The balanced placebo design: effects of alcohol and beverage instructions cannot be independently assessed

Abstract

Subjects were randomly assigned to the four cells of the balanced placebo design, with 10 males and 10 females per cell. Following told-alcohol or told-no alcohol beverage instruction manipulations, participants consumed either a vodka-tonic beverage containing a dose of vodka sufficient to induce a peak blood alcohol level of 0.05% or a beverage containing only tonic water. Subjects' self-report ratings of beverage alcohol content indicated that alcohol overrode the effects of beverage instructions in the told-tonic/given-alcohol condition. It was concluded that the design cannot independently evaluate effects of both alcohol and beverage instructions when behaviorally significant alcohol doses are administered.