[vortexforgot]

I think almost everyone has associations between things of different "categories" (you can almost smell the grass if you picture yourself in a field). As a synesthete, I have both kinds of associations (synesthetic, and non-), and many lie in the spectrum between.

The strongly synesthetic associations are 1) always-on*, 2) automatic and immediate, even for novel stimuli**, and 3) consistent over time***

* You can turn your focus away from them, like focusing on a person's voice in a noisy room, but you're still aware of the noise.

** You won't experience the smell of grass looking at a photo of a field, if you've never been to a field before. But many synesthetic associations occur immediately even for new stimuli, especially if it's a simple input like sound. If it's a complex concept like someone's personality or an algorithm, they are initially in flux and solidify as understanding of the concept improves.

*** They can change very slowly over time (years)

The above is more of a personal definition from my experience, and not a clinically accepted one.