Hello Donnach,
First to correct myself in this part you've quoted from my previous post,and sorry if I've misled you with it.Correct would be "The head of a noun phrase is(virtualy always): (if it is) premodified with an adjective or/and noun and (if it is) postmodified with a relative clause,prepositional phrase or/and a non-finite clause.(I've painted red the part I missed to enumerate.It is generally all that you can use if you want to change in any way the meaning of any noun.(Although there are some minor type of modification of nouns).And again to emphasize what is important about the quoted part: Relative clause modifies a NOUN.The words which connect i.e glue relative clause to a noun are:Relative pronouns- who,which and that,and relative adverbs - when and where (rarely also "whom","whose"and "why" do that job but forget about it and stick to the major players).That words ,most often,immediately follow the noun which they modify,but sometimes some other phrases or clauses intervene in between the noun and a relative word.Now let's move to your latest post.
This part in your post is not adequate:"a noun clause by definition includes all its modifiers".Let the term "modifier" asocciate you to a phrase and say "NOUN PHRASE by definition includes all its modifiers".I would use the term "modifier"only for words,phrases or clauses which modify nouns,adjectives or adverbs.Forget about the "modifiers of clauses".Let me remind you of the distinction between a clause and a phrase.Clause is a sentence on its own,only it is subordinated or coordinated to some other clause.A complete thought (= total clause) we call a sentence and it is often consisted of a whole mesh of subordinated and coordinated clauses of a lower level. The analysis of any clause is absolutely the same thing as an analysis of the whole sentence.In other words,when you analyse structure of a sentence or clause,use only following terms to avoid confusion:
Subject,Verb,Direct object,Indirect Object,Prepositional Object,Subject Complement,Object Complement and Adverbial.
Which means that a noun clause and any other clause by definition may include only some of this parts.You've correctly identified that the direct object of the original sentence("that children have a built-in mechanism, which he called the Language Acquisition Device, or LAD, which pre-programs them to develop grammar based on the linguistic input they receive"),is a noun("that")clause.But,since it is a clause we speak in terms which I've enumerated above,i.e. this clause includes: subject,verb and direct object.So,the direct object of the whole sentence has in its structure its own direct object and it is :"a built-in mechanism, which he called the Language Acquisition Device, or LAD, which pre-programs them to develop grammar based on the linguistic input they receive".And this direct object unlike its higher counterpart is a phrase,not a clause.That means,use only the following terms and no other when speaking of phrases(forget about articles and other determiners for now,although they are also included in a phrase):
Pre-modifier , Head , Post-modifier
built-in , mechanism ,relative clause 1, relative clause 2
In this phrase the connection between the clause 2 "which pre-programs them to develop grammar based on the linguistic input they receive" and the "mechanism" which it modifies, is blurred with presence of intervening clause 1 "which he called the Language Acquisition Device, or LAD" which also modifies the same noun "mechanism".In this phrase the two "which" relative clauses are on the same stand i.e ,along with "built-in" they are the modifiers of "mechanism".Putting it in the same basket with elliptical 'that'clause- they receive,and the past-participial phrase based...input, is a major mistake.Those are not of the same kind as the former two relative clauses,i.e they don't modify mechanism".Those are only parts of the relative clause2 which does modify "mechanism".
As a conclusion,what I see as baffling for you is that you can't accept a relative clause as a single modifier of a noun.Let me illustrate my point by comparing following two sentences:
1. I've bought a ruined house. vs 2. I've bought a house which is in a bad condition.
Maybe you will feel that "ruined" is too strong an expression and you will choose "which is in a bad condition".It only depends on how you want to put it.The point is that nobody forces you to use one single word to describe or tell something more about that house.
Although oversized,bulking,ungainly - relative clause is one postmodifying element of a noun.And what you are trying to do is to chop the relative clauses in a sentence,pick a word or part from it and then relate that part separately to the noun or some other parts of the whole sentence.Simple rule:After you've found that some clause is a relative clause i.e that it refers back to some noun,always interpret that relative clause as a single unseparable unit and don't relate some parts of it to that noun which the whole relative clause modify.If you do that,for the answer you will get nothing,except a confusion,of course.
And if we put it generally: A clause can be part of a phrase,and a phrase can be part of a clause.It is a reciprocal relation.
I did my best Donna this time.This issue certainly entails a lot of things but they are not difficult at all, only it seems that I just can't present it in a simple and a concise way.It is maybe the easiest way to identify, when reading some text,every case of "refering back" to a noun like:
The boy that is playing...
The place where I lived..
The girl who spoke to him..
The year when I graduated...
The mechanism which pre-programs them...
The linguistics input (that) they receive.. and so on..
All the best,
Velimir
. Just a regular grammar enthusiast.