The difference between Gouzalis May Frank 2000 study is that it was a comparison study between ecstasy, cannabis, and those who don't use drugs. Zakzanis's study tested MDMA users memories and then retested them a year later. The results were that the amount of MDMA tablets used went up roughly by four tablets. Also, the scores from the memory tests (recalling details from a short story) declined.

The use of a Longitudinal study (Zakzanis) is more convincing than a simple comparison study (Gouzoulis) because it tracked the same person and recorded data as time went on.

Memory: longitudinal data (Zakzanis)