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Citation: Lee, S. W. S., & Schwarz N. (in press). Clean-moral effects and clean-slate effects:

Physical cleansing as an embodied procedure of psychological separation. In R. Duschinksy, S.

Schnall, & D. Weiss (Eds.), Purity and danger now: New perspectives. London: Routledge.

Clean-Moral Effects and Clean-Slate Effects:

Physical Cleansing as an Embodied Procedure of Psychological Separation

Spike W. S. Lee Norbert Schwarz

University of Toronto University of Southern California

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Handwashing is one of the easiest and most effective opportunities to enjoy substantial

health benefits. Meta-analytic evidence associates handwashing with reduction in risks of

diarrhea diseases by 42-47%, severe intestinal infections by 48%, and shigellosis by 59%;

extrapolation analyses suggest that handwashing could avert 0.5-1.4 million potential diarrhea

deaths (Curtis & Cairncross, 2014). In a randomized controlled trial of 906 households in

Karachi, Pakistan, households that were (vs. were not) given handwashing promotion and plain

soap showed substantial reductions in childhood incidences of pneumonia (by 50%) and acute

lower-respiratory infections (e.g., diarrhea by 53%). Antibacterial soap worked similarly well

(Luby et al., 2005) on these two clinical syndromes that bring about the most childhood deaths

around the world, especially in poor communities in developing countries. Similar effects of

handwashing promotion on respiratory-tract infections and respiratory illness have been found

among children and adults in developed countries including Canada, Australia, and the U.S.

(Carabin et al., 1999; Master, Hess Longe, & Dickson, 1997; Niffenegger, 1997; Roberts et al.,

2000; Ryan, Christian, & Wohlrabe, 2001). The health impact of handwashing is significant

enough that October 15 is designated as the annual Global Handwashing Day, when people all

over the world are educated about the practices and benefits of effective handwashing.

Thanks to the cheap mass production and global reach of soaps and detergents since the

20th century, their physical properties have been meticulously documented (American Cleaning

Institute, 2015). Cleanliness has become a fabric of modern life, a part of our daily routine, an

easy mechanism for the avoidance of contamination, pollution, and diseases to enhance our

chances of survival (Feder, 2015). But cleanliness comes with more than just physical properties

and biological benefits—it has rich symbolic meanings, in both primitive and modern cultures,

religious communities and secular societies, an insight given by Mary Douglas (1966) in her

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classic collection of anthropological observations half a century ago. Experimental research in

the last decade has vastly expanded upon this theme to generate causal evidence that cleanliness

provides mental and behavioral benefits across many domains of contemporary life. These

psychological aspects and consequences of cleanliness are the focus of our chapter.

At first glance, the association of cleanliness with abstract symbolic meanings seems like

a matter of faith. The proverb goes, “Cleanliness is next to godliness.” Across the world’s major

religions, ritual purification symbolizes spiritual purification, as in Christians’ baptism, Judaists’

mikvah, Muslims’ and Buddhists’ ablution, Hindus’ bathing in the Ganges River, and Sikhs’

amrit. The religious overtones are so obvious that even non-religious people unconsciously

associate purity with religiosity (Preston & Ritter, 2012).

Yet cleanliness is not limited to religious contexts. As we review the burgeoning body of

psychological research on cleanliness in this chapter, we will first see that cleanliness is linked to

numerous moral experiences, which have received the lion’s share of empirical and theoretical

attention. But the story turns out to be much broader than that. Cleanliness exerts psychological

effects far beyond the realm of morality: A sense of cleanliness appears to wipe the mental slate

clean. It reduces the residual influence of threats to different facets of the self as well as the

residual influence of various positive experiences. Merely cleaning one’s hands with an

antiseptic wipe, for example, is enough to reduce one’s guilt (Zhong & Liljenquist, 2006), doubts

(Lee & Schwarz, 2010a), and the impact of previous streaks of good or bad luck (A. Xu, Zwick,

& Schwarz, 2012). Clean-slate effects appear valence- and domain-general, leading us to

conceptualize physical cleansing as an embodied procedure of psychological separation. This

procedural perspective integrates existing findings, reveals possible deeper mechanisms, and

makes novel predictions about the boundary conditions of clean-slate effects.

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Clean and Moral

Most psychological research on cleanliness has focused on its metaphorical associations with

morality, consistent with the dominant theme of Douglas’s (1966) seminal work. In current

theorizing, the link between cleanliness and morality is often traced to a conceptual metaphor

that embodies abstract thoughts about morality in concrete experiences of cleanliness (Lakoff &

Johnson, 1980; Landau, Meier, & Keefer, 2010; Lee & Schwarz, 2011, 2014). Numerous

expressions – from “clean hands and a pure heart” to “dirty thoughts and filthy behaviors” –

illustrate the close connection in all languages studied. It is assumed to result from the

scaffolding of higher mental processes upon lower sensorimotor processes over developmental

time (Lakoff & Johnson, 1999; Williams, Huang, & Bargh, 2009). It is also compatible with the

principle of neural reuse, which assumes that existing neural mechanisms acquire new functions

over evolutionary time (Anderson, 2010).

Some findings support the assumption that moral experiences implicate an embodied

metaphorical link to cleanliness. For example, when people were induced to convey a lie on

voicemail (using their mouth), they were subsequently attracted to mouthwash, but not hand

sanitizer; conversely, when induced to convey the lie on email (using their hands), they were

attracted to hand sanitizer, but not mouthwash (Lee & Schwarz, 2010b). Moreover, their

evaluation of mouth-cleaning vs. hand-washing products was associated with higher activities in

the respective sensorimotor neural regions (Denke, Rotte, Heinze, & Schaefer, 2014; Schaefer,

Rotte, Heinze, & Denke, 2015). The assumption that the conceptual metaphor is grounded in

sensorimotor modalities further predicts that moral experiences should influence basic

sensorimotor experiences of cleanliness and vice versa (cf. Lee & Schwarz, 2012). Observing

that clean and dirty are often represented in white and black colors, G. Sherman and Clore (2009,

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Study 1) demonstrated that people judged the color of a word more quickly when moral words

were shown in white and immoral words in black than vice versa. The more strongly people

showed the effect on this moral Stroop task, the more desirable they judged shower soap and

toothpaste to be (Study 3). Furthermore, embodied conceptual metaphors are conducive to

multimodal priming (Lee, in press), so moral effects should be evoked by cleanliness experience

in its various modalities. Numerous studies, as we will now review, show that tactile, olfactory,

and visual experiences of cleanliness are capable of changing both moral self-evaluation and

moral judgments and behaviors towards others.

