INTERACTION BETWEEN EXTROVERSION AND DRUG-INDUCED CONDITIONS AS INDICATED BY THE CONTINGENT NEGATIVE-VARIATION

The effects of chlordiazepoxide, caffeine and placebo on the contingen t negative variation (CNV) in relation to extraversion were investigat ed in a double-blind study. Forty-four healthy naive volunteers, varyi ng in extraversion scores, took part in the study. The baseline values of the O wave, E wave and average CNV amplitudes decreased significan tly in successive experiments for individual subjects. Administration of the drugs caused a change in the amplitude of the O wave from basel ine, whereas placebo effects were negligible. For chlordiazepoxide the change was positive at the lower end of the extraversion score and ne gative at the upper end, while for caffeine the opposite was found. Fo r the individual drugs the correlations with the change in O wave and extraversion score were not significant (P < 0.20 in the case of both drugs). Analysis of the difference in the effect on O wave between the drug and the placebo yielded a significant negative correlation for c hlordiazepoxide (P ( 0.05) whereas the positive correlation for caffei ne was not significant (P < 0.40). The individual differences between the effects of chlordiazepoxide and caffeine on O wave correlated sign ificantly with the extraversion score (P < 0.02). This difference was positive at the lower end of the extraversion score and negative at th e upper end. The same trend was found in the case of E wave and averag e amplitude but not significantly so. This finding supports the hypoth esis that CNV is an indicator of the interaction between extraversion and condition.