How synaesthesia grows in childhood, and dies out

Synaesthesia is well studied in adults and is thought to be a result of unusual connections created during brain development, but it has been hardly studied in children – until now.

A new study published online in Brain searched for letter-colour synaesthetes in 6-8 year old children and found not only are they relatively common, but that the condition changes as the children grow.

Synaesthesia is where the senses are crossed, so perceiving something in one sense triggers a perception in one of the other senses. The type targeted by this study was letter-colour synaesthesia where people perceive colours when they see certain letters.

Synaesthesia is known to be partly inherited and there is brain imaging evidence that people with the letter-colour type have greater number of white matter connections between brain areas known to be involved in word and colour perception.

A popular theory is that synaesthesia results from an unusual form of brain development where certain connections in the brain are not ‘cut’ or ‘pruned’ during the early months of life.

However, letter-colour synaesthesia requires that the person can read and understand letters, which usually doesn’t happen until much latter, so it is likely that there is something going on throughout the critical learning period when children begin to learn to read.

This new study, led by psychologist Julia Simner, tested over six hundred six to seven year-old children with a computerised test that showed them letters and numbers and asked them to select a colour which best fitted the character on screen.

After 10 seconds, the test was repeated. One of the hallmarks of people with letter-colour synaesthesia is that their associations remain constant, so this helped pick out who was the most consistent.

Children who did better than average on this were tested again with a surprise test at 12 months, and those who were more consistent at 12 months than the average child at 10 seconds were classified as having synaesthesia.

Using this, admittedly strict, criteria 1.3% of children had letter-colour synaesthesia and the total number of children with any form of synaesthesia is likely to be greater owing to the fact that the researchers only tested one for one type.

The study also allowed the researchers to see how synaesthesia had developed over the year. Interestingly, the synaesthetic children showed an average of 10.5 stable letter-colour associations aged 6-7 years, but 16.9 aged 7-8, suggesting that the condition is developing and growing over time.

Although not able to confirm it statistically, the study hinted that some people may actually lose synaesthesia over time.

The researchers note that in anecdotal reports adults have described synaesthesia in childhood that died out, while the reverse pattern – synaesthesia spontaneously appearing in adulthood that didn’t exist in childhood, is not reported. A further hint is that in the study, the number of children who had synaesthesia at ages six and seven outnumbered those who had it at ages seven and eight by 2.5 to 1.

Link to study.
Link to PubMed entry for same.


  1. brad
    Posted June 24, 2014 at 7:59 pm | Permalink

    “After 10 seconds, the test was repeated.” If the questions were related would not most children repeat the same answer regardless of synesthesia?

  2. Posted September 24, 2015 at 6:00 am | Permalink

    My daughter sees the number seven . It changes not only color but direction in correlation with her mood and time of day. She is four years old and has only recently shared this with me. She is consistent. The color and direction never wavers i.e. Yellow – up, blue – down , green – right. Red – left. Her moods also directly correspond with direction and color of the seven. Up is daytime and happy. Down is night and sad. Green is right and frustrated or angry and red is left and she says she doesn’t know what it feels like. She uses her thumb to show me which direction her seven is pointing .

  3. MT
    Posted October 6, 2015 at 3:13 am | Permalink

    I remember having a type of Synaesthesia when I was a kid where I would “see sounds”. I completely grew out of it by the time I was nine or ten, but I used to listen to a single cassette tape with about five tracks on it and they were all famous classical pieces. That cassette was the only one I ever wanted to listen to because I would see pinks, purples, and blues flying around in triangles and circles. During elementary school, I also remember that whenever I took that hearing frequency test, I would see a yellow triangle.

  4. Christine
    Posted October 10, 2015 at 3:23 pm | Permalink

    My youngest son, now 24, had synaesthesia where food/tastes triggered totally unrelated colours in his head. For quite a time he would eat nothing but chicken nuggets or sausages and chips, in small quantities. It was at its peak when he was 10-12 years old. Thankfully he grew out of it and now eats most things and cooks very well. He can still remember the food/colour connections and still says there was no logic at all. It may be genetic, as I have always thought the days of the week have specific colours and the thought still persists. My (unrelated) best friend at primary school had the same experience although her colours were different from mine.

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