Cleanliness and the Moral Self

Feeling immoral elicits the pursuit of cleanliness. For example, after describing their past

unethical (vs. ethical) behavior, people completed more cleansing-related word fragments and

became more likely to choose an antiseptic wipe over a pencil as a free gift (Zhong &

Liljenquist, 2006, Studies 1 & 3). Subtle procedures such as hand-copying a story, written in the

first-person perspective, of an unethical (vs. ethical) lawyer also increased people’s desires for

cleaning but not non-cleaning products (Study 2). But blatant procedures backfire. For example,

when people were first asked to complete 183 items about their conscientiousness, which

invoked concepts such as how orderly and organized they are, then describing their past

unethical (vs. ethical) behavior did not increase their likelihood of choosing an antiseptic wipe

over a pencil as a free gift (Fayard, Bassi, Bernstein, & Roberts, 2009, Study 1). A possible

reason was that completing many items about being orderly and organized made these meanings

salient and made it more likely that people saw a link between being orderly and being ethical.

As observed in many social cognition studies, awareness of a potential influence elicits mental

corrections that counteract the otherwise observed effect (e.g., Strack, Schwarz, Bless, Kübler, &

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Wänke; 1993; for a review, see Schwarz, 2015).

Physical cleansing confers a sense of morality and boosts moral self-evaluation. For

example, after describing their past unethical behavior, people who had (vs. did not have) an

opportunity to use an antiseptic wipe reported lower feelings of disgust, regret, guilt, shame,

embarrassment, and anger, and became less likely to volunteer their time for an unpaid

experiment, presumably because they felt morally cleansed and were less driven to engage in

compensatory prosocial behavior (Zhong & Liljenquist, Study 4). Quasi-experimental work also

shows that people cheated more after (vs. before) taking a shower (Lobel et al., 2015, Study 1)

and donated less money to charity after (vs. before) bathing for religious purification (Study 2).

Because active moral concerns can interfere with other cognitive tasks, we may further

expect cleansing to reduce these interference effects. Indeed, after describing a past unethical

behavior, people who had (vs. did not have) an antiseptic wipe to use showed weaker

interference effects in a Stroop task (but not more facilitation effects), weaker interference

effects in an object interference task, and faster stop-signal reaction time in a stop-signal task

(Kalanthroff, Aslan, & Dar, 2015). Apparently, cleansing increases cognitive flexibility,

presumably by freeing people’s minds from ruminating about moral failures.

Vicarious Experience of Morality and Cleanliness

Vicarious experience of a behavior is weaker in intensity than direct enactment of the

behavior (Barsalou, 2008). Hence, vicarious manipulations of morality, like copying a story

about someone else’s immoral behavior, are likely to come with less reliable cleanliness effects

than recalling one’s own immoral behavior (e.g., Earp, Everett, Madva, & Hamlin, 2014).

Similarly, vicarious manipulations of cleansing are likely to exert weaker moral effects.

For example, after describing an incident of doing something bad to someone, people

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who experienced vicarious cleansing by watching a 2-min video of someone else typing numbers

on a keyboard and wiping the fingers, palm, and back of both hands (vs. of someone else typing

numbers on a keyboard only) were less likely to complete and return some questionnaires 3

weeks later, but the effects were weaker than if people actually typed the numbers themselves

and wiped their own fingers, palm, and back of both hands (H. Xu, Bègue, & Bushman, 2014).

The observed linear effect of self vs. other vs. no wiping on the number of questionnaires

completed and returned was mediated by participants’ state guilt, suggesting that direct cleansing

had stronger effects than vicarious cleansing on both immediate guilty feelings and subsequent

guilt-driven behavior weeks later.

Cleanliness and the Moral Self in Social Comparison

Moral self-evaluation is subject to social comparison (Festinger, 1954). For example, in

an experiment allegedly about food preferences (Cramwinckel, van Dijk, Scheepers, & van den

Bos, 2013, Study 1), people tasted a meat sausage and then encountered another “participant”

(actually a confederate) who refused to taste the sausage for moral (vs. non-moral) reasons.

People disliked the moral refuser more and showed physiological changes that indicated a

motivational state of threat, presumably because social comparison with the moral refuser

threatened one’s own moral standing. But if people had an opportunity to clean their hands, they

liked the moral refuser more, considered the moral refuser less agentic, and evaluated themselves

more positively, especially if they had a strong moral identity (Study 2).

When people think about their own moral failures, they become particularly sensitive to

others’ moral failures, which provide an opportunity for self-serving social comparisons (“Look,

others are worse than me, so I’m not too bad”). Accordingly, people condemn others who have

moral failures as dirtier and more evil and, by contrast, see themselves as cleaner and more

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moral. For example, people who read about a target person being guilty of theft and punished

(vs. guilty but not punished, or vs. not guilty) reported feeling physically cleaner themselves, but

only if they had been asked to recall their own unethical experience beforehand, not if they had

been asked to recall a very boring experience (Rothschild, Landau, Keefer, & Sullivan, 2015,

Study 1). Recalling their own unethical (vs. a very boring) experience also increased people’s

tendency to judge a hit-and-run driver (described in an article with his photo shown) as evil

(Study 3) and as physically dirty, mediated by higher levels of their own current feelings of guilt

(Study 2).

A Clean, Moral Self in Different Areas of Life

Cleanliness is linked to moral concerns in many important areas of life, such as law and

violence, business, and sex.

