Someone shared a photo of those colored wooden rods which were used to teach maths in primary schools in WA in the 1970s on Facebook. These ones had colours that were faded and drab compared to most photos of Cuisenaire Rods which can be found on the internet. Perhaps the rods that they provided for young students in WA schools faded with age or after being washed. I was quite amazed to see that six out of the ten digits represented by the rods in the WA photo were in colours that roughly correspond to my colour-grapheme synaesthesia for numbers. One of the rod colours was pretty close. I don’t think this is a coincidence. One of the numbers that was not a match for the rods in colour was indeed a match for the old Australian paper dollar note for that number.
Does finding a learned origin for my synaesthesia associations show that my synaesthesia is not “biological” or genuine? No it doesn’t. Synaesthesia researchers know that syn is a thing that develops at around the age when kids are being educated with tools such as these rods, and it is known that there are cultural/linguistic influences on grapheme-color synesthesia.
This is a link to some Cuisenaire Rods for sale. The colours are a bit different to the ones I used as a kid: