[bOR_]

I understood that people were asked beforehand about their beliefs. Afterwards would indeed be silly, and I would have been very surprised if 60 years of peer review would not have caught that.

Just checked the two links I pasted earlier. The second link (skeptics dictionary) quotes:

    The expression dates back to 1942 and Gertrude Schmeidler, 
    a professor of psychology at City University of New York. She 
    asked her students whether they believed in psi *before* 
    giving them an ESP card test. 

So your explanation doesn't hold here. People were asked first, and then tested.

[xiaoma]

Has this result been replicable over the past 60 years?

[bOR_]

Many times, apparently (see recent articles). There's just no explanation except fraud or misformed experiments that fits well with our current scientific understanding of the world, and those shouldn't be invoked just to keep your comfortable world-image :).