In court proceedings, evidence that is obtained through illegal means is often considered

legally “dirty”. Indeed, lawyers and law students who were induced (vs. not induced) to use

inadmissible evidence (produced from a police officer’s racially motivated search) were more

likely to choose a small bottle of Purell hand disinfectant over a highlighter pen as a free gift

(Bilz, 2012, Study 3), paralleling findings in other domains of moral transgression. Similarly,

people who read criminal (vs. neutral) vignettes completed more cleansing- and disgust-related

word fragments and were more likely to choose an antiseptic wipe or soap over a pen holder as a

free gift (Jones & Fitness, 2008, Study 1). After playing a video game involving violence against

humans (vs. objects), people were more likely to choose cleaning products, an effect that was

mediated by greater moral distress and that emerged only among inexperienced players, not

among experienced ones (Gollwitzer & Melzer, 2012). This suggests that repeated exposure to

violence may mute people’s moral distress and associated desires for cleanliness.

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In the business world, networking is valued, but when motivated by dubious goals, it can

feel dirty and elicit the pursuit of cleanliness (Casciaro, Gino, & Kouchaki, 2014). For example,

recalling an experience of instrumental (vs. spontaneous) networking increased people’s

tendency to complete cleansing-related word fragments; this effect was stronger for recall of

professional (vs. personal) networking (Study 1). Even reading a story and imagining being the

main character who engaged in professional instrumental (vs. personal spontaneous) networking

could increase people’s desires for cleaning over non-cleaning products, mediated by their

stronger feelings of dirtiness, inauthenticity, and discomfort; it also increased their negative but

not positive affect (Study 2). Actually sending a message for professional networking via

LinkedIn (vs. personal networking via Facebook) increased people’s desires for cleaning but not

non-cleaning products, although only among people who were assigned a low-power (vs. high-

power) role (Study 4).

Power may moderate cleanliness effects because being in a low-power role may elicit

conformist intentions and inauthentic behaviors, which leave people with a sense of impurity.

For example, people who recalled experiences of being inauthentic (vs. authentic) to themselves

reported lower moral self-regard and stronger feelings of impurity (Gino, Kouchaki, & Galinsky,

2015, Study 1), completed more cleansing-related word fragments, and judged cleaning products

and behaviors but not non-cleaning products and behaviors as more desirable (Study 2),

regardless of whether their recalled inauthentic (vs. authentic) experience involved lying (vs.

telling the truth) to others or not. People who described an experience of being inauthentic to

themselves (vs. failing an activity, or vs. their activities from the previous day) were also more

likely to volunteer time to the experimenter, mediated by stronger feelings of impurity (Study 3).

These effects appear to be driven by a link between inauthenticity and impurity rather than by

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cognitive dissonance, as writing a counterattitudinal (vs. proattitudinal) essay increased people’s

desires for cleaning but not non-cleaning products, regardless of whether they wrote the

counterattitudinal essay with a high or low sense of choice (Study 4). If the effect were driven by

cognitive dissonance, the sense of choice should have mattered; it did not. Finally, using a

cleansing product (hand sanitizer; vs. examining a pen) decreased people’s likelihood and

amount of donation if they had recalled an experience of being inauthentic to themselves, but not

if they had recalled an experience of being authentic to themselves (Study 5).

Sexual behavior is of particular interest to the clean-moral link because sex is more

inherently physical than other moral concerns, such as fairness, and it has been at the center of an

ongoing debate about the theoretical structure of morality (cf. Giner-Sorolla & Sabo, this

volume; see also the debate among Frimer, Gray, Haidt, and Pizarro at SPSP 2016). Empirically,

men who listened to an audio recording to vividly imagine non-consensually (vs. consensually)

kissing a young woman at a party later showed higher levels of self-reported dirtiness (Rachman,

Radomsky, Elliott, & Zysk 2012, Studies 1-4), actual washing behaviors (Studies 2 & 3), urges

to wash (Studies 3 & 4), as well as increases in anxiety, shame, anger, guilt, and sadness (Study

4).

Conversely, being the victim of sexual innuendo triggers dirty feelings. Women who

received objectifying (vs. non-objectifying) positive comments from a male confederate reported

greater sinful feelings and stronger desires for cleaning but not non-cleaning products, both

effects being mediated by increased feelings of dirtiness (Chen, Teng, & Zhang, 2013, Study 1).

Women who recalled a social interaction with a man who objectified them (vs. responded

appropriately) reported greater sinful feelings, mediated by an increased sense of contamination

(Study 2), but this effect occurred only among women high on perceived personal responsibility

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for being objectified, not among women low on it (Study 3).

Summary

Seeing oneself as immoral prompts one’s pursuit of cleanliness, which by metaphorical

association boosts one’s moral self-evaluation. Both morality and cleanliness can be manipulated

vicariously (as opposed to directly) to produce similar but weaker effects. One way to

manipulate how moral people feel about themselves and others is by social comparison. Mutual

influences between the moral self and physical cleanliness are observed in many important areas

of life, such as law and violence, business networking, and sexual morality.

Cleanliness and Moral Judgment and Behavior Towards Others

One’s sense of cleanliness also shapes moral judgments and behaviors towards others.

There are two broad ways to manipulate “the sense of cleanliness.” One is to manipulate actual

cleansing (e.g., washing hands with soap, wiping hands with an antiseptic wipe), which is what

researchers did in all of the studies reviewed above that examined cleanliness as an independent

variable. Another way is to manipulate clean cues (e.g., clean scents, clean room). Both kinds of

manipulation work by conferring a sense of cleanliness, but their exact effects depend on what

the sense of cleanliness bears on and what precedes it (Lee & Schwarz, 2011). Such context-

sensitivity is consistent with the malleable nature of inferences from other phenomenal

experience (Schwarz, 2012) and affords a variety of judgmental and behavioral effects. If people

are induced to feel immoral about their past transgressions, then a sense of cleanliness reduces

their morally dirty feelings and they are less motivated to engage in compensatory prosocial

behaviors and they feel more licensed to engage in self-interested behaviors (see the “Cleanliness

and the Moral Self” section above). If people are induced to feel disgusted about the acts of

someone else, then a sense of cleanliness reduces residual disgust and thus reduces its

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intensification effect on people’s judgment towards others’ immoral behaviors. If no particular

event precedes a manipulation of clean cues or actual cleansing, the sense of cleanliness may

bear either on the self or on others. If it bears on others, it renders others’ immoral behaviors less

dirty and less bad. If it bears on the self, one sees the self as cleaner and more moral and others

as dirtier by comparison.

