"who" vs. "that"

[Bill Palmer]

A current Kellogg's Special K commercial claims, "Research shows women THAT eat breakfast have fewer problems with weight" (last few words may not be exactly right, but you get the picture)

I would have said "...women WHO...", because it just sounds more natural.  Are there any "prescriptions" for this?

Bill Palmer

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The American Dialect Society - http://www.americandialect.org