Little kids make such cute mistakes when they talk. We know they’re still learning the language, so we tolerate their errors and chuckle at how funny they sound. Behind that chuckle is the assumption that the kids are getting it wrong because they just don’t know the rules yet. In fact, kids’ mistakes show they know a lot more about the rules than we think. The mistakes are evidence of very smart hypotheses the kids are forming from the limited data they’ve been given so far. Here are 10 really smart language mistakes that kids make.