Cleanliness Can Reduce Disgust and Its Effect on Moral Judgment

Moral judgment is harsher when people experience disgust, even if the disgust was

incidentally induced by watching an unrelated video clip (e.g., Schnall, Haidt, Clore, & Jordan,

2008). This impact of disgust is attenuated when people washed their hands prior to judgment

(Schnall, Benton, & Harvey, 2008, Study 2). Similarly, using (vs. examining) an antiseptic wipe

weakened the association between self-reported germ aversion and unfavorable attitudes towards

outgroups (J. Y. Huang, Sedlovskaya, Ackerman, & Bargh, 2011, Study 3).

Cleanliness Bearing on Others Can Soften Moral Judgment of Them

People who unscrambled sentences containing cleanliness-related (vs. neutral) words

judged moral transgressions as a little less wrong, despite no change in their negative or positive

emotions (Schnall, Benton, & Harvey, 2008, Study 1). For this kind of manipulation to be

effective though, it has to elicit relatively low processing effort (J. L. Huang, 2014), or else it

may not work (Johnson, Cheung, & Donnellan, 2014), consistent with the finding that once

primed cues are overly salient, they lose their influence on judgments (Strack et al., 1993;

Schwarz, 2015).

Extending beyond the conceptual activation of a sense of cleanliness through words,

actual cleansing can reduce physiological changes as well as moral judgment. In a recent

experiment (Kaspar, Krapp, & König, 2015), people saw a number of moral and immoral images

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and judged how moral or immoral each was, while their eye movements were being tracked.

Halfway through the task, there was a break. If people were prompted to wash their hands (vs.

simply waited), afterwards they judged immoral images as less immoral and moral images as

less moral, and showed corresponding changes in pupil size.

Cleanliness Bearing on the Self Can Promote Moral Behavior Towards Others

Incidental cleanliness cues can elicit moral behavior. For example, when people played a

trust game in the recipient role, they were more cooperative and returned more money to the

sender if they were in a room sprayed (vs. not sprayed) with citrus-scented Windex (Liljenquist,

Zhong, & Galinsky, 2010, Study 1). The same manipulation also increased intention to volunteer

for Habitat for Humanity and fund donation, despite little change in positive or negative affect

(Study 2).

The flip side of the beneficial effect of cleanliness cues is that dirtiness cues can reduce

moral behavior. For example, vendors at a local farmers’ market who received a dirty (vs. clean)

banknote from a “customer” (who was in fact a confederate) gave a smaller amount of

vegetables to the customer on a second purchase (Yang, Zhou, Mead, Vohs, & Baumeister, 2013,

Study 1). After people counted dirty (vs. clean) bills, they returned less money in a one-shot trust

game (Study 2) and demanded less money for performing unfair or harmful behaviors (but not

for performing behaviors that would violate ingroup/loyalty, authority/respect, or purity/sanctity;

Study 3). They also reciprocated less in rounds of prisoner’s dilemma games where they

expected the partner to be a cooperator (but not in rounds where they expected the partner to be a

defector; Study 4), and were less likely to reject small unfair offers in ultimatum games (but not

unfair large offers or fair offers; Study 5).

These behavioral effects of cleanliness and dirtiness cues are mediated by changes in

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moral attitudes. Counting ordinary bills after reading a news article about how dirty the country’s

paper currency was (vs. a recent weather report) decreased people’s offers in rounds of dictator

games with allegedly different receivers, mediated by less positive ratings of exchange-related

words (Study 6) or by increased agreement with greed-related sayings (Study 7). Conversely,

counting ordinary bills after reading a news article about how clean the country’s paper currency

was (vs. a recent weather report) increased people’s positive ratings of exchange-related words

(Study 6) and increased their offers in rounds of dictator games with allegedly different

receivers, mediated by decreased agreement with greed-related sayings and increased agreement

with fairness-related ones (Study 7).

Cleanliness Bearing on the Self Can Intensify Moral Judgment of Others

People who were (vs. were not) asked to clean their hands with an antiseptic wipe judged

various social issues as more immoral (Zhong, Strejcek, & Sivanathan, 2010, Study 1). Merely

imagining cleansing can have similar effects. People who read a passage written in the first-

person perspective that prompted detailed visualization of being clean (vs. dirty, or vs. not

reading anything) judged social issues as more immoral (Study 2), mediated by higher ranking of

themselves over fellow students on moral character (but not on other dimensions; Study 3).

Compared with my own clean and moral self, the social issues out there feel dirty and immoral.

In addition to actual or imagined cleansing, subtle cues of cleanliness also change moral

judgments and political attitudes. For example, simply being asked to “step over to the hand-

sanitizer dispenser (vs. the wall) to complete the questionnaire” increased people’s self-reported

conservative political attitudes in moral, social, and fiscal domains (Helzer & Pizarro, 2011,

Study 1). This observation is consistent with the more general finding that conservatives put

more value on purity and are more disgust-sensitive (Graham, Haidt, & Nosek, 2009; Haidt,

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2012; Inbar, Pizarro, & Bloom, 2009). Similarly, people who completed a computer

questionnaire next to a sign about cleanliness and after using an antiseptic wipe (vs. without the

sign and without receiving any wipe) judged sexual purity violations to be more wrong, mediated

by more conservative political attitudes (Study 2).

Summary

A sense of cleanliness, elicited by either subtle cues or actual cleansing, changes moral

judgments and behaviors towards others. Depending on what it means and what it bears on, it

can weaken compensatory prosociality and promote self-interested behaviors; or it can reduce

disgust and soften moral judgments towards others; or it can render the self clean and moral,

elicit identity-consistent moral behaviors, and make others’ immoral behaviors seem even more

dirty and immoral. A full understanding of the moderating variables remains wanting.

