This document summarizes research on grapheme-color synesthesia, where letters or numbers elicit color associations. The researcher analyzed patterns between letter frequencies in different languages and typical color wavelengths associated with those letters by synesthetes. Charts of collective synesthetic color associations for letters in English, Spanish and German were presented. Statistical analyses found correlations between letter frequency and average associated color wavelength. This supported the theory that synesthetic associations form as individuals learn the alphabet and remain stable. The study hypothesized that synesthetic perceptions result from excess connections between the color center V4 and left middle temporal gyrus involved in semantic processing.

1. SYNESTHETIC
ASSOCIATIONAL
PATTERNS
BETWEEN LETTERS
AND COLORS
Laura Mariah Herman |Vision Sciences Lab, Department of Psychology, Harvard University, Cambridge, MA
Pine Crest School, Fort Lauderdale, FL

2. BACKGROUND
• Synesthesia: inherent blending of the
senses.
– Grapheme-color is most common:
letters/numbers→colors
– Each synesthete associates each letter with different
colors
– Caused by excess neuronal connections per mutated
enzyme
– Single nucleotide polymorphism (16th chromosome)
• Genetically transmitted to ~0.01% of
population

3. Welcome to my world
of synesthesia!
Welcome to my world
of synesthesia!

4. QUESTION
What causes certain letters to be
associated with certain colors?
Why is this A
red?

5. MATERIALS & METHODS
• Color frequency (wavelengths) compared to letter
frequency (%)
• Synesthete color charts collective of synesthetes of
the language (color the majority of synesthetes
associated with each letter was used)
• English: dictionary vs. Brown Corpus (better
cross-section of English language) vs. children’s
books (synesthetic associations form as the subject
learns the alphabet and remain the same)
• English, Spanish, German to verify causation vs.
coincidence

6. SYNESTHETE COLOR CHARTS
English German
Spanish
0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0
0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 1 0 0 0 0 1 1 0 0 0 1
0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 1 0 0 0 1 1 0 0 0 1 0 1 0 0 0 0
0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 3 2 2 0 0 0 2 0 0 0 1 0 1 0 0
5 0 3 0 1 0 0 0 2 3 1 1 2 3 1 0 1 0
0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 1 0
0 0 1 0 1 3 0 1 0 0 2 0 0 0 0 1 1 0
0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1 0
0 0 0 0 0 0 0 1 0 1 1 2 1 1 0 0 2 0
0 0 0 1 0 1 0 0 3 0 0 0 0 2 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 2 1 0 0 0 0 0 0 0 0 0 0 0 0 0
0 1 0 0 3 0 0 0 0 0 0 0 3 0 0 2 0 0
5 2 1 0 1 0 1 1 0 0 1 0 2 2 0 3 0 0
0 0 1 0 0 0 1 2 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 1 1 0 0 0 0 0 0 1 0 0 0
1 2 1 1 0 1 1 0 0 1 1 3 0 0 0 0 1 0
0 0 0 0 0 1 0 0 0 0 0 1 1 0 0 0 0 0
0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
0 0 0 3 0 0 1 0 1 1 0 0 0 0 0 0 0 3
0 3 0 0 0 0 1 0 0 1 1 0 1 0 2 3 0 3
0 3 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 1 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0
0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0
0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0
0 0 0 0 0 0 0 1 0 0 0 0 0 2 3 0 2 0
12 12 12 11 10 11 11 11 7 10 8 9 12 13 9 10 10 7

7. DATA: FIGURE 1 (ENGLISH DICTIONARY)
Synesthetic Associational Pattern between R2= 0.6597
R² = 0.659
1000 Frequencies
Color wavelength (nm)
300
0.1 1 10 100
Frequency in the English Language (%)

8. DATA: FIGURE 2 (BROWN CORPUS)
R2= 0.45299

9. DATA: FIGURES 3 AND 4 (SPANISH/GERMAN)
Synesthetic Associational Pattern
Between Frequencies in the Spanish r² = 0.47
Language
700
Color wavelength (nm)
600
500
400
300
200
100
0
0.01 0.1 1 10
Frequency in the Spanish Language (%) Synesthetic Associational Pattern
Between Frequencies in the German
Language
700
Color wavelength (nm)
600
500
400
300
200
100
0
r² = 0.72
0.01 0.1 1 10
Frequency in the German Language (%)

