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One problem in evaluating the effects of alcohol on behavior is that individuals have expectations about how alcohol will affect them. It is frequently believed (in our culture) that alcohol will increase sociability, reduce anxiety and tension, increase aggression, and enhance sexual responses. However, many of the effects of alcohol, especially at low doses, are due more to the individual’s expectation of effect than to the drug’s pharmacological effect (Marlatt and Rohsenow, 1980).
As you probably recall, experiments measuring drug effects have at least two groups of participants: a drug treatment group and a placebo (nondrug) group, who generally assume they are also receiving the drug. Since both groups expect to receive the drug, any difference in their scores reflects the effect of the drug alone. However, because both groups believe they are getting the drug, there is no direct measure of the extent of expectancy. A further elaboration of the research design that more specifically tests the role that expectation plays is a four-block, or 2 × 2, design (Figure 1). In this design, half the participants are told that they will get alcohol and half are told that they will get placebo. Half of each of the two groups will actually get alcohol. Thus, two groups get what they are expecting, and two groups are deceived and receive the opposite treatment.
Figure 1
To be effective, these experiments must completely deceive the participants; this includes providing the alcohol in a way that it cannot be detected, such as combining vodka and tonic and at relatively low doses. In addition, participants must be deceived about the purpose of the experiment—for instance, by being told that they are involved in a taste test of different vodkas or different tonic waters. Results from experiments using the 2 × 2 design support the hypothesis that when participants think they have received alcohol, their behavior reflects their expectations of the drug effect. For example, in one study, college students watched erotic videos showing heterosexual and homosexual activities. The low dose of alcohol administered (0.04%) did not have an effect on physiological arousal as measured by penile tumescence, but an expectancy effect occurred. The group expecting to receive alcohol showed more physical and subjective arousal than the group that did not expect to receive alcohol, regardless of whether they actually received alcohol or not (Wilson and Lawson, 1976). This seems to be a case in which a drinker’s beliefs about the effects of a drug become a self-fulfilling prophecy, and actions match expectations.
References
Marlatt, G. A., and Rohsenow, D. J. (1980). Cognitive processes in alcohol use: Expectancy and the balanced placebo design. In N. K. Mello (Ed.), Advances in Substance Abuse: Behavioral and Biological Research, pp. 159–199. Greenwich, CT: JAI.
Wilson, G. T., and Lawson, D. W. (1976). The effects of alcohol on sexual arousal in women. J. Abnorm. Psychol., 85, 489–497.