Now I'm really confused.
Next time I go to the fish and chip shop and they ask me if I want salt and sauce on my fish supper (or salt and vinegar if I'm below the border), what should I say ?
That's a prime example, they're waiting to see whether you say 'yes' or 'aye'. An answer of aye and you get haddock, yes for cod. Of course if your accent's broad enough it'll be a mars bar instead so you have to be careful.
Hope that's cleared it up.
Nick