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Questions and Answers

Q. How common is synaesthesia?
Q. How many different types of synaesthesia are there?
Q. What is the most common type of synaesthesia?
Q. Do different synaesthetes agree on what colour letters should be?
Q. Is it possible for a synaesthete to have more than one type of synaesthesia?
Q. Is it possible for a synaesthete to have more than one type of synaesthesia?
Q. Are there any advantages or disadvantages to having synaesthesia?
Q. Are the brains of synaesthetes different?
Q. Does it run in families?
Q. Are women more likely to have synaesthesia than men?
Q. Do identical twins have identical synaesthesia?
Q. I always think of numbers/alphabet/calendar as having a particular spatial form. Is this synaesthesia?
Q. I see coloured auras around people. Is this synaesthesia?
Q. What is the youngest age at which it has been reported in the literature?
Q. Can synaesthesia ever be lost?
Q. Can synaesthesia be acquired?
Q. Is there a relationship between synaesthesia and artistic talent?
Q. Are synaesthetes more likely to be left handed?


Q.1 How common is synaesthesia?
Our current estimate is about 4% of the population, based on a study of 1700 people, each individually assessed for synaesthesia. Earlier estimates of 1 in 2000 (e.g., Baron-Cohen and colleagues, 1996) were based on replies to adverts in newspapers. This may have given rise to an underestimate because some synaesthetes may not have seen the advert, or did see it but did not reply to it.

Q.2 How many different types of synaesthesia are there?
This number is likely to be very big indeed. Not only do we have the pair-wise comparisons across the 5 senses (vision, hearing, touch, taste and smell) but we also types of synaesthesias within a single sense (e.g., seeing colours from viewing numbers). Additionally, there may be some types of synaesthesia that don’t involve the senses at all (e.g., pairing letters/numbers with specific genders and personalities).

Q.3 What is the most common type of synaesthesia?
Our recent research suggests that coloured days is probably the most common type of synaesthesia. The most commonly studied type of synaesthesia is coloured letters and digits (e.g. A=red, B=blue, 3=yellow).

Q.4 Do different synaesthetes agree on what colour letters should be?
No and yes. Two synaesthetes together will often argue over the colour of letters! But when we look at a very large sample of synaesthetes, significant preferences emerge. For instance, 'A' is often red, 'B' is often blue, 'S' is often yellow and so on. Shared preferences can also be found in other types of synaesthesia (e.g., people with coloured music tend to agree that high notes are lighter in colour than low notes).

Q.5 Is it possible for a synaesthete to have more than one type of synaesthesia?
Yes, between one third and one half of all synaesthetes have more than one type of synaesthesia, such as a person with coloured days, coloured letters, coloured numbers, shapes from tastes, and shapes from pain/touch (Day, 2005; Simner et al., in press).

Q.6 Can synaesthesia occur for touch and other bodily sensations?
Yes. For example, someone may have different shapes or colours triggered by pain or touch. One synaesthete reported different shapes for different types of headache, and would focus on the shape in an attempt to control the pain.

Q.7 Are there any advantages or disadvantages to having synaesthesia?
Synaesthesia may have some benefits on memory. For example, people with coloured numbers can recall arrays of their coloured digits better than most people. One of the most famous synaesthetes, Shereshevsky (Luria, 1966), actually made a living out of being a memory expert! Synaesthesia has no known effects on IQ and synaesthetes do not stand out from other members of society in any obvious way. Most synaesthetes are positively disposed to their synaesthesia, but for a very small number, synaesthetic perceptions may be intrusive if they are particularly intense. Finally, some synaesthetes report having difficulties with numbers and get left/right confused.

Q.8 Are the brains of synaesthetes different?
The answer to this is almost certainly 'yes', but this doesn't mean that synaesthetes are ‘brain-damaged’ in any way. Most theories of synaesthesia talk simply about ‘cross-talk’ between areas of the brain that might otherwise not communicate. For example, when certain synaesthetes hear spoken words, parts of the brain normally dedicated to colour are used (Nunn et al., 2002). This suggests that ‘word centres’ are communicating with ‘colour centres’.

Q.9 Does it run in families?
Yes. Many, if not all, synaesthetes will have a relative who has it. The relative is not always immediate family. For example, you could have a synaesthetic cousin, but have non-synaesthetic brothers and sisters. It can also skip generations. Sometimes, different family members have different forms of synaesthesia; for example, a mother with coloured letters may have a son who tastes words.

