.
TylerC. (2005). Varieties of synesthetic experience. In RobertsonL. C.SagivN. (Eds.), Synesthesia: Perspectives from cognitive neuroscience (pp. 34–44). New York, NY: Oxford University Press.
35.
WardJ.MattingleyJ. B. (2006). Synaesthesia: An overview of contemporary findings and controversies. Cortex, 42, 129–136. doi:10.1016/S0010-9452(08)70336-8
36.
WardJ.SimnerJ. (2003). Lexical-gustatory synaesthesia: Linguistic and conceptual factors. Cognition, 89, 237–261. doi:10.1016/S0010-0277(03)00122-7
37.
WheelerM. E.PetersenS. E.BucknerR. L. (2000). Memory’s echo: Vivid remembering reactivates sensory-specific cortex. Proceedings of the National Academy of Sciences, USA, 97, 11125–11129. doi:10.1073/pnas.97.20.11125
38.
WinawerJ.HukA. C.BoroditskyL. (2010). A motion aftereffect from visual imagery of motion. Cognition, 114, 276–284.
39.
WitthoftN.WinawerJ. (2006). Synesthetic colors determined by having colored refrigerator magnets in childhood. Cortex, 42, 175–183. doi:10.1016/S0010-9452(08)70342-3
Supplementary Material
Please find the following supplemental material available below.
For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.
For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.
