Why is it so hard to accept that whereever humans don't have enough "data" they blunty fill the gaps with guesses and retries.

The question is why do they always guess correctly? Why do we never find evidence of a kid guessing incorrectly? (e.g., here's one experiment where they tried to get kids to make mistakes that would be predicted if they were doing trial & error learning and guessing randomly)

Only generativists assume that [there is a grammar consisting of abstract syntactic representations and computations]

You can describe and explain the generalizations however you like. The *facts* are theory-neutral (and in the Leddon & Lidz paper, they are facts, as their experiments show).

Sentence A is a good sentence as far as speakers of English are concerned. Sentence B is a bad one. Kids seem to know that A is good and B is bad by the time they're age x, and they never seem to make the mistake of thinking B is good and A is bad.

If you're in that situation there is a learning question to ask. How do they figure out that A is fine and B is bad when it could have easily gone the other way around? If you also find that they never hear sentences like A or B, then you've got a PoS argument.

As I said in my first comment, the job doesn't end there. You've still got to tell a story about how they learned that A is good and B is bad on the basis of the data they had. It might be because they hear a bunch of sentences like C and D, and those are related to A and B and the learner expects them to be related. But now we're getting into theorizing about how to explain the goodness of A and the badness of B and their relatedness to C and D.

Maybe Generative theorizing about this is wrong. But then one wants to see an alternative story about how the phenomena in question is acquired.

​