Open Access Te Herenga Waka-Victoria University of Wellington
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Placebos Affect Retrospective and Prospective Memory Performance by Increasing Monitoring

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posted on 2021-11-09, 19:39 authored by Parker, Sophie Louise

Decreasing physical pain, increasing emotional wellbeing, and improving physical health are just some of the ways placebos have affected people's physiological and psychological health (Crum & Langer, 2007; Kirsch & Sapirstein, 1999; Montgomery & Kirsch, 1997). Recently, Clifasefi, Garry, Harper, Sharman, and Sutherland (2007) demonstrated that a memory placebo called R273 could even reduce people's susceptibility to misleading information. Yet how could a substance with no physiologically active properties affect memory performance? That is the overarching question of this thesis. In order to monitor the sources of information about the past, and in order to remember future tasks and actions, people can either use an effortful monitoring process, or they can rely on their usual, automatic and effortless memory processes. Typically, the more monitoring that people use, the better their memory performance (Johnson, Hashtroudi, & Lindsay, 1993; Einstein et al., 2005). In this thesis, over three experiments, I examined how a placebo might affect the way people monitor information, thus improving aspects of retrospective and prospective memory. Experiment 1 examined whether R273 reduces people's susceptibility to the misinformation effect by leading them to switch from their habitual, automatic, and easy source monitoring to more deliberate and effortful source monitoring. To examine this question I used Clifasefi et al.'s (2007) sham drug procedure and then ran subjects through a three-stage misinformation experiment (Loftus, Miller, & Burns, 1978). The results of Experiments 1 suggest that R273 did not affect effortful monitoring during the post event information (PEI), but did affect effortful monitoring during the memory test. Experiment 2 aimed to find further evidence that R273 affects people's monitoring during the memory test. To address this question, all subjects were told that they had received an inactive drug before they took part in the first two stages of the misinformation effect paradigm. Immediately before taking the memory test, however, I falsely told some people that they had actually received R273. The primary finding of Experiment 2 added support to the idea that R273 affects subjects source monitoring during the memory test: Told Drug subjects were less misled than their Told Inactive counterparts. Finally, Experiment 3 further examined whether R273 leads people to use effortful monitoring, but did so using a prospective memory task, whose underlying memory processes align closely with those of source monitoring. The results showed that Told Drug subjects were slower to perform an ongoing and concurrent task, yet had better prospective memory performance than Told Inactive subjects. These results suggested that R273 lead Told Drug subjects' to use more effortful monitoring. In conclusion, the results suggest that the sham cognitive enhancing placebo R273 improves people's ability to resist misleading suggestion, and perform prospective memory tasks because it leads them to use more effortful monitoring.


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Date of Award



Te Herenga Waka—Victoria University of Wellington

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Author Retains Copyright

Degree Discipline


Degree Grantor

Te Herenga Waka—Victoria University of Wellington

Degree Level


Degree Name

Doctor of Philosophy

Victoria University of Wellington Item Type

Awarded Doctoral Thesis



Victoria University of Wellington School

School of Psychology


Garry, Maryanne; Harper, David