I've just watched this and read some background. Apparently the uncle's character was inspired by a real-life serial murderer in the '20s, who was alleged to have attempted to molest a young girl. Not sure if Hitchcock did this on purpose but it's a creepier angle to consider.

I agreeI think the detective was able to coerce her thinking in a certain way.
If you're not taking any steps forward, you're not moving at all.

I always thought Anne didn't like Uncle Charlie for 2 reasons. First, I agree Anne is very smart, and seemed to be able to read people well. But secondly, if you remember towards the end of the film, she has made "friends" with the detectives, particularly Mr. Saunders. They obviously were talking to Anne, trying to find out information about Uncle Charlie. I think she put 2 + 2 together, and realized that men asking questions about her Uncle, who she already doesn't really like, means there's something off about Uncle Charlie.

I agree with many of the other posters, kids are just smarter, they recognize evil easier than other people do, even if they aren't aware of it, they know when they don't like somebody, even if they don't have an actual reason to, it usually turns out there's a good reason not to like them.

I also think that Ann may have felt animosity towards Uncle Charlie because his arrival forced her to change her daily routine. She didn't have the strong bond with Uncle Charlie that young Charlie did because of her age. To Ann he was just a stranger forcing her to share a room with her older sister.

Then that must be why they tell you to consult a third-grader when you purchase some new technology because they're the only ones who could figure out how to open a child-proof aspirin bottle.
Same goes for the kid on "Good Times," the daughters on "Full House" and Jimmy Carter's little girl, Amy, and every presidential child since. They have to be the adults in the room because, well, somebody has to be, I suppose.

I was wondering the same thing. Maybe she just sensed he was no good.

She's a reader, I assume she read her dads paper.
Only those with no valid argument pick holes in people's spelling and grammar.

I agree with the other posters. She was an old soul, inquisitive and a thinker. Her instincts were correct.

Children are known to be acute in their senses. Ann might have known something was up.
When theres no more room in Hollywood, remakes shall walk the Earth.

Ann's the sharpest member of the family, and follows her gut instincts about Uncle Charlie.
I'm not crying, you fool, I'm laughing!
Hewwo.

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