I've been wondering for a while where the boundary for being diagnosed with synaesthesia is - nearly everyone I know has some sort of synaesthesia, even if it's only associating numbers with colors. Yet, it's no where near the viewing-numbers-as-landscapes of Daniel Tammet's Born on a Blue Day or Nabokov's gift with words.
I suspect almost everyone has a little synaesthesia, just like almost everyone has a little depression, a little anxiety, a little Borderline Personality, a little schizophrenia...
I guess it's only worth giving your mental quirks a name if, say, they're 2σ above norm. I dunno, ask your doctor (or statistician :P).
