This question came up in discussion at work this week...
Of all the perceptual phenomena the flesh is heir to, one of the most puzzling and insightful effects is synesthesia. This is the condition where people perceive one property when sensing something else. One common form is grapheme-color synesthesia, when the synesthete (i.e., a person with this condition) sees a letter in particular color.
The search challenge for this week is this:
Do all synesthetes see color/letter pairs consistently?
(Or, more generally, do all synesthetes of a particular kind have the same
perceptions across individuals?)
That is, if you have 10 synesthetes, will they all see the letter "a" in red? Or will there be 10 different perceptions? For instance would you see it in green, I see it in cornflower blue, while Bob sees it in yellow?