Profiles of Color Synesthesia
The NeCoSyn Method

Crétien van Campen & Clara Froger


Presentation ASA conference San Diego, Sunday 18 May 2002

This page contains the text that was read by Carol Steen. To see the slides of the presentation click here.


slide 1

Profiles of Color Synesthesia
The NeCoSyn Method

Crétien van Campen & Clara Froger

This is a cooperative project by an artist and a  scientist. Clara and I  were both studying synesthesia  when we met, about five years ago. She was experimenting with the colors of music, taste, and odors among other senses. I was testing self-reported synesthetes. Clara was one of the synesthetes who was tested and she criticized the concept of color that was used and so started a long critical interaction that has resulted in a method that we are both very pleased to have presented here today.

We apologize for not being physically present. Actually we are somewhere on the other side of the planet as is indicated on the picture of the globe on the slide. We live in the Netherlands: Clara is in the world's largest harbour city Rotterdam and Crétien is in the medieval town of Utrecht. We are very grateful to Carol Steen that she is willing to present our paper. We are very glad that our ideas are being communicated here today .

In this presentation, we would like to show you the NeCoSyn method, which stands for the Netherlands Color Synesthesia method. It has been designed to capture the rich and various synesthetic experiences in individual profiles. Reading the books and papers and self-reports of synesthetes, the synesthetic phenomenon seems to have many aspects, varieties, and types. Many synesthetes report having several types of synesthesia. Every synesthete seems unique yet on closer observation there are similarities between synesthetes that start to become apparent.

Can we compare the experiences of synesthetes? Can we show synesthetes how their experiences relate to the experiences of other synesthetes? And if so, in what terms?


Slide 2

Measuring synesthesia in:
several types (of synesthesia)

dimensions of color experiences

The easiest way to compare personal characteristics is to measure those characteristics. Our object was to develop a method to measure synesthesia and take into account :

a) the several types of synesthesia (e.g. word-color, music-color, taste-color, odor-color synesthesia) and:
b) the dimensions of color experiences (hue, saturation, brightness)
(note: these color concepts will be explained later)

slide 3

Two questions were central:
Who is a synesthete?
What are the dimensions of synesthesia?

How did we develop the method? We integrated scientific and artistic methods to answer two central questions: a) Who is a synesthete? b) What are the dimensions of synesthesia? We will go into these questions in more detail.

slide 4

To be or not to be a synesthete…
Consistency test

The first question we had to deal with was: Who is a synesthete? And who is not?

Determining or diagnosing the presence of synesthesia is a complex matter because synesthesia is not a readily observable characteristic in people. Diagnosis has to rely on self-reports and on psychological testing. The purpose of diagnosis and testing is to distinguish people with synesthetic experiences from people without them. In the last two decades several

methods have been developed to determine, diagnose, assess and distinguish synesthetes and their synesthetic experiences.

The consistency test is the most often used method by scientists. In short, the test distinguishes synesthetes from non-synesthetes by measuring the strength of their word-color correspondences over time. This test was developed by Simon Baron-Cohen and his colleagues in the 1980's. For our method, we translated the English version into Dutch. The first

Dutch version consisted of 50 words, containing words from four semantic categories (animals, towns, objects, professions), letters of the alphabet, days of the week, nonsense words, and abstract words. Later we improved and shortened the list to 25 words, including abstract words, numbers and days of the week.

Slide 5

Types of synesthesia (dimensions part I)

The second central question "What are the dimensions of synesthesia?" was investigated in two ways. First, we looked at different types of synesthesia. This slide shows a table of the various types of synesthesia, based on the research by Sean Day, into the incidence or frequency of  types of synesthesia. The colored (green and red) areas shows types of color synesthesia. The red area shows the types of color synesthesia we have included in our study so far. (Note: additional types may be  included in the future too, we will return to this point in our conclusion.).

On the basis of this table you may think we have covered only a small part of population of synesthetes, but in fact we have covered the majority because the types we have included are the most often reported ones. 

