Who did you know looks like Bill? (know=realize)

[Seiichi Myoga]

My question is based on (1) (Could you please let us know if you think (1) is actually wrong).

(1) Who did you realize looks like Bill?
(M. Hegarty, "Adjunct Extraction without Traces")

How about (2a) and (2b)?

(2) a. Who did you know looks like Bill?
b. Who did you know that looks like Bill?

I think (2a) is wrong (unacceptable) but (2b) is OK.
Do you agree?

I hope as many native speakers of English as possible help us, especially, with the judgment of (2a).

Thank you in advance
Seiichi MYOGA

[Clunker]

(A non-native speaker's tentative answer):

Only Who did you know that looks like Bill? is unacceptable because who is subject of the nominal that clause. that must be omitted to prevent it being initially misinterpreted as subject of the following verb.
Compare the following optional that,

Who do you expect (that) they have chosen? (who is object in the nominal that clause)
She told me how she thought (that) the machine worked. (how is adverbial in the nominal that clause)

[Seiichi Myoga]

Hi Clunker,

I had expected to hear from a native speaker of English, but thank you all the same.

It is generally known that we can't extract something from the subject position in a smaller clause when there is a complementizer (like "that"). So, delete "that" and (3) will be fine.

(3) Who do you think (*that) was chosen?

As for (2b), "who" comes from the object position of "know" but not from the subject position of "looks." In other words, the "that" clause is a relative clause modifying "who" and not the object noun clause of "know."

It's difficult to think of an example sentence where "know" means "recognize," but if it works in (2a), I'm wondering if (2a) is acceptable or not. The reason: when "know" works as a "bridge verb," there seems to be a restriction on its meanings. And I'm assuming that English-speaking people will disapprove of (2a). But I'm not sure. That's why I posted this thread here.

Seiichi MYOGA

[Clunker]

[Seiichi Myoga]

Clunker,
Just because the syntax is the same doesn't mean that the two sentecens are acceptable.

The content of a smaller clause can affect the acceptability of a sentence.

(3) Who do you regret [could not make it /? stole the file]?
(M. Hegarty, "Adjunct Extraction without Traces")

And in the first place, attention must be paid to verb types: verbs like "know" and "regret" are factive verbs, but "think" is not.

(4) a. Do you know who married John?
b. *Who do you know married John?

(4b) is just not acceptable.

Seiichi MYOGA