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Yes, wandered off the topic again. Anyway, I'm sure the Tuskens may get bold enough on occasion to approach Ben's house and he probably has performed some Jedi tricks on them to keep them away, especially at night when he's sleeping. So, in a way, while the Tuskens may not actually be scared of him, they may just be wary and test him once in a while.
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He certainly must have quite a large knowledge of them after what he says about them by the sandcrawler "Sand people always walk in single-file to hide their numbers." I think that during his time on Tatooine he might of spied on them to learn about them. After all, there wasn't much else to do there. It must of got pretty boring for the poor old guy.