Amphetamine (AMP) improves true memory for studied words, while THC impairs it, but neither drug significantly changes the tendency to falsely remember nonstudied words compared to placebo. Across participants, the drugs' effects on true memory correlated positively with their effects on false memory, suggesting that encoding processes influenced by these drugs similarly affect both accurate and false recollection. These results come from two within-subjects, double-blind experiments using the Deese/Roediger–McDermott illusion to test recognition memory two days after drug administration.
Both MDMA and methamphetamine increase feelings of connectedness during casual conversations with an unfamiliar partner, and both drugs raise oxytocin levels. However, only after MDMA are oxytocin levels linked to feeling closer to the partner. The study involved 18 participants given MDMA or placebo and 19 given methamphetamine or placebo. These results reveal a new aspect of MDMA's pro-social effects and show that methamphetamine produces a similar behavioral effect, though through a different biological pathway.