Before reading the studies, we did this exercise in my Experimental Econ class a couple years ago. However, beforehand the teacher didn't let any of us know P=0 even though it should have been obvious.

We did the test 4 times in a row.

There were 12 students in my class (an upper division econ class at a private school)

Test 1: I guessed 20 (answer was 22, I was closest)

Test 2: I guessed 12 (got it exactly)

Test 3: I guessed 7 (split the reward with one other student)

Test 4: I guessed 3 and the answer was 2

If more tests were done I could only assume the whole class would have eventually gone to 0.

When reading the paper it amazed me how many people put 0 as the answer on single trials. Yes, P=0 but a lot of people don't know that (the study was done by advertising a monetary award in the newspaper) and even more may know that and still guess what others will put.

The logical way to look at the test is breaking it down into what level you think people will guess on.

Level 1: everyone guesses 100 so guess 66.66

Level 2: What idiot would guess 100, everyone guesses ~67 so guess 2/3*66.66 = 44.44

Level 3: But everyone will think ~44 so guess ~30

Level 4: Guess 30*2/3= ~20 and so on