Quote Originally Posted by TinCow View Post
The paragraph you altered seems like something that would only be encountered in someone who had suffered damage to the language section of the brain, not something that would ever be encountered in an otherwise normal person.
Very true. You're really only ever going to run into that kind of serious grammatical deficiency in people who never learned a first language (deaf people not exposed to signing until teenagers or later, abused children isolated until the same age), people who've suffered strokes or otherwise damaged the language-related parts of the brain, and people with (probably heritable) language impairments.

What I was imagining were the numerous grammatical errors which are common in people who are still in the early phases of learning or who have otherwise not learned the language properly.
I know what you mean here, but I'd argue that those aren't errors, but features of non-standard dialects/ideolects. When it comes to language, the early phases of learning are 1.5 to 2.5 years. By 3 years old, the grammar is pretty much known. Rules that have to be drilled later are not a part of the language itself, but artificial add-ons. Of course, that doesn't mean it's not important to observe them in certain social settings, because a lot of how we judge people depends on whether they've learned those little add-ons.

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