To reduce the chance of miscommunication, we should take into account the international nature of the forum. It’s difficult to describe cognitive processes, and even harder when translating into a foreign language.
I get the impression that synesthesia still isn’t well understood, but there is some evidence that synesthesia is more common in people with conditions like schizophrenia and autism.
Let’s move the discussion about whether synesthesia can be learned over to this thread though: Study: Synesthesia Can Be Learned — this thread can stay focused on sharing memorization scores. 
Thanks for the recommendation. I ordered a copy.