Q.10 Are women more likely to have synaesthesia than men?
This is debatable. It was once well accepted that synaesthesia was more common in women than men but recent research suggests that the female bias is smaller than once believed or perhaps even non-existent (Simner et al., in press; Ward & Simner, 2005). One problem is that men may be less likely to come forward and volunteer for research and less likely to admit to having synaesthesia. The ratio of female to male synaesthetes has important implications for genetic models of synaesthetes. It has been suggested that synaesthesia is inherited via the X chromosome (e.g. Bailey & Johnson, 1997). This means that a mother can pass synaesthesia on to either a son or daughter, but a father can only pass it on to a daughter. This may explain why synaesthesia has sometimes been shown to be more common in women.

Q.11 Do identical twins have identical synaesthesia?
No. Alford (1918) documented two male twins with letter>colour synaesthesia, and who agreed on only 67% of their colours. A second twin study (Smilek et al., 2002) reports two genetically identical females, one of whom has synaesthesia (letter-to-colour) and one who does not. Women contain two-copies of the X chromosome, only one of which may be active, and which one is active can differ between twins who are otherwise genetically identical.

Q.12 I always think of numbers/alphabet/calendar as having a particular spatial form. Is this synaesthesia?
Some people might think of numbers having a particular arrangement in space. For example, the numbers 1 to 10 may be mentally arranged on a vertical line, which turns right at 11 and then makes a 30 degree upward turn at number 50, and so on. There have been similar reports for alphabet, days and months (e.g. Cytowic, 1989; Galton, 1880). Some people consider this synaesthesia, while others consider it simply something that sometimes co-occurs with synaesthesia. ^

Q.13 I see coloured auras around people. Is this synaesthesia?
Possibly. Although some people are attracted to more mystical explanations. The colour might be triggered by the physical properties of the face, or relate to the person’s mood or character traits (Collins, 1929; Riggs & Karwoski, 1934). There are now several cases in the literature of synaesthetes who experience colours for the names of people that they personally know well (Ward, 2004; Weiss et al, 2001). 

Q.14 What is the youngest age at which it has been reported in the literature?
The youngest documented case in the literature was a three-and-a-half year old boy (Whitchurch, 1922), in whom noises produced colour (e.g. an electric fan sounded orange, and a frog bluish). We are currently examining how synaesthesia develops over time. For instance, we know that adults tend to have invariable associations (e.g., the colour of A never changes) but are children’s associations initially more variable?

Q.15 Can synaesthesia ever be lost?
A number of people have claimed that they used to experience synaesthesia but no longer do. Hence, it is possible then that synaesthesia may be much more common in preschool children than it is in adulthood. There is even some evidence to suggest that all of us are synaesthetic in the first few months of life (Maurer, 1997). Synaesthesia could also potentially be lost or diminished by chemical or organic changes in the brain (following brain injury or drug use).

Q.16 Can synaesthesia be acquired?
Yes. Hallucinogenic drugs such as LSD, magic mushrooms and mescaline can all produce transient forms of synaesthesia (e.g. Hartman & Hollister, 1963) although we are not aware of anyone who claims to have permanently acquired synaesthesia as a result of drug use. Other people have acquired synaesthesia after becoming progressively blind (e.g. Armel & Ramachandran, 1999).

Q.17 Is there a relationship between synaesthesia and artistic talent?
Some research has suggested that there might be a higher proportion of artists and poets who are synaesthetes (Dailey et al., 1997; Domino, 1989). However, non-synaesthete artists may sometimes mistake their artistic sensibilities for synaesthesia, giving rise to inaccurate estimates of synaesthesia within the artistic population. Recent studies in London however, have factored this out (Mulvenna et al., 2006) and still suggest possibly higher levels of creativity within synaesthetes. David Hockney and Vladimir Nabokov are/were synaesthetes, and many other famous artists have been put forward as potential synaesthetes (see Harrison, 2001).

Q.18 Are synaesthetes more likely to be left handed?
No. A study in London has analysed a large sample of synaesthetes on a very detailed questionnaire (50 questions) about various aspects of handedness and laterality. People with synaesthesia are just as likely to be left handed as people who do not have synaesthesia (about 10% of the each group).


NOTE: These views are the opinions of the authors and should not be taken as fact, although we have cited the relevant evidence when appropriate.

See also

Psychology Department

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Copyright (C) 2006 - 2008 The University of Edinburgh. Synaesthesia Research Group | All rights reserved. Eye image by James Collins.
06/30/08 updated.