Slide 6

Color dimensions (part II)

Another way we approached dimensions of color synesthesia was to look at the dimensions of the (evoked) color experiences. When we normally speak of color we refer to hue or color tone. In fact two other elements make up the colors that we see:

1) Brightness  i.e. the amount of blackness in a color (e.g. adding black to a red hue makes it brown), and

2) Saturation is the purity of a color (e.g. candy red is highly saturated and pastel red, often called pink, is much less saturated).  

We chose the Natural Color System to distinguish these three dimensions of color, Hue, Brightness and Saturation. The Natural Color System is a logical color system built on how humans see color. This system is based on color perceptions and differs in this respect from most other color systems that are based on the mixing of paint or pigments. The notations are less technical and therefore more understandable and usable for laymen.

In this slide you see NCS colour space and one section. The color space represents all the possible colors and consists of three dimensions:
The horizontal circle is built on the four basic hues: yellow, red, blue and green.

The vertical axis adds brightness (lightness) or blackness to the hue (black-white), and
The horizontal axis indicates the amount of saturation from no saturation
in the middle to full saturation in the outer sphere.

As an example the slide shows one cross-section of the color space (note: unfortunately the projection of the colors is not ideal): The color purple at the right angle is a hue between red and blue. Going up the color changes into lighter purple, almost grey-blue. Going down the color changes into darker purple, almost black. Going to the center of the space the purple gets less saturated (not clearly visible in this slide). 

Slide 7

The test

We invited self-reported synesthetes and asked them to choose color chips that fit best with their color experiences or associations with words, music, tastes and odors. In this slide you see a picture taken during the experiment with odor-colors. Participating synesthetes (on the left) smell odors with their eyes shut and then choose corresponding colors from the selection of color chips on the table. Afterwards, the assistants (on the right) note the numbers (on the back the color chips) that contain  NCS information of hue, saturation and brightness. One of the experimentators (in the back) keeps watch. 

Slide 8

Materials: selection of colors

What materials did we use in our study? First, Clara Froger, our expert on color, selected a representative selection of 118 color chips out of the hundreds of color chips in the NCS standard. In this slide you can see the palette of colors from which the participating synesthetes could choose.  

Slide 9

As stimuli to evoke color experiences we presented the participants with:
a) a selection of 25 words. The adaptation of the English consistency test (mentioned earlier).
b) a selection of tape recordings of 11 musical instruments chosen from a variety of wind and stringed instruments. We had taped musical pieces (in the key of D) played by members of the Rotterdam Philharmonic Orchestra (who had great fun doing it and wondered what this syn-thing was all about).
c) a selection of 11 tastes, a wide range of tastes including the dimensions sweet, sour, bitter and salty. We consulted a cook.
d) a selection of 11 odors, a wide range of odors. We consulted professional odor experts. 

Slide 10

Tasting colors

See how the participants tasted the selected flavours (with their eyes shut) and then chose their colors. (Note: drinking water was given to our "poor guinea pigs",between two stimuli .

Slide 11

NeCoSyn profile of a synesthete

This slide shows an example of a NeCoSyn profile of one of the synesthetes who participated in our study. Before she participated in the study, this synesthete reported that she experiences words in color and that she uses colors while cooking. The profile provides some additional interesting information and details.

First, we will explain how to read the profile. The NeCoSyn profile consists of four types of synesthesia (see vertical axis) (word-color, music-color, taste-color, odor-color). Each type has three color dimensions (see colored bars):
the yellow-blue bar represents hue, the reddish bar saturation and the light-dark bar brightness).
The length of each bar indicates the strength of synesthesia, categorized into weak, moderate, and strong (see horizontal axis on top).

The NeCoSyn profile provided a detailed insight in her color synesthesia. Her color-word synesthesia is very strong on all dimensions of color. Her color-taste synesthesia (that she uses for cooking) is based on very strong dimensions of saturation and brightness of color-taste. The hue dimension is weaker. i.e. she experiences tastes mostly  in the dark-lightness scale and less in specific hues or color tones. The NeCoSyn test revealed another perceptual competence, which she did not report before: she has a very strong ability to perceive the brightness of odors. Scents appear in darker or lighter tones to her.

