Contingent negative variation, extraversion, reaction time and drug effects

The effect of caffeine and chlordiazepoxide on contingent negative variatio n (CNV) and on reaction time (RT) was investigated in 44 healthy naive volu nteers, in relation to various psychological tests. Early C;NV is character ised by a significant interaction between drug effects and extraversion, bo redom susceptibility, disinhibition and strength of excitation. Caffeine in creased early CNV amplitude for those with high scores and decreased it at low scores. Chlordiazepoxide had the opposite effect.. Placebo effect was n egligible. At modal scores there was no appreciable difference between eith er drug and placebo. In consecutive sessions early CNV decreased. Early CNV was not correlated with RT. In contrast, there were no significant drug effects on late CNV or on RT, e ither with or without an interaction with extraversion. Late CNV showed a s trong negative correlation with RT but early CNV had a positive effect on t his relationship. RT was also negatively correlated with extraversion. Late CNV was stable over sessions. Only for early CNV the results support the hypothesis that simulation by ca ffeine would cause a CNV decrease at low scores and an increase at high sca res, whereas inhibition by chlordiazepoxide would have the opposite effect. (C) 2001 Elsevier Science Ltd. All rights reserved.