You explain that the participant have to make 2 choices.
The participant then have to choose between 2 bags A or B. After the participant has chosen one of the bags, he must now make his second choice. Which decides whether he should smash the bag he just chose or whether he should smash the opposite bag. And after you have explained choice number 2 you tell the participant that he can change his first choice if he wants. it’s entirely up to him!
The participant have 100% free choice all the time!
Once the participant has made the 2 choices. he must smash one of the bags! Which turns out to be empty…
Afterwards you ask the participant to take the contents out of the opposite bag, which turns out to be a large nail!
simple routine with gaping reactions!
The 2 choices the participant have to make!