Modality-Specific Grounding of Morality in Cleanliness

All of the findings reviewed so far are consistent with two possible accounts. (1)

Cleanliness is linguistically and semantically associated with morality. (2) Cleanliness is the

embodied grounding of morality. Unlike the linguistic-semantic view, the embodied view

assumes that mental representations of morality are grounded in sensorimotor modalities

implicated in cleanliness. As such, it uniquely predicts modality-specific links between morality

and cleanliness. These links emerge when a modality is temporarily or chronically salient.

Temporarily Salient Modality

Cleanliness effects are strongest on the specific modality made temporarily salient by a

transgression. For example, people who had typed a lie on email (manual modality) evaluated

hand sanitizer more favorably than mouthwash, whereas people who had told a lie on voicemail

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(oral modality) evaluated mouthwash more favorably than hand sanitizer (Lee & Schwarz,

2010b; see Schaefer et al., 2015 for a replication). People who listened to a recording or rewrote

a story that prompted them to vividly imagine having to borrow and use a cell phone from a gay

(vs. heterosexual) man—which made the manual and oral modalities salient—completed more

cleansing-related word fragments (Golec et al., 2014, Study 1), indicating that the task brought

cleanliness concerns to mind. Acting on these concerns, they were more likely to choose a

disinfecting wipe over a pencil as a free gift (Study 2) and evaluated disinfectant hand wash and

mouthwash as more desirable, but not other body-cleaning, household-cleaning or non-cleaning

products as more desirable (Study 3).

Neural evidence further supports the role of temporarily salient modality in cleanliness

effects. For example, favorable evaluation of mouth-cleaning products after lying was associated

with neural activities in sensorimotor regions (Denke et al., 2014). Favorable evaluation of

mouthwash products after lying in a voice mail and favorable evaluation of hand-wash products

after lying in a written note were associated with the somatotopically organized neural activities

(Schaefer et al., 2015).

Chronically Salient Modality

In the above studies, cleanliness effects were strongest on the modality involved in the

transgression. Consistent with these temporary situational influences, cleanliness effects are also

stronger on the specific modality that is chronically salient in a culture. For example, East Asians

emphasize the face as a representation of their public self-image in sociomoral discourse.

Accordingly, face-cleaning was more effective in reducing guilt and regret when Chinese-

Canadian biculturals were primed with their Chinese background than when primed with their

Canadian background (Lee, Tang, Wan, Mai, & Liu, 2015, Study 1). When Chinese people used

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an antiseptic wipe to clean their face, it freed them from guilt-driven compensatory prosocial

behavior (Study 2), whereas cleaning their hands, or merely examining the wipe, did not. The

effectiveness of facial cleansing as a coping mechanism is further supported by Chinese people’s

specific interest in face-cleaning products and their tendency to engage in face-cleaning (vs.

hands-cleaning) behavior in the wake of their own immorality (Study 3).

Summary

These lines of evidence indicate that the clean-moral association shows the strongest

effects on whichever modality is salient, whether momentarily or chronically. The principle of

modality salience is not predicted a priori by the amodal view that morality is merely

linguistically or semantically associated with cleanliness. It is predicted a priori by the embodied

view that morality is grounded in sensorimotor modalities responsible for cleanliness experience

(see Lee & Schwarz, 2010b, for a discussion).

Individual Differences in Cleanliness and Morality

The embodied grounding of morality in cleanliness predicts that people should make

stronger moral judgment if they are sensitive to disgust (often evoked by dirtiness), to

cleanliness, or to their bodily experience in general. They should also show stronger clean-moral

effects if they have strong faith in their intuitions.

Disgust Sensitivity and Moral Judgment

Mock jurors high on disgust sensitivity exhibited a bias toward convicting criminals

(Jones & Fitness, 2008, Study 2). Disgust-sensitive people also considered it more likely that

suspects in crime vignettes were culpable, attributed more evilness to criminals, recommended

longer sentences for criminals, and perceived higher community crime levels (Study 3). People

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who frequently feel disgusted in daily life showed stronger disapproval of behaviors that violate

the moral foundation of purity and stronger approval of behaviors that uphold purity (whereas

trait anger and trait fear did not have the same predictive effects; Horberg, Oveis, Keltner, &

Cohen, 2009, Study 3).

Regarding the moral foundation of purity, disgust-sensitive people were more likely to

ascribe intentionality to an agent whose behavior had the side effect of causing gay men to kiss

in public (Inbar, Pizarro, Knobe, & Bloom, 2009, Study 1) and showed more unfavorable

automatic associations with gay people (vs. heterosexuals; Study 2). Stronger moral

condemnation of suicide was also predicted by higher disgust sensitivity, as were more intense

disgust responses to obituaries, stronger beliefs that suicide taints the victims’ souls, and greater

concerns about the moral foundation of purity (Rottman et al., 2014).

The predictive effects of disgust sensitivity, however, are not limited to the moral

foundation of purity or to moral violations that involve physical disgust (e.g., sexual immorality,

bloody murder). Higher disgust sensitivity also predicted stronger condemnation of moral

transgressions that go beyond the purity domain and involve no disgust and higher likelihoods of

moralizing violations of social conventions (Chapman & Anderson, 2014).

Sensitivity to Cleanliness or Bodily Experience and Moral Judgment

Excessive cleaning due to fear of contamination is the most common symptom of

obsessive-compulsive disorder (OCD; National Institute of Mental Health, 2016). Accordingly,

people with OCD show particularly strong cleanliness effects: After people described a past

unethical behavior, having (vs. not having) an antiseptic wipe to use decreased their feelings of

disgust, regret, guilt, shame, embarrassment, and anger, and their tendency to volunteer; these

effects were stronger among people with OCD than people without OCD (Reuven, Liberman &

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Dar, 2014).

Cleanliness is a bodily experience, and people higher on private body consciousness

(PBC) are more attentive to their internal bodily experiences (Miller, Murphy, & Buss, 1981).

Accordingly, people high on PBC show particularly strong cleanliness-related effects: People

who sat in a physically disgusting (vs. clean) room (Schnall, Haidt, et al., 2008, Study 2), wrote

about a physically disgusting experience (vs. skipped this task; Study 3), or watched a physically

disgusting (vs. sad, or vs. neutral) film clip (Study 4) judged moral transgressions as more

wrong, regardless of whether the transgressions themselves evoked disgust or not; these effects

were limited to people high on PBC and not observed among people low on PBC.