10. DATA: FIGURE 5 (CHILDREN’S BOOKS)
Synesthetic Associational Pattern Between
Frequencies in Children's Books R² = 0.5656
R² = 0.565
1000
Color Wavelength (nm)
100
0 2 4 6 8 10 12 14
Letter Frequency (%)

11. NEUROPHYSIOLOGICAL THEORY
• From data, theorized which “color” and “letter” areas of the brain are fused in
synesthetes
• V4- color center in occipital lobe
– Previously suggested by fMRIs of synesthetes
– Columnar structure of neurons organized by long, middle, short wavelength
cone signals as matches previous data
– Neuron preference for more saturated and long-wavelength colors
• Left Middle Temporal Gyrus (LMTG)- semantic processing/sensory integration
– Lends itself to functional neuroconnections
– Core component of individuality of semantic system
• fusion of V4 and LMTG supported functionally and topographically

12. V4 and the LMTG. They are closely situated, as
supports the theory of their connectivity in
synesthetes.

13. DISCUSSION AND APPLICATIONS
• First synesthetic color/letter association pattern found
• Mapping of not only synesthetic connections, but also
V4/LMTG (perhaps the largely uncharted LMTG is
organized according to frequency of letters, etc.)
• Induce (visual memory, artistic talent)/reduce
(overwhelming colors for some synesthetes) synesthesia
• Autism, schizophrenia, and epilepsy also caused by
excess neuronal connections- synesthetes provide a
model brain not inhibited by medication or cognitive
impairments.
– For example, sensory areas of the brain connected with the
limbic system (anger management) in autistics, causing
simple sensory cues to extremely anger the patient

14. BIBLIOGRAPHY
Barnett, K. J., Finucane, C., Asher, J.E., Bargary, G., Corvin, A. P., Newell, F.N., Mitchell, K.J. (2007). Familial patterns
and the origins of individual differences in synaesthesia. Cognition, 106, 871-893.
Beeli, G., Esslen, M., Jancke, L. (2007). Frequency Correlates in Grapheme-Color Synesthesia. Psychological
Science, 18-9: 788-792.
Berlin, B., & Kay, P. (1969). Basic color terms: Their universality and evolution. Berkeley: University of California Press.
Emrich, H., Schneider, U., Zedler, M. Welche Farbe hat der Montag? Berlin: S. Herzel Verlag, 2004.
Kotake, Y. (2009). Organization of Color-Selective Neurons in Macaque Visual Area V4. Journal of
Neurophysiology, 102, 15-27.
Nunn, J.A., Gregory, L.J., Brammer, M., Williams, S.C.R., Parslow, D.M., Morgan, M.J., Morris, R.G., Bullmore, E.T., Ba
ron-Cohen, S., Gray, J.A. (2002) Functional magnetic resonance imaging of synesthesia: activation of V4/V8 by spoken
words. Natural Neuroscience, 4, 371-5.
Rich, A.N., Bradshaw, J.L., Mattingley, J.B. (2004). A systematic, large-scale study of synaesthesia: implications for the
role of early experience in lexical-colour associations. Cognition. 98, 53–84.
Rissman, J. (2003). An Event-Related fMRI Investigation of Implicit Semantic Priming. Journal of Cognitive
Neuroscience, 8, 1160-75.
Scullion, Val., Treby, Marrion.,(2010). Creative Synaesthesia in E. T. A. Hoffmann’s Ritter Gluck. European Review. 18:
239-262.
Wei, Tao. (2012). Predicting Conceptual Processing Capacity from Spontaneous Neuronal Activity of the Left Middle
Temporal Gyrus. Journal of Neuroscience, 32, 481-9.
Roland, D., Dick, F., & Elman, J. L. (2007). Frequency of basic English grammatical structures: A corpus
analysis. Journal of Memory and Language, 57(3), 348-379.

15. THANK YOU FOR
YOUR TIME AND
CONSIDERATION!