Effects of diazepam and methylphenidate on the electrodermal detection of guilty knowledge.

S i x t y male undergraduate students p a r t i c i p a t e d i n an experiment designed to i n v e s t i g a t e the e f f e c t s of a n t i a n x i e t y and s t i m u l a n t drugs on p o l y g r a p h i c i n t e r r o g a t i o n . Subjects were randomly a s s i g n e d to one of four groups. Three of the groups watched a 12 minute videotape d e p i c t i n g the b u r g l a r y of an apartment through the eyes of the t h i e f . Each s u b j e c t was asked to imagine that i t was he who was committing the crime and was given i n s t r u c t i o n s to encourage h i s becoming absorbed i n the videotape. Afterwards, they were accused of commiting t h i s crime. Each subject r e c e i v e d one of three l o o k a l i k e c a p s u l e s c o n t a i n i n g a drug which, they were t o l d , would h e l p them to escape d e t e c t i o n . Capsules f o r the f i r s t group c o n t a i n e d 10 mg of diazepam; those f o r the second group, 20 mg of methylphenidate; a placebo was given to the t h i r d group. S u b j e c t s i n the f o u r t h group, the innocent c o n t r o l c o n d i t i o n , viewed a 10 minute videotape sequence showing the i n t e r i o r of another apartment, t h i s time with no crime committed. They d i d not r e c e i v e any medication or placebo a f t e r they were accused of committing the crime. A f t e r a one hour wait, a l l s u b j e c t s were i n t e r r o g a t e d by the experimenter, who was b l i n d to both t h e i r g u i l t or innocence and drug s t a t u s . Skin conductance, heart r a t e and r e s p i r a t i o n were monitored; a l l c h a r t s were scored b l i n d l y . No drug e f f e c t s were found i n the g u i l t / i n n o c e n c e c l a s s i f i c a t i o n or i n any of the p h y s i o l o g i c a l channels