I would like native speakers of English to tell me where they'd place the nucleus/focus/tonicity of these sentences. (Mind you, most of these sentences are out of context here!)
1. How languages are learned.
2. Will you take this one | or that one?
3. (looking at a multiple choice exercise) You've chosen the wrong one.
4. (A: Take that jacket!) B: Which one?
5. Is that the only one?
6. Where does the nucleus go?
7. Where does the fall-rise fall?
8. The baby-girl arrived.
Is there any difference in nucleus placement between "boyfriend" as the person somebody's dating, and a male friend?
Stress is important mainly in individual words, not complete utterances.
Boyfriend is only stressed one way (BOYfriend), no matter what the intended meaning.
In multisyllabic words in your examples, the stress is on the first syllable in every word except "arrived," which is stressed on the second syllable.
Francisco, stress in complete utterances can make a subtle difference in the meaning. In some of the examples you gave, you could stress different words:
Is that the ONLY one?
Is THAT the only one?
(You can make up different scenarios in which each emphasis would make sense.)
Where does the NUCLEUS go?
Where DOES the nucleus go?
(The latter example is a pretty common occurrence. One person will ask a question: "What are we gonna DO, sarge?" and another person will say, "Yeah, what ARE we gonna do, sarge?"
(Does anyone recognize the source of that little bit of dialogue?)
<< Is there any difference in nucleus placement between "boyfriend" as the person somebody's dating, and a male friend? >>
<< Boyfriend is only stressed one way (BOYfriend), no matter what the intended meaning >>
That's right. You might hear someone emphatically separate the two parts of the word and give them equal stress, as if they were two words -- "boy...friend" -- to emphasize the difference, but that's not the actual pronunciation of the word "boyfriend".
Deborah, with her examples, beautifully demonstrates how wrong Mxsmanic is here. Stress is very important in complete sentences. Where to put it depends on your meaning.
"Stress is important mainly in individual words, not complete utterances."
??! That is completely untrue. Stress differences in the context of an overall utterance can carry significantly different meanings. Francisco, it's hard to say where I'd put the nucleus on a lot of those utterances because of the lack of context.
"3. (looking at a multiple choice exercise) You've chosen the wrong one."
In that context I'd give the primary stress to "one" (I also would say "You chose the wrong one" in that case, but that's another subject entirely and doesn't affect the stress).
"4. (A: Take that jacket!) B: Which one?"
This one depends. If it's the first time I'm asking which one it is, I'd say "one" gets the stress. If I'm annoyed at person A telling me to take the jacket over and over, I very well might try to end things by saying "WHICH one?"
The stress Deborah describes is pretty much universal, not unique to English, and not part of English. Most people will naturally stress the elements of an utterance that to them carry the most important meaning at the moment of speaking, but this isn't something governed by the language they are speaking.
The only English-specific stress is that within words, which normally stays constant independently of any other stress used within an utterance. The stress within a word can be phonemic in English.