The Effects of Placebos on Eyewitness Memory Distortions

Abstract

Can being under the influence of a supposed substance affect the degree to which people experience memory distortions? Four experiments were conducted to investigate how both memory impairing and memory enhancing placebos affected eyewitness memory performance. Experiment 1 investigated whether alcohol placebos would affect performance in an eyewitness memory test. Subjects drank a plain tonic water beverage, but half were told it was a vodka and tonic. Subjects then took part in a typical three-stage eyewitness memory experiment (Loftus, Miller & Burns, 1978). The results showed that "Told Alcohol" subjects were more swayed by misleading postevent information (PEI) compared to "Told Tonic" subjects. Experiment 2 evaluated whether subjects who were led to believe they had taken a cognitive boosting drug were protected from memory distortions. Subjects drank a concoction comprised of water and lime-flavoured baking soda. Using a procedure similar to Experiment 1, half were told their drink contained a cognitive enhancing drug called R273, and the other half were told that it contained an inactive version of the same drug. Subjects who had been led to believe that their drink contained R273 were protected from misleading PEI. Experiments 3a and 3b investigated whether the finding that placebos could improve memory were applicable to a real world setting. These two experiments examined whether ginkgo biloba, an existing popular herbal supplement believed by many to have memory enhancing properties, would work to protect people from experiencing memory distortions? The results from these two studies showed that the suggestion that one had taken ginkgo was not enough to positively influence memory performance, but was enough to influence how subjects perceived their cognitive abilities. Taken together, these results have theoretical implications for how memory is conceptualised. Furthermore, these results suggest that at least to some degree, we have control over our susceptibility to memory distortions.