Claims like this need robust justification. A sample of five thousand (effectively divided by two of course) seems rather small, and I'd really like to know the false positive and false negative rates. I'd also like to know the number of trials per subject and their distribution as well. Sadly the journal is paywalled so I can't find out. However, quite apart of the honesty of the subjects, I can think of quite a few distorting factors that could contribute to uncertainty.