I read about a study a while back in which researchers brought in a person who had synesthesia and asked him to identify the exact colors associated with 500 di

I read about a study a while back in which researchers brought in a person who had synesthesia and asked him to identify the exact colors associated with 500 different random numbers drawn from a range of up to a million. (He did not know what numbers they were going to ask for). A year later, they brought him back, and he repeated the associations almost word for word. I guess he still could have done it with eidetic memory or a PAO-style system, but it was still pretty impressive.