Among cults or races of synesthesiacs roll a d5 twice (shift the second roll up one if your result is doubles; 5 goes round to 1):
1 = Sight;
2 = Smell;
3 = Sound;
4 = Taste; or
5 = Touch.
… is perceived as …
1 = Sight;
2 = Smell;
3 = Sound;
4 = Taste; or
5 = Touch.
[Edit: It took me eight months to notice I had no Taste. Heh.]