tokens: Fifteen polydrug ecstasy users and 15 polydrug non - ecstasy user controls completed a general drug use questionnaire , the Brixton Spatial Anticipation task ( set shifting ), Backward Digit Span procedure ( memory updating ), Inhibition of Return ( inhibition ), an emotional intelligence scale , the Tromso Social Intelligence Scale and the Dysexecutive Questionnaire ( DEX ). Compared with MDMA - free polydrug controls , MDMA polydrug users showed impairments in set shifting and memory updating , and also in social and emotional judgement processes .