I haven't been able to shake the feeling I got when my daughter said "I think men are smarter than

[LittleBlue]

63. You will not find the answer here

Or rather, you will not find an answer that will satisfy her. Whatever gave rise to her belief, it won't be answered quickly by a blog or an anecdote.

Everyone finds their own truth about how they measure themselves to others, and it generally comes from their personal experiences. If they've seen brilliant men promoted, they'll assume as your daughter does. If they've seen brilliant women promoted, perhaps they'll assume the opposite. Or maybe they'll adhere to the belief that every group is equal.

Truth is obscured when intelligence is quantified through testing because people extrapolate meanings in these measures that don't exist. I suspect the nail polish is just competitive instincts in women that are so strong they can become unhealthy. That doesn't necessarily mean they're less intelligent. I've heard this lack of intelligence stereotype applied to men as the "dumb jock", with no evidence to suggest that athletes are any less intelligent on average.

I think your daughter's truth can only be found from experience, and perhaps introspection to examine why she believes this. Instead of beginning by overwhelming her with stats and anecdotes, start first by asking her, "what is intelligence?" Her beliefs must be fully understood before attempting to change them.