Phenobarbitone and kinaesthetic after-effect

The effect of phenobarbitone (phenobarbital), predominantly a central depressant, on kinaesthetic after-effect was examined. The subjects were selected after a preliminary testing with the Maudsley Personality Inventory. They were classified into two groups: extraverts and introverts. The drug was used at different dose levels. A 2 × 4 randomized block design was replicated ten times. The study supports the following conclusions: (a) the extraverted subjects show larger kinaesthetic after-effect than introverted subjects under placebo condition; (b) phenobarbitone has no effect on kinaesthetic after-effects in extraverted subjects except in small doses (30 mg) which reduce the size of the effect; (c) the drug in larger doses (60 mg and 100 rng) produces a significant increasing effect in the introverted group.