Unconscious priming eliminates automatic binding of colour and alphanumeric form in synaesthesia


Synaesthesia is an unusual perceptual phenomenon in which events in one sensory modality induce vivid sensations in another1,2. Individuals may ‘taste’ shapes3, ‘hear’ colours4, or ‘feel’ sounds5. Synaesthesia was first described over a century ago6, but little is known about its underlying causes or its effects on cognition. Most reports have been anecdotal or have focused on isolated unusual cases3,7,8,9. Here we report an investigation of 15 individuals with colour-graphemic synaesthesia, each of whom experiences idiosyncratic but highly consistent colours for letters and digits. Using a colour–form interference paradigm, we show that induced synaesthetic experiences cannot be consciously suppressed even when detrimental to task performance. In contrast, if letters and digits are presented briefly and masked, so that they are processed but unavailable for overt report, the synaesthesia is eliminated. These results show that synaesthetic experiences can be prevented despite substantial processing of the sensory stimuli that otherwise trigger them. We conclude that automatic binding of colour and alphanumeric form in synaesthesia arises after initial processes of letter and digit recognition are complete.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Mean (+1 s.e.) consistency of colour associations for 150 items (letters, arabic numerals and words), plotted separately for each of 11 categories tested.
Figure 2: Mean voice-onset times (±1 s.e.) for colour naming in the standard and synaesthetic Stroop tasks, plotted as a function of congruency condition.
Figure 3: Mean percentage correct prime identification (+1 s.e.) for the priming experiments.
Figure 4: Mean voice-onset times (±1 s.e.) for colour naming in the visible priming (500 ms) and masked priming (56 and 28 ms) experiments, plotted as a function of synaesthetic congruency condition.


  1. 1

    Baron-Cohen, S. & Harrison, J. E. (eds) Synaesthesia: Classic and Contemporary Readings (Blackwell, Cambridge, 1997).

    Google Scholar 

  2. 2

    Cytowic, R. E. Synesthesia: A Union of the Senses (Springer, New York, 1989).

    Google Scholar 

  3. 3

    Cytowic, R. E. The Man Who Tasted Shapes (Abacus, London, 1993).

    Google Scholar 

  4. 4

    Baron-Cohen, S., Wyke, M. A. & Binnie, C. Hearing words and seeing colours: an experimental investigation of a case of synaesthesia. Perception 16, 761–767 (1987).

    CAS  Article  Google Scholar 

  5. 5

    Luria, A. R. The Mind of a Mnemonist (Basic Books, London, 1969).

    Google Scholar 

  6. 6

    Galton, F. Visualized numerals. Nature 21, 252–256 (1880).

    ADS  Article  Google Scholar 

  7. 7

    Mills, C. B., Boteler, E. H. & Oliver, G. K. Digit synaesthesia: A case study using a Stroop-type test. Cog. Neuropsychol. 16, 181–191 (1999).

    Article  Google Scholar 

  8. 8

    Odgaard, E. C., Flowers, J. H. & Bradman, H. L. An investigation of the cognitive and perceptual dynamics of a colour-digit synaesthete. Perception 28, 651–664 (1999).

    CAS  Article  Google Scholar 

  9. 9

    Wollen, K. A. & Ruggiero, F. T. Colored-letter synaesthesia. J. Mental Imagery 83–86 (1983).

  10. 10

    Baron-Cohen, S., Burt, L., Smith-Laittan, F., Harrison, J. & Bolton, P. Synaesthesia: prevalence and familiality. Perception 25, 1073–1079 (1996).

    CAS  Article  Google Scholar 

  11. 11

    Dixon, M. J., Smilek, D., Cudahy, C. & Merikle, P. M. Five plus two equals yellow. Nature 406, 365 (2000).

    ADS  CAS  Article  Google Scholar 

  12. 12

    Paulesu, E. et al. The physiology of coloured hearing: A PET activation study of colour-word synaesthesia. Brain 118, 661–676 (1995).

    Article  Google Scholar 

  13. 13

    Baron-Cohen, S., Harrison, J., Goldstein, L. H. & Wyke, M. Coloured speech perception: is synaesthesia what happens when modularity breaks down? Perception 22, 419–426 (1993).

    CAS  Article  Google Scholar 

  14. 14

    Stroop, J. R. Studies of interference in serial verbal reactions. J. Exp. Psychol. 18, 643–662 (1935).

    Article  Google Scholar 

  15. 15

    MacLeod, C. M. Half a century of research on the Stroop effect: an integrative review. Psychol. Bull. 109, 163–203 (1991).

    CAS  Article  Google Scholar 

  16. 16

    Dehaene, S. et al. Imaging unconscious semantic priming. Nature 395, 597–600 (1998).

    ADS  CAS  Article  Google Scholar 

  17. 17

    Forster, K. I. & Davis, C. Repetition priming and frequency attenuation in lexical access. J. Exp. Psychol. Learn. Mem. Cog. 10, 680–698 (1984).

    Article  Google Scholar 

  18. 18

    Marcel, A. J. Conscious and unconscious perception: experiments on visual masking and word recognition. Cog. Psychol. 15, 197–237 (1983).

    CAS  Article  Google Scholar 

  19. 19

    Grossenbacher, P. G. in Synaesthesia: Classic and Contemporary Readings (eds Baron-Cohen, S. & Harrison, J. E.) (Blackwell, Cambridge, 1997).

    Google Scholar 

Download references


We wish to thank A. Kritikos, M. O'Boyle, P. Wilken and M. Williams for their comments on the manuscript. This work was supported by a grant from the Australian Research Council to J.B.M.

Author information



Corresponding author

Correspondence to Jason B. Mattingley.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Mattingley, J., Rich, A., Yelland, G. et al. Unconscious priming eliminates automatic binding of colour and alphanumeric form in synaesthesia. Nature 410, 580–582 (2001). https://doi.org/10.1038/35069062

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Sign up for the Nature Briefing newsletter for a daily update on COVID-19 science.
Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing