I was therefore interested to read some of the links that beatnikbetty posted on the topic, particularly these two scenarios, as it seems an excellent example of this subtly different way of viewing situations.
When going through them, without hesitation I went for the standard non-aspergers answers as they seemed obvious. It was only reading through the brief discussion afterwards that I started to see why people might go for the other option.
One day I may go and learn some psychology, as it's always seemed a curious subject, but alas too many things are.
EDIT Given the comments it seems worth explaining my reasoning in choosing my responses:
The way I thought of it was that the second case was intentional as he had to make a concious decision as to whether to pay the extra dollar and get the drink or whether not to and not take the drink (or go for a smaller one). In the first scenario he pays the same amount and gets the same product, just gets an extra cup thrown in (which presumably he can just leave behind if he really doesn't want it). The cup doesn't have the same role in the decision process as the dollar.
That said it does seem a bit overly simplistic to diagnose Aspergers entirely on 2 questions like that. The fact that Aspergers people have a tendency to say one thing and non-Aspergers people have a tendency to say something different (as they are stating the research shows) doesn't necessarily mean that someone who comes up with one a particular answers falls into the corresponding group.