Solution 1:

If you state a negative, and I disagree, I may start with "No" to contradict your statement, and then state the positive.

This is related to our general contrariness and bad manners.

Solution 2:

Language Log has a couple entries on this:

  • Yeah No

  • “Yeah no” mailbag

  • Yet another “yeah no” note

  • Yeah No in popular culture

Click through and read. There is no shortage of hypotheses.

I have my own hypothesis to add. I think a lot of people use the word no to mean but seriously…:

A: Where’d you get that jacket?

B: I mugged a leprechaun. No, I’ve had this thing for ages. I don’t really have much to wear with it, it’s so green.

This no has almost no negative connotation at all. It’s just sort of a verbal pivot point.

(Update: This use of no is described at length in Schegloff, Emanuel A., Getting Serious: Joke → Serious ‘no’, Journal of Pragmatics, 2001, vol. 33, no. 12, pp. 1947-1955. You can obtain the PDF here by filling out a little form.)

I think this no gets to be practically subconscious in some people’s speech, and I suspect yeah, no comes from that.

Solution 3:

The responses here have missed an emerging usage of autonegation that is more perplexing than what they have in mind. Here is an example from Language Log:

A:"Did you like the movie?"

B:"Yeah, no, it was great!"

I catch myself doing this all the time in spoken conversations, usually when elaborating an opinion. Fortunately, speakers who use this phrase always clarify their meaning; person B's response in the above example is unambiguous, even if not technically consistent.

Why "yeah, no" is used in such a way is a matter of speculation. My theory is that the "no" is used because the speaker is elaborating in order to defending against a potential disagreement.

Solution 4:

It depends on the context. Often people respond first with "no" without thinking, and then realize "yes" might be more appropriate. Maybe you could provide a certain context or quote in order to clarify.