Faith in Intuition and Moral Judgment

In the eyes of moral rationalists (e.g., Kohlberg, 1969), moral judgment ought to be based

on abstract reasoning, not tethered to irrelevant bodily experiences like being dirty and disgusted

or feeling clean and pure. But as is obvious from the reviewed studies, people are susceptible to

influence from incidental feelings. Does it follow that clean-moral effects are stronger among

people who trust their gut feelings? On the one hand, there is evidence that after people imagined

writing a deceitful (vs. an apologetic) email, their willingness to pay for hand-cleaning products

(but not office supplies or general body care products) increased with their faith in intuition, even

controlling for their positive and negative affect (Ward & King, 2015, Study 1). On the other

hand, even professional philosophers, who supposedly rely less on intuition and gut feeling but

more on reflection and logical thinking, are susceptible to the influence of cleanliness:

Philosophers who completed surveys sprayed with clean scents (vs. odorless water) in a space

sprayed with clean scents (vs. odorless water) judged behaviors that violate the moral foundation

of purity to be less wrong from an observer’s perspective (Tobia, Chapman, & Stitch, 2013).

20

These findings raise more questions than they answer. They highlight the need to

investigate whether and how clean-moral effects interact with fast vs. slow mental processes

(Kahneman, 2011), what affective and cognitive mechanisms underlie them, and when and for

whom they are strongest.

Summary

Compatible with the embodied grounding of morality in cleanliness, moral judgments

and cleanliness effects are stronger for people sensitive to disgust, cleanliness, or bodily

experience. Investigating whether clean-moral effects are driven by feelings-as-information

(Schwarz, 2012) or also by other processes will allow clearer predictions about their personal

and situational moderators.

Specificity vs. Generality of the Link between Cleanliness and Morality

Are clean-moral effects specific to a particular kind of morality? One view holds that

different basic emotions are mapped onto different moral foundations. From this perspective,

disgust is the primary emotional response to violations of the moral foundation that has been

variously referred to as divinity, purity, or sanctity (Rozin, Lowery, Imada, & Haidt, 1999). But

the strength of the original evidence for this claim has undergone serious questioning (see

Chapman & Anderson, 2013, for details). In addition, multiple lines of counterevidence have

emerged, casting doubt on the specific mapping view. For example, facial expressions of disgust

can be evoked by violations of moral codes that are unrelated to divinity/purity/sanctity, like

fairness (Cannon, Schnall, & White, 2011; Chapman, Kim, Susskind, & Anderson, 2009).

Similarly, incidental manipulations of distaste (Eskine, Kacinik, & Prinz, 2011) and disgust

(Cheng, Ottati, & Price, 2013; Schnall, Haidt et al., 2008; Wheatley & Haidt, 2005) influence

moral judgments that are unrelated to divinity/purity/sanctity; and higher disgust sensitivity

21

predicts harsher condemnation of moral transgressions beyond the divinity/purity/sanctity

foundation (Chapman & Anderson, 2014). These findings suggest that moral disgust is more

general than initially thought.

The picture is further complicated by evidence for the pervasive role of anger in morality.

Anger is the predominant emotional response to moral transgressions that involve no physically

disgusting elements or, as some theorists argue, to moral transgressions in general, “irrespective

of the normative content involved” (Royzman, Atanasov, Landy, Parks, & Gepty, 2014, p. 892).

Consistent with this view, anger is evoked by violations of many sacred values, including

divinity/purity/sanctity violations (Tetlock et al., 2000). When people are asked to choose

between prototypically angry or disgusted behaviors in response to divinity/purity/sanctity

violations (e.g., disrespecting the Bible), they choose prototypically angry rather than disgusted

behaviors (Royzman et al., 2014). Indeed, anger results in harsher judgments of both

divinity/purity/sanctity and fairness violations (Cheng et al., 2013). Anger and disgust effects are

sometimes confounded or co-occurring. For example, both anger and disgust influence

judgments of harm (Ugazio, Lamm, & Singer, 2012); both anger and disgust can be evoked by

both harm and divinity/purity/sanctity violations (Cameron, Lindquist, & Gray, 2015). Table 1

provides an organized summary of the relevant findings (for full coverage of their details, see

Giner-Sorolla & Sabo, this volume).

Table 1. Emotional responses to disgusting and immoral stimuli.

Stimuli Response Distaste stimuli (e.g., bitterness) Disgust output Physically disgusting stimuli (e.g., feces) Disgust output Moral violations of divinity/purity/sanctity that involve or imply physically disgusting stimuli (e.g., incest)

Disgust output, but it may have nothing to do with the acts’ immoral nature (Rozin, Haidt, & McCauley, 2008)

22

Moral violations of divinity/purity/sanctity that do not involve or imply any physically disgusting stimuli (e.g., idolatry)

Disgust output can occur, but (1) whether it results from the same appraisals as to physically disgusting stimuli is unclear and (2) whether disgust is the predominant emotion is unclear because there is evidence for disgust (Chapman & Anderson, 2013) or anger (Royzman et al., 2014) as the predominant emotion

Moral violations of fairness that do not involve or imply any physically disgusting stimuli (e.g., biased resource allocation)

Disgust output can occur, but the same caveats as above apply

Moral violations of care, loyalty, and authority that do not involve or imply any physically disgusting stimuli (e.g., intentional harm, betrayal, disrespect)

Disgust output can occur, but anger seems to be the predominant emotional response

In short, there appears to be a multiplicity of relations between emotions and moral

foundations. Why is it so? One possible reason is that the supposedly singular foundation of

divinity/purity/sanctity, as is perhaps noticeable from its unwieldy plurality, is anything but

singular. Theorists have pointed out that measures of this foundation are fraught with confounds

and need to be, for lack of a better verb, “purified” such that they tease apart its multiple facets

and measure them more precisely (Pizarro, 2016; see also the debate among Frimer, Gray, Haidt,

and Pizarro at SPSP 2016). Pending such finer-grained measures, maybe we will see a specific

mapping between a particular emotion and a particular facet of divinity/purity/sanctity.

