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Friday, January 12, 2024

Out, damned spot: Can the “Macbeth Effect” be replicated?

Earp, B. D., Everett, J. A. C., et al. (2014).
Basic and Applied Social Psychology, 36(1), 91–98.


Comments on an article by Zhong, and Liljenquist (see record 2004-22267-003). Zhong and Liljenquist (2006) reported evidence of a “Macbeth Effect” in social psychology: a threat to people's moral purity leads them to seek, literally, to cleanse themselves. In an attempt to build upon these findings, we conducted a series of direct replications of Study 2 from Z&L's seminal report. We used Z&L's original materials and methods, investigated samples that were more representative of the general population, investigated samples from different countries and cultures, and substantially increased the power of our statistical tests. Despite multiple good-faith efforts, however, we were unable to detect a “Macbeth Effect” in any of our experiments. We discuss these findings in the context of recent concerns about replicability in the field of experimental social psychology.

Here is my summary:

In a seminal study published in 2006, Zhong and Liljenquist introduced the concept of the "Macbeth Effect," which suggests that moral transgressions lead to a desire for physical cleansing. This phenomenon was inspired by Shakespeare's play "Macbeth," in which Lady Macbeth's obsession with washing her hands reflects her guilt over her murderous actions.

Building on Zhong and Liljenquist's work, Earp et al. (2014) conducted a series of experiments to replicate the Macbeth Effect. They used various methods, including manipulating participants' moral states through writing tasks and exposing them to reminders of moral cleanliness. However, despite their efforts, they were unable to consistently find evidence for the Macbeth Effect.

The authors' inability to replicate the original findings raises questions about the robustness of the Macbeth Effect. They suggest that more research is needed to understand the conditions under which moral transgressions lead to a desire for physical cleansing. Additionally, they emphasize the importance of conducting replications in psychological research to ensure the reliability of findings.