Slide 12

Applications in art
- practical tool for artists
- input for musical visualizers (multimedia)
- material for art education

In general the NeCoSyn profiles are maps of someone's individual color synesthesia. Since they are scaled, the profiles can be compared to profiles of other synesthetes and group means. We are now looking for possible applications of this method in the fields of the arts and sciences.

In the fields of the arts, the NeCoSyn profiles can be used as an analytic tool by individual artists for understanding and gaining more detailed insight in their personal synesthetic experiences. Compare for instance how synesthetic artists like Carol Steen and David Hockney have profited from more insight in their synesthetic experiences.

The results of the NeCoSyn method can be used as an input for the creative process. Fred Collopy and Harley Gittleman at this conference have shown how knowledge of synesthetic correspondences is put into musical visualizers and other multimedia instruments.

In art schools, art educators can use the NeCoSyn method and profiles to teach students about their personal perceptual functioning and sensibilities. In the process of developing our method we tested a group of more than 200 art students. The testing revealed synesthesia to some students (made them aware of their synesthetic abilities) and stimulated discussions of synesthesia and sensibility in others.

Slide 13

Applications in science
- supplement to consistency tests

- comparison with subjective reports and brain imaging     results
- new light on incidence of synesthesia?

For scientific disciplines, e.g. medical and social sciences, the NeCoSyn method  provides a supplement to existing consistency methods. The main advantages over the color-word test of Baron-Cohen et al. are the assessment on color dimensions and the extensions to other types of color synesthesia.

In comparison with the method of self-report by synesthetes we found in our interviews with participants that self-reports are not always in line with the test results. Another point is that the subjective intuition of participants was objectified and specified by the NeCoSyn instrument. In particular the extra information on color dimensions of synesthetic experiences was new to the participants. In comparison with brain imaging, the NeCoSyn is far less expensive to administer, less of a burden on participants and can therefore be used for larger scale group testing . One of our subjects was tested in the medical lab of Utrecht University (Aleman et al. 2002). In future research it will be interesting to compare the results of brain imaging with the NeCoSyn profiles of synesthetes.

The incidence or frequency of synesthesia still is a big question mark in synesthesia research. To outsiders the frequency or  incidence rates of 1:20 (Galton) 1:200 (Hubbard & Ramachandran), 1:2000 (Baron-Cohen cs) and 1:20,000 (Cytowic) might raise the question : What is synesthesia research about? The incidence has to do with the number 2 but we don't know how zero's we have to add.

As a step aside, we have the impression that our results may shed new light on determining the frequency of synesthesia. Current research into the frequency of color synesthesia is focused on color tone or hue. In the four types of synesthesia we measured, the mean scores for brightness and saturation were higher than the scores on hue.

When we counted the frequency of synesthetes according to the existing consistency test (only hue) and to NeCoSyn methods we found frequencies for saturation and brightness were almost double the frequency of the existing test for hue or color tone. We concluded that frequency differs with the color dimension you look at. This is not as strange as it seems if we remember that many people experience the sound of a bass as dark but few people experience it as yellow or purple. This distinction between hue on the one side and brightness and saturation on the other side might have a link with the distinction Martino & Marks have made between strong and weak synesthesia. We are investigating this with other scientists in the Netherlands at the moment.

Slide 14

- a practical method for artists and scientists
- extension to other types of synesthesia
- art and science of synesthesia

To conclude, the NeCoSyn method offers a practical system that can be applied by both artists and scientists. In our present study we restricted ourselves to four types of color synesthesia, but the NeCoSyn method can be applied to more sensory domains. We give the example of assessing color-tactile synesthesia. Take little black sacs containing substances with different textures inside. Let people choose colors after touching the textures inside. One can vary with cold and warm textures, fine versus coarse, etcetera.

That means that the NeCoSyn method is not finished. The artistic and scientific study of synesthesia has grown along separate lines, more by tradition than by logic. The NeCoSyn is an example that critical interaction of both disciplines can deepen our insight into synesthesia and probably multisensory sensibilities in general.

Slide 15

More info:
For questions and remarks
mail to: or

We thank you for attention and hope you will respond to our method.
More info is on the website
(note the last e not a).
The site contains an online report of our study in English.
Though not physically present today, we are eager to hear your questions and remarks by e-mail
mail to: or