Another possible reason is that all moral foundations share a common, deeper cognitive

template that tracks an agent’s intentional harm on a patient (Gray, Young, & Waytz, 2012).

From this perspective, what appear to be different moral foundations are really different

manifestations of the same underlying process. This dovetails a constructionist view on the fluid,

context-sensitive links between emotion and morality (Cameron et al., 2015), hence the apparent

multiplicity in their relations.

The debate continues. But whether one sees disgust as specifically tied to one moral

23

foundation or as generally related to multiple moral foundations, both sides of the debate have

focused on the role of disgust, cleanliness, and purity within the realm of morality. Is cleanliness

only related to moral issues?

Beyond Morality: Defense Against Threats

An emerging stream of research shows that beyond its metaphorical associations with

morality, a sense of cleanliness reduces the residual influence of recent negative and positive

experiences, even if they have nothing to do with morality. We first review cleanliness effects on

threatening experiences, then on positive experiences, and finally propose an integrative

mechanism.

A Threat to the Rational Self

After people make a free choice between similarly attractive options, they often

experience postdecisional dissonance (“Did I make the right decision?”), which is a threat to

their rational self. It motivates people to justify their choice by developing a stronger preference

for the chosen over the rejected option (Brehm, 1956; Festinger, 1957). This classic “spreading

of alternatives” effect disappears once people wash or wipe their hands clean. After choosing

between two similarly attractive music albums, people tended to rank the chosen album as better

than the rejected album, but this tendency was eliminated once they had used (vs. examined) a

bottle of hand soap (Lee & Schwarz, 2010b, Study 1). Likewise, after choosing between two

fruit jams, people tended to expect the chosen jam to taste better than the rejected jam, but this

tendency was eliminated once they had used (vs. examined) an antiseptic wipe (Study 2).

An extended replication (Marotta & Bohner, 2013) showed that the ability to wipe off

cognitive dissonance was independent of people’s trait preference for consistency. It also showed

24

that using substances that lack a cleansing quality (a sticky chocolate rub) did not attenuate

dissonance. Finally, cleaning one’s hands was insufficient to reduce dissonance among people

high on brooding tendencies, intolerance of uncertainty, and generalized anxiety, but it reliably

eliminated dissonance among people low on these attributes (De Los Reyes et al., 2012).

A Threat to the Competent or Secure Self

Failures often lead people to feel less optimistic about their future performance and to put

in compensatory effort. Wiping off one’s failure is counterproductive under these conditions.

People who washed (vs. did not wash) their hands after failing a first anagram task showed more

optimistic expectations about their future performance on a second anagram task—but their

actual performance deteriorated, presumably through reduced effort (Kaspar, 2012).

Various cleansing effects—on the competent self, the rational self, and the moral self—

converge to suggest that a sense of cleanliness may be effective for reducing residual distress

from threats to any facet of the self (Millet, van der Wal, Grinstein, & Lee, 2016). Consistent

with this possibility, after watching a tension-inducing video clip of a physically threatening

scene, people who watched another video clip involving hand-washing (vs. circle-drawing, or vs.

egg-peeling) reported less tension (Study 1). Compatible effects emerged in the context of an

economic threat. People who watched a video about ongoing recession and described the process

of job search in times of high unemployment (vs. watched a video about oceanic nature and

described the process of doing laundry) evaluated cleaning but not non-cleaning products more

favorably (Study 2). The effect vanished once people affirmed values core to the self, consistent

with the hypothesis that a sense of cleanliness serves to protect the self from threats, unless it is

already protected (e.g., by self-affirmation).

Summary

25

A sense of cleanliness helps people cope with distress from threats to different facets of

the self. Following this reasoning, preliminary evidence shows that cleanliness effects are weaker

after self-affirmation. Whether cleanliness serves similar protective functions as self-affirmation

(D. Sherman & Cohen, 2006) in the face of all self-threats remains to be explored.

Beyond Morality: Clean-Slate Effects

All of the studies reviewed so far examined cleanliness effects on threatening

experiences, dovetailing Douglas’s (1966) interest in the symbolic meanings of cleanliness and

purity in contexts of danger and order maintenance. Yet there is evidence for cleanliness effects

on positive, non-threatening experiences as well. Cleansing appears to wipe the mental slate

clean. It exerts valence-general effects on diverse domains such as luck, endowment, and goals.

Luck

Not surprisingly, people are more willing to take risks when they think it is their lucky

rather than unlucky day. For example, Canadian business students who had to recall a good

financial decision took more risk on a subsequent financial decision task than people who had to

recall a bad financial decision. However, cleaning their hands with an antiseptic wipe (vs. merely

examining it) attenuated the influence of both kinds of recall. After wiping, those who had

thought about a good decision took less risk, whereas those who had thought about a bad

decision took more risk (Xu, Zwick, & Schwarz, 2012, Study 1).

In a related study, Hong Kong students played a gambling task in which they had good or

bad luck. Subsequently, they were offered the opportunity to play an additional round with their

own money. Those who had experienced a winning streak invested more of their money than

those who had experienced a losing streak. However, washing their hands eliminated the

26

influence of their previous good or bad luck such that winners and losers no longer differed in

how much money they bet (Study 2). Similarly, people who had good luck in four rounds of a

color-guessing game were less likely to want to play the game again after washing their hands

(Moscatiello & Nagel, 2014, Studies 1 & 2). In contrast, those who had bad luck were more

likely to play the game again after washing (Study 2). Across these studies, participants acted as

if good or bad luck left a physical trace that could be wiped off, limiting the impact of one’s luck

on future outcomes.

Endowment

When people sell a product, they ask for more money than they would be willing to

spend to acquire the product (Kahneman, Knetsch, & Thaler, 1991). This so-called endowment

effect appears to be eliminated through physical cleansing. People who washed their hands (vs.

evaluated a liquid soap) were more likely to exchange a previously endowed chocolate bar for a

different one (Florack et al., 2014, Study 2). Similarly, people who washed their hands (vs. had

their height measured) were more likely to exchange a previously endowed drink for a different

one (Study 1), reported better mood, and evaluated both drinks as more positive (but not negative

or acceptable; Study 3).

