Never in human history have our hands, and probably houses as well, have been so clean (well, I presume). I’m willing to bet you pretty much anything that we are washing our hands and faces much more often than before; and sales of soaps and cleaners, at least online, are soaring. The scent of spring this year is the scent of hand sanitizer. What we expect of this incessant cleaning is, clearly, that it keeps us healthy. What I didn’t expect before I researched the topic is that it also has important psychological effects. Here are three brilliant examples of how hand washing impacts our minds.

Reducing the need to justify past decisions

Cognitive dissonance is the term psychologists use to talk about the nagging feeling of indecisiveness you get when you need to choose between two items. Having difficulty deciding whether to go to Thailand or Brazil on your next vacation because both offer interesting possibilities? Don’t know which Netflix movie to watch next? Wanting to stay in bed but having work to do? Cognitive dissonance at its best.

How do we manage these situations? Very often by justifying our choice after we’ve made it and increasing our preference for what we’ve done. Sounds quite odd, but there is a lot of evidence that we actively try to convince ourselves that we’ve made the right choice, which makes us like our selected alternative even more.

You know what’s even more odd: the fact that this effect is gone if you wash your hands. To put it a different way, if you wash your hands after a difficult choice you won’t need to justify it to yourself. As the authors of the study put it, “[Washing] can … cleanse us from traces of past decisions, reducing the need to justify them.” Washing restores the clean pre-choice slate, freeing us from the need to defend our own choices to ourselves.

The “Macbeth effect”

A growing and insightful body of literature suggests that our cognition – how we see and subsequently act in the world – is shaped by, and in fact probably determined, by various aspects of our bodies beyond the brain itself. This is most clear with our abstract concepts, like moral, society, work, career, organization, etc. Because we lack direct perceptual evidence for them, what we do is transfer meaning from objects and experiences we know well. What do we know best? Yep, our bodies. This, in essence, is the theory of conceptual metaphor – that we equate concepts related to the physical worlds to ones in the non-physical one. This is why we can, for example, think of organizations as organisms and theories as buildings. This is also why we associate morality with cleanliness and can easily say that we have pure thoughts, although thoughts lack any physical presence.

The ‘Macbeth effect’ is a function of this body-mind relationship. After Lady Macbeth commits murder she constantly and to no avail tries to clean her hands of the bloodstains she imagines there. Similarly, in a number of studies “This effect revealed itself through an increased mental accessibility of cleansing related concepts, a greater desire for cleansing products, and a greater likelihood of taking antiseptic wipes.” * It also turns out that washing one’s hands reduces the amount of moral emotions (such as regret, guilt, shame, and embarrassment) they feel, but it doesn’t impact non-moral emotions.

An effect of these findings with fewer benefits for society is that washing our hands washes away our sins thus making us less likely to compensate for them. What does this mean? That we are less likely to volunteer to help: “…physical cleansing significantly reduced volunteerism: 74% of those in the not-cleansed condition offered help, whereas only 41% of participants who had a chance to cleanse their hands offered help.”

Before you dispair

The fact that we tend to volunteer less after we’ve washed away our sins with soap seems despairing – at the end of the day, in times like the Covid-19 crisis we want to inspire people to help each other. In what at first sight appears to contradict the Macbeth effect, another study found that clean-scents promotes virtuous behavior. Study participants in a clean-scented room showed higher trust, returning almost twice as much money to a randomly assigned counterpart in a typical trust game. In addition,

“… participants in the clean-scented environment expressed greater interest in volunteering than control participants. Additionally, a greater proportion of participants in the clean-scented rooms indicated a willingness to donate money.”

The Smell of Virtue: Clean Scents Promote Reciprocity and Charity

So while actually washing your hands refreshes us to a clean slate, decreases our need to compensate for our wrongdoings, and makes us less likely to help others, being primed with cleanliness makes us more likely to engage in prosocial behavior. Why the different effects? The short answer is that “…actual physical cleaning and priming of cleaning led to changes in different brain regions and networks…” You can find out more in this article.

I still wonder which of the two prevails in the current situation in which we are at the same time surrounded by clean scents and wash our hands constantly. That, it seems, is for the future to show. One thing is clear: physical cleanliness, reflected in simple mundane activities like washing our hands, impacts our minds much more than we recognize. Now we know.

My best wishes for a great day ahead!

* Note that other studies have not been able to replicate these findings:

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