If they say no to that, it could mean they don’t know what “syllable” means so yes and no wouldn’t necessarily mean the same thing. If you said it in imperative form, “give me an example of a one syllable word,” then a response of either yes or no would have to be an example (unless they misheard the question) but then it technically doesn’t answer what the original poster asked because it’s not a question.
Why would NO be a wrong?
Because it means you were looking.
It also may make her think you’re lying. It’s better to say, “She looks alright…” or something along those lines.
I had some very clever students of English when I was teaching in Japan for a year.
One afternoon, we spent an hour learning tag-questions (which are much easier to create in Japanese, neh?)
When our time was finished, I sent my students on their way and asked, “That was fun, wasn’t it?”
One of the guys told me haltingly, “Yes. That wasn’t fun.”
I couldn’t discern whether he’d learned the lesson or not.
—G?!
The left says “yes”
and the right says “no”
I’m in between
and the more I learn
Well the less that I know
. --Dennis DeYoung (Styx)
. Borrowed Time
. Cornerstone
Taking a pragmatic perspective (within the field of Linguistics), all these questions entail something about the content of the sentences themselves or the world. Technically, the concepts at play are called presuppositions and implicatures.
Splunge!
I believe this recent idiom is constructed of a “yeah” to indicate that the speaker has heard and is considering what you have said, and a “no” to indicate that after thought he has rejected your idea, and the joke is that the close pairing of them indicates that rejecting your idea took no consideration at all, that it was so obviously a bad idea that it was pointless of you to even share it.
For instance:
“Perhaps for your anniversary, you should give your wife a crock-pot.”
“Yeah … no.”
I took a class on communication for work, and just before the test the teacher was doing a quick review for us, which we took a bit too literally. 
See, an “open-ended question” was defined for us as a question that cannot be answered with “yes” or “no”.
Teacher: “Give me an example of an open-ended question.”
Student: “Why?”
Teacher: “Is this an open-ended question?”
Class: “No.”
Teacher, now laughing: “Is this that I am about to say an open-ended question?” I think by then we were all laughing so hard she didn’t actually ask it.
It occurs to me that the original question, and the additions most like it, are essentially a ping: any reply at all answers the real question, and a lack of reply implies an answer as well.
Which reminded me of a big problem with military IFF (Identification Friend or Foe) systems. These usually use a radio set to respond if it receives a signal on a specific frequency - another vehicle broadcasts a “query”, and the friendly vehicle responds.
The problem is that, since you usually can’t get the enemy to agree to put units in their vehicles that broadcast a “hey, I’m a bad guy” signal, the system has to equate “Foe” with a lack of response. And there are dozens of reasons why a friendly unit might not respond (interference on the query, or on the response, or damage, or a blown fuse, …).
So while what one hopes for is a Good Guy/Bad Guy identification system, what one really has is a system that often identifies targets you definitely should not shoot at, and marks all the others as “maybe”.
@Santorum: With all due respect to byu.edu (is that Brigham Young University?), they’re not 100% correct. While a rhetorical question IS one “asked for a purpose other than to obtain the information the question asks”, not all such questions are rhetorical. Rhetorical questions are, as they say later in the paragraph, a statement phrased in question form. The asker of a rhetorical question is not seeking any information at all, and is instead looking to impart information, whereas someone who asks “are you asleep” usually IS looking for information.
“Could you care less?”
I’m reminded of a speaker describing the use of positives and negatives. He described how a positive is always a positive, as in, “I am hungry”. A negative is always a negative, as in, “I’m not hungry”. There are examples, also, of a double negative being a reinforced negative, as in, “I ain’t going nowhere”, or a positive, as in, “He’s not unintelligent.” However, there is no example of a double positive becoming a negative.
At that, an audience member sing-songed back at him, “Yeah, yeah”.
Okay… this is geeky, but I vaguely recall an old Dr. Who episode with set of two identical twins, one that always lied and one that always spoke the truth, and 2 doors, one that led to escape, the other to certain death. And the evil bad guy granted him one question.
The Dr. asked one of the characters: “Which door would your twin brother tell me is the escape door?”
Problem solved.
I have been trying to figure out how to use this tactic on women!
“Are you OK?”
“OK” is not strictly defined. If the answer to the question is a sobbing/crying “yes” or a straight faced “no” what do the answers mean?