Goals

Cleansing has also been found to change basic goal priming effects. After unscrambling

sentences containing words related to the goal of academic achievement, people who used (vs.

examined) an antiseptic wipe completed fewer word fragments about the primed goal (academic

achievement) but more word fragments about a conflicting goal (socializing), whereas their

completions pertaining to an unrelated goal (kindness) remained unaffected (Dong & Lee, 2016,

Study 1). This pattern suggests that cleansing can reduce the accessibility of the goal that is

27

active at the time of cleansing.

Because accessible goals guide behavior, cleansing’s effect on accessibility can also

influence active goal pursuit. After unscrambling sentences containing words related to the goal

of being healthy, people who used (vs. examined) an antiseptic wipe were less likely to choose a

healthy granola bar over an unhealthy chocolate bar (Study 2). But if people unscrambled

sentences containing neutral words (i.e., words not priming a health goal), using (vs. examining)

an antiseptic wipe did not influence their snack choices.

Finally, active goals suppress competing goals. If cleansing reduces the accessibility of

an active goal, it may wipe the slate clean for subsequent goals to exert stronger influence.

Indeed, in addition to diminishing effects of goals primed beforehand, cleansing amplifies effects

of goals primed afterwards. If people unscrambled sentences containing words related to one

goal (e.g., health) before a cleansing manipulation and also unscrambled sentences containing

words related to another goal (e.g., saving) after the cleansing manipulation, then using (vs.

examining) an antiseptic wipe decreased people’s judged importance of the previously primed

goal and increased their judged importance of the subsequently primed goal, whatever the goal

contents were (Study 3). This contrastive pattern completely vanished once another manipulation

had psychologically separated a primed goal from the present self (Study 4). By the logic of

moderation of process (Spencer, Zannna, & Fong, 2005), these findings suggest that cleansing is

functionally similar to a procedure of psychological separation.

Summary

Cleansing reduces the influence of recent prior experience, be it negative (e.g., guilt from

immoral behavior, dissonance from free choice, pessimism from academic failure, tension from

physical threat, risk aversion from bad luck) or positive (e.g., moral behavior, good luck, product

28

endowment, primed goals). Cleansing seems to amplify the influence of subsequent experience

(e.g., a new goal) as well. Just how broad are clean-slate effects? They appear valence- and

content-general. We have yet to find domains where cleansing does not exert any influence. To

identify the boundary of clean-slate effects, we need to understand the underlying mechanism.

Physical Cleansing as an Embodied Procedure of Psychological Separation

Because cleanliness effects extend far beyond the moral realm, the embodied metaphor of

moral cleanliness (Lakoff & Johnson, 1999; Landau, Meier, & Keefer, 2010; Williams, Huang,

& Bargh, 2009) cannot be the only mechanism at work. After all, it can only predict clean-moral

effects, but not the full range of clean-slate effects.

We propose that physical cleansing functions as an embodied procedure of psychological

separation (Dong & Lee, 2016). By separating physical traces from a physical target object (e.g.,

detaching dirt from hands), physical cleansing serves as the embodied grounding for the

separation of psychological traces from a psychological target object (e.g., dissociating goals

from the self). As a procedure, separation is content-neutral and applicable across domains,

hence the valence- and domain-general nature of clean-slate effects. Psychological separation, by

marking what belongs to a category and what does not, may even be such a basic component of

cognitive processing that it serves as a deeper basis of the supposedly “basic metaphor” (Schnall,

2014) of moral cleanliness.

What sorts of psychological separation may be conferred by a sense of cleanliness?

Psychological research in several areas can shed some light on different processes that may

underlie cleansing and that predict different boundary conditions of clean-slate effects. For

example, does cleansing work by affectively neutralizing prior experiences? This speculation is

compatible with the observation that washing behaviors appear to trigger termination signals in

29

the security motivational system (Szechtman & Woody, 2004). It is also compatible with studies

in which cleansing reduces the impact of affective (emotional or motivational) experiences, such

as guilt, dissonance, failure, luck, or goal pursuit. If true, this account predicts that cleansing

effects should be limited to affective experiences and should not extend to non-affective domains

(e.g., declarative memory).

Another possibility is that cleansing exerts its influence by distancing one’s prior

experience from one’s present self. Based on research showing that self-distancing enhances

reappraisals of affective experiences (Kross, Ayduk, & Mischel, 2005) and that greater

psychological distance leads to more abstract construal (Trope & Liberman, 2003, 2010), we

expect that if cleansing works through a distancing process, it should enhance not just

reappraisals of affective experiences, but also abstract construals of both affective and non-

affective experiences. Digging deeper, if cleansing does promote distancing, how does it do so?

By functioning as a temporal marker that separates the past from the present (for research on

temporal markers, see Dai, Milkman, & Riis, 2015; Zauberman, Levav, Diehl, & Bhargave,

2009)? If so, clean-slate effects should be mediated by temporal distancing and one may expect

that cleansing reduces the accessibility, clarity, vividness, and concreteness of mental

representations of past events. One may also expect that cleansing changes the construal of past

events such that they seem less spatially near, less socially related, and less causally linked to the

present self.

Or does physical cleansing work by imposing a category boundary that excludes a prior

experience from the construal of the present reality such that people use the former as a standard

for evaluating the latter (Schwarz & Bless, 1992)? If so, clean-slate effects would be mediated by

a comparative process of subjective construal, which should influence not just the accessibility,

30

but also the relevance and use of information.

These deeper mechanisms, their relative contributions, and the boundary conditions they

predict await empirical testing. Teasing them apart will reveal the underpinnings of cleansing as

an embodied procedure of psychological separation. It may provide insights into why cleanliness

and purification are linked to taboo and dangerous things from which we want to separate

ourselves as Douglas (1966) observed in her pioneering work. It may also shed light on medical

practitioners’ common failure to wash their hands (Pittet et al., 2004), thereby pointing to more

effective psychological approaches to nudging this behavioral problem (Griffing, 2012) and

reducing health risks in society.

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