The effects of a depressant and a stimulant drug on the contingent negative variation.

Three groups, each comprising eight subjects, were twice tested with an interval of one week: one group receiving 10 and 20 mg chlordiazepoxide, another group receiving 150 and 300 mg caffeine and a control group receiving placebo and 'no-drug' treatment. During each session the CNV was determined five times: one pre-drug and four post-drug measurements, each divided in a condition with and one without 'white noise'. Based on Eysenck's theory it was predicted that the CNV would increase after administering chlordiazepoxide and would decrease after administering caffeine. Furthermore it was expected that 'white noise' would attenuate the CNV of introverts and would enhance the CNV of extraverts. The first hypothesis was significantly verified comparing the chlordiazepoxide group with the caffeine group. However, making comparisons within groups, only the decrease between the measurement before taking caffeine and the first one after administering was significant. The second hypothesis could be supported for introverts only.