This may be more work than you're asking for, but you could send a survey out to okps asking them about certain people, whether they think they're white or black or another ethnicity, and why they think they are that ethnicity. The people you choose to be guessed could self-report their ethnicity, or you could know their ethnicity already (though that may bias the study).

It just BES that way sometimes.

Yabbadabbadoozilla! (c) Bootzilla
http://www.funkknots.com
http://www.cartoonista.com
http://www.pocho.com

"Men lied about that ---
Some of them cried about that ---
Some of them died about that ---
But everything fightin' about a spoonful
That spoon, that spoon, that ---
It could be a spoonful of water
Saved me from the desert sand
But one spoon of them forty-five
Saved you from another man" -Howling Wolf

"You might as well pay attention/ you can't afford free speech" -George Clinton

"People need to stop saying that there is one way to be--and then the issue will disappear." Ntozake Shange-interview in _Mother_ _Jones_