The Macbeth effect

By Johnjoe McFadden, professor of molecular genetics at the University of Surrey (THE GUARDIAN, 01/11/06):

can you wash away your sins? The overlap between the language of morality and personal cleanliness (clean conscience, the stain of original sin) suggests that our soul and the body share an aversion to dirt. Most religions practise some purification ritual – baptism, bathing in the Ganges – where the soul can be washed clean of sin; and Lady Macbeth’s obsessive hand washing (“Out damned spot”) sought to remove the stain of treachery as much from her conscience as from her hand. But would it work? Research by Chen-Bo Zhong and Katie Liljenquist from the University of Toronto and Northwestern University, Chicago, suggests that scrubbing may indeed ease a guilty conscience.

the researchers studied a group of volunteers, half of whom were told to recall a shameful incident and the other half to recall some neutral event. They were then asked to solve anagrams that could be resolved to form either cleaning words (wash, soap) or ethically neutral words (wish, step). The subjects who had to recall the ethically challenging episodes tended to solve the anagrams to form many more cleaning words than the other group. Was this due to an urge from the ethically challenged subjects to cleanse their soiled consciences? To test this, the researchers provided their subjects with a free gift, antiseptic wipes or a pencil. The ethically challenged subjects were twice as likely to choose the wipes.

It seems that physical cleansing allows us to wash away our sins, a phenomenon the researchers dubbed the “Macbeth effect”. We like to believe that we are morally upstanding citizens, and when that self-image is threatened we tend to engage in compensatory behaviour. This may be a good deed but it may also involve a good wash.

In an earlier study, Philip Tetlock and colleagues at the Universities of Ohio and Carnegie Mellon University put forward the Sacred Value-Protection Model (SVPM) that proposes that some of our values can not be bargained away; when these “sacred values” are threatened we engage in compensatory behaviour. In their study they gave Christian students a provocative text such as: “If Joseph had left Mary because he did not believe she had conceived a child with the Holy Ghost, Jesus would have grown up in a one-parent household and formed a different personality.” The most fundamentalist students were far more likely to engage in the moral cleansing activity after having had their sacred values challenged.

Zhong and Liljenquist looked at whether physical cleansing satiated the need for moral cleansing so that their volunteers would be less inclined to engage in more practical moral-restoring activity, such as helping others. After recalling their shameful past the subjects were given the opportunity to wash their hands, before being asked whether they would volunteer for unpaid work to help a penniless student. Some 74% of the still unclean subjects volunteered for the good deed but after a good hand scrub the rate of volunteering dropped to 41%. Zhong and Liljenquist’s research suggests that a good scrubbing may ease our conscience, but it leaves us less inclined towards more practical good deeds.

Is it possible that the effect works at a national or global level? Every day Iraqi civilians are being killed as a direct consequence of UK and US foreign policy but is that easier to bear so long as we cut carbon emissions? Much of the 21st century protest agenda is directed towards keeping the planet clean but maybe this cleansing serves as a communal Macbeth effect that wipes away the “damned spot” of our global sins. Lady Macbeth never did wash away the stain: Shakespeare seems to be saying that sins can’t be washed away so easily.