MEMORY DISTORTIONS : Alcohol Placebos Influence the Misinformation Effect Seema

Can the simple suggestion that you have consumed alcohol affect your memory for an event? Alcohol placebos affect social behaviors but not nonsocial ones, and have not previously been shown to affect memory. We investigated the effect of alcohol placebos using materials that revealed both the social and the nonsocial influences of memory. Subjects drank plain tonic water, but half were told it was a vodka and tonic; then all subjects took part in an eyewitness memory experiment. Subjects who were told they drank alcohol were more swayed by misleading postevent information than were those who were told they drank tonic water, and were also more confident about the accuracy of their responses. Our results show that the mere suggestion of alcohol consumption may make subjects more susceptible to misleading information and inappropriately confident. These results also provide additional confirmation that eyewitness memory is influenced by both nonsocial and social factors. Many people believe that drinking alcohol affects their ability to remember events. In fact, some people who have committed violent crimes while drunk claim to have no memory of the crimes (Swihart, Yuille, & Porter, 1999). Although some of these offenders may be lying, Swihart et al. suggested that for others, memory lapses might be a state-dependent memory effect: A man who assaults his partner while drunk does not remember hitting her once he is sober. In the study we report here, we investigated how people’s memories are affected when they have not consumed alcohol, but simply are told that they have. Research shows that the mere suggestion that one is drinking alcohol can influence a wide range of dependent measures (Hull & Bond, 1986; Marlatt & Rohsenow, 1980). For example, when subjects receive an alcohol placebo, they become more aggressive (Lang, Goeckner, Adesso, & Marlatt, 1975), interested in violent and erotic material (Lansky & Wilson, 1981; Wilson & Lawson, 1976), and sexually aroused (George & Marlatt, 1986), even though their beverage contains nothing more than plain tonic. The pioneering procedure in this line of research is known as the balanced placebo design (Marlatt & Rohsenow, 1980). In this design, subjects are told either that they are drinking alcoholic beverages or that they are drinking nonalcoholic beverages, and what they are told is either true or false. This 2 2 design separates the physiological and psychological effects of alcohol on a dependent measure. Interestingly, Hull and Bond’s (1986) meta-analysis showed that there is no interaction between the physiological and psychological effects of alcohol on memory; they concluded that researchers can run only half of the design, depending on their research question. As cognitive psychologists, we were interested in only the effects of alcohol placebos on memory; therefore, we ran the half of the balanced placebo design manipulating expected drink content, but served all subjects a nonalcoholic beverage. Although alcohol placebos have produced significant changes in social behaviors, they have not produced similar changes in nonsocial behaviors—those not thought of as being socially constrained, or in the sphere of social influence, such as reaction time, memory for word lists, and performance on general knowledge tests (Hull & Bond, 1986; Maylor & Rabbitt, 1993; Nelson, McSpadden, Fromme, & Marlatt, 1986). Why are only social behaviors affected by alcohol placebos? Research suggests that alcohol provides an excuse for people to engage in desired—but socially inhibited—behaviors, and then explain them away (Marlatt & Rohsenow, 1980). Of course, Hull and Bond (1986) showed that these effects are not limited to “relatively deviant social behaviors” (p. 347), but can extend to any behavior that people may normally keep in check (e.g., outbursts of laughter; Vuchinich, Tucker, & Sobell, 1979). Memory performance is not typically described as something kept in check; perhaps unsurprisingly, then, there has been no successful demonstration of alcohol-placebo effects on memory. We believe that previous investigations of alcohol placebos and memory have not used materials that would reveal the social influences of alcohol on memory. However, the classic eyewitness memory paradigm (Loftus, Miller, & Burns, 1978) incorporates both nonsocial and social factors, and is thus an ideal method by which to study the effects of alcohol placebos on memory. In this procedure, subjects first view slides depicting a simulated crime, then read a narrative of the event riddled with misinformation, and finally are asked what they remember about the original event. Hundreds of experiments have shown that it is easy to distort people’s memory of an event (Frost, 2000; Lindsay, 1990; Loftus et al., 1978). The question we asked was whether subjects who are told that they are consuming alcohol are more prone to the misinformation effect (Belli, 1989) than subjects who are told that they are consuming a nonalcoholic drink. This question turns on the extent to which the misinformation effect has a social component. Certainly, the effect has a cognitive component, which involves performance on control items: Subjects base their answers on what they can remember from the slide sequence and report this information on the memory test. On what do subjects base their test answers for items about which they have been misled? Research suggests that there are social factors affecting performance in the face of misleading information. For example, the misinformation effect can vary depending on the status of the person who provides the misinformation. Dodd and Bradshaw (1980) showed that the impact of misleading postevent information (PEI) varied with the credibility of the “misinformation messenger.” Subjects were more influenced by misleading PEI when it was supposedly written by a neutral source than when it was written by a defense lawyer. In another study, when subjects heard spoken PEI, only those who rated the speaker high on a scale of power and attractiveness tended to be misled; those who rated the same speaker low on those dimensions were unaffected by PEI (Vornik, Sharman, & Garry, in press). Finally, for the misinformation effect to occur, at some point subjects must capitulate to the misleading information, Address correspondence to Maryanne Garry, School of Psychology, Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand; e-mail: [email protected]. PSYCHOLOGICAL SCIENCE Alcohol Placebos and Misinformation 78 VOL. 14, NO. 1, JANUARY 2003 which is provided by another person. Thus, social factors do affect the extent to which people are misled even when they do not receive the suggestion that they are drinking alcohol. In the current research, we combined two classic experimental paradigms: half the balanced placebo design (Marlatt & Rohsenow, 1980) and an eyewitness testimony design (Loftus et al., 1978). Before subjects took part in a misinformation experiment, we gave them a plain tonic beverage and told them it was either a vodka and tonic or a plain tonic drink. Because alcohol placebos affect behaviors in the sphere of social influence but not outside it, we had two predictions: First, because the effect of misleading PEI is influenced by social factors, we predicted that subjects told they drank alcohol (told-alcohol subjects) would be more prone to misleading PEI than subjects told they drank plain tonic ( told-tonic subjects). Second, because memory for the slide sequence (in the absence of misleading PEI) would not be influenced by social factors, we predicted that subjects in the two groups would be equally accurate on control items. This second prediction fit with Yuille and Tollestrup’s (1990) finding that subjects given an alcohol placebo and those who drank no beverage at all reported a staged event equally accurately. However, there were also reasons to predict that alcohol placebos might cause other patterns of memory distortion. For example, toldalcohol subjects might have poorer event memories for event slides not because they were more suggestible, but because they simply did not pay much attention to the slides. By the time they read the PEI, they might believe they were starting to sober up, and read the misleading narrative carefully. In this case, told-alcohol subjects would be less likely than told-tonic subjects to report correct control details, but more likely than told-tonic subjects to report incorrect details about which they had been misled. Yet another outcome was also plausible: Told-alcohol subjects might not pay attention to either the event or the PEI, and therefore might perform at chance levels on the memory test. In short, we were interested in whether subjects who were falsely told they were consuming alcohol would be more susceptible to misleading PEI than their counterparts who were correctly told they were consuming plain tonic. Such a finding would have theoretical implications for how both the misinformation effect and the functions of memory should be conceptualized.