Effects of ethanol and promethazine on awareness of errors and judgements of performance.

Ethanol may affect detection and processing of errors in performance tasks, and thus influence the speed accuracy trade-off. In this double-blind study, 11 volunteers, (seven female, four male) took part in four sessions in which they received ethanol (Eth; mean blood alcohol concentration at 60 min: 87.3, SD: 18.4), placebo (Pla), promethazine 20mg (P20) and 30 mg (P30) in randomized order. A computerized four choice reaction time test (FCRT), other performance measures and visual analogue scales (VAS) were administered before dosing and at intervals up to 2.5h after. During the FCRT volunteers reported errors verbally. These reports were recorded together with error signals from the computer. The overall pattern of effects was as expected for Eth, with increases in errors for most tasks, and subjective drowsiness. P30 affected only the FCRT, and both P30 and P20 caused drowsiness. The number of errors made by the volunteers in the FCRT was significantly increased for both Eth (N 5.20, p 0.01) and P30 (N 3.81, p 0.01) compared to Pla (1.84) with no significant change in response speed. The proportion of errors detected was slightly but not significantly reduced (Pla 68%, Eth 63%, P30 57%). These results show that error processing is not significantly impaired by ethanol, and a reduction in awareness of errors cannot account for the increased errors which occur when performance is impaired by ethanol.