After she assists her husband to commit murder, Lady Macbeth is racked with guilt and so begins to compulsively wash her hands in an effort to wash away the imaginary blood stains there. Now, a University of Cologne researcher has investigated how physical cleansing may affect us after failure. It's not murder but it still matters. The results? People who washed their hands after failing a task were more optimistic yet less successful in performing future tasks than those who did not cleanse away their disappointment. His findings were published recently in Social Psychological and Personality Science.

To examine potential psychological and performance effects of hand washing, Kaspar divided 98 experiment participants into three groups. For part one of the experiment, participants from two groups had to solve an impossible task, while participants in the third group did not participate in the task. Kaspar discovered that both groups who failed the task felt optimistic that they would do better the next time, whether they had washed their hands or not. However, he also discovered the group who had washed their hands were more optimistic than those who did not.

Next, he requested all participants attempt a second task. Oddly the results of his experiment defied his expectation: participants who did not wash their hands did considerably better than participants who had washed their hands. In fact, the performance of the cleaner participants was on a par with the third group, who had not experienced previous failure. Although physical cleansing may eliminate negative feelings after failure, Kaspar believes, it may also eliminate the motivation to try harder in order to refresh and renew the self-perception of competence.

Is The "Macbeth Effect" Universal?

Kaspar's work was launched by previous work in the area of self-cleansing. In particular, one 'classic' study from 2006 explored the relationship between bodily purity and moral purity — or, what they termed the “Macbeth effect.” In three experiments, Chen-Bo Zhong and Katie Liljenquist, a pair of Canadian and American researchers, showed how a threat to one's moral purity spurred the need to cleanse oneself.

"Daily hygiene routines such as washing hands, as simple and benign as they might seem, can deliver a powerful antidote to threatened morality, enabling people to truly wash away their sins,” the authors noted in their concluding remarks.

This effect seems like it might be a universal truth. Yet, when another set of American and Canadian researchers as well as a team from Universidad de La Laguna in Spain attempted to replicate the 'Macbeth effect’ study, they were surprised to find they could not do so. In fact, in the years since the original experiments were performed, no one has succeeded in replicating them yet.

Sources: Kaspar K. Washing One’s Hands After Failure Enhances Optimism but Hampers Future Performance. Social Psychological and Personality Science. 2013.

Zhong C-B, Liljenquist K. Washing Away Your Sins: Threatened Morality and Physical Cleansing. Science. 2006.

Gamez E, Diaz JM, Marrero H. The Uncertain Universality of the Macbeth Effect with a Spanish Sample. The Spanish Journal of Psychology. 2011.

Fayard JV, Bassi AK, Bernstein D M, Roberts B W. Is cleanliness next togodliness? Dispelling old wives’ tales: Failure to replicate Zhong and Liljenquist. Journal of Articles in Support of the Null Hypothesis. 2009.