Do You Have Asperger's Syndrome?

How do we think about the intentional nature of actions? And how do people with an impaired mindreading capacity think about it?

Consider the following probes:

The Free-Cup Case
Joe was feeling quite dehydrated, so he stopped by the local smoothie shop to buy the largest sized drink available. Before ordering, the cashier told him that if he bought a Mega-Sized Smoothie he would get it in a special commemorative cup. Joe replied, ‘I don't care about a commemorative cup, I just want the biggest smoothie you have.' Sure enough, Joe received the Mega-Sized Smoothie in a commemorative cup. Did Joe intentionally obtain the commemorative cup?

The Extra-Dollar Case
Joe was feeling quite dehydrated, so he stopped by the local smoothie shop to buy the largest sized drink available. Before ordering, the cashier told him that the Mega-Sized Smoothies were now one dollar more than they used to be. Joe replied, ‘I don't care if I have to pay one dollar more, I just want the biggest smoothie you have.' Sure enough, Joe received the Mega-Sized Smoothie and paid one dollar more for it. Did Joe intentionally pay one dollar more?

You surely think that paying an extra dollar was intentional, while getting the commemorative cup was not. So do most people (Machery, 2008).

But Tiziana Zalla and I have found that if you had Asperger Syndrome, a mild form of autism, your judgments would be very different: You would judge that paying an extra-dollar was not intentional, just like getting the commemorative cup (Zalla and Machery ms).

Why is that? Why do people with Asperger Syndrome understand intentional actions differently from people without this syndrome?