Cathleen O’Grady, in Ars Technica:
A recent paper in PLOS ONE suggests that the letter-color pairings of many GC synesthetes might have been conditioned by objects in their environment as children, such as colorful alphabet fridge magnets. The researchers are clear that they’re not suggesting that synesthesia can be learned, or that colorful letter toys lead to synesthesia. Rather, their results simply show that the associations can be influenced by their environments. Knowing this can shed light on some of the mysteries about the condition.
The data came from the Synesthesia Battery, a site where people who suspect they have synesthesia can explore their condition in exchange for providing research data. The tests on the site verify that participants are synesthetic by checking whether their letter-color matches are consistent, and whether they take longer to process letters that aren’t in the “correct” color.
Using data from 6,588 people, the researchers worked out which colors were most commonly associated with which letters. They found that their results were consistent with previous experiments showing that English speakers often have possible spelling-based associations. For example, “G” is commonly green, while “Y” is commonly yellow—tendencies that can be found in the trends present in large collections of synesthetes.
I’ve long suspected that fridge magnets may have contributed to my strong color association with letters and numbers. But there are different kinds of synesthesia, and there may be no explanation, other than wiring, why letters also have sexes, and numbers and months have spatial positions.