Psychopharmacological effects of alcohol on time perception: the extended balanced placebo design.

Time perception is affected by the pharmacological action of many drugs, but the contribution of expected effects of drugs has not been considered. A new design, the extended balanced placebo design (EBPD), is presented to study both the pharmacological and expected effects of alcohol on time perception. The EBPD makes it possible to examine the effects of alcohol across a broad range of expected and pharmacological doses. By contrast, the domain of inquiry was limited to low doses of alcohol in the original balanced placebo design. The design was later modified to study higher doses, but the control and the pure drug and expectancy conditions were sacrificed in the transformation. In the EBPD, however, any realistic combination of the expected and actual dose of alcohol can be studied, while retaining pure drug and expectancy conditions. The EBPD was tested in the present study with respect to its psychopharmacological effectiveness and the effects of alcohol on time perception. The design was effective in terms of three manipulation checks: blood alcohol concentration, subjective intoxication and postexperimental beliefs about the alcohol content of the beverage consumed. In addition, the expected and actual doses of alcohol interacted over time to evidence active compensation for the pharmacological effects of alcohol on time perception. Finally, a covariance structure model was confirmed in which the expected and actual doses of alcohol increased the perceived rate of time passage, which in turn lengthened objective estimation of a one-second interval.