My grandmother told me a story about when my dad was in school. He took an exam in first grade where there were basic questions and you had to circle the right answer. Typical little kid stuff, except that one of the questions was, “Which woman is prettier?” and the choices were a tall, thin blonde or a short, fat brunette.
That was the only question that my dad got “wrong”. His grade was lowered because he didn’t believe that there was only one kind of “pretty.”
(My grandmother descended on the teacher like a rabid wolverine from hell over that test. That’s why she still remembered it 40 years later. And even today, my dad still knows that my short and fat mom is pretty.)
Thin privilege is being the “correct” answer to the question of “which woman is prettier?”