The spread of super-resistant bacteria means the science of hand-washing behaviour has become a serious business. Psychologists have stepped up to the plate. Bowl, I should say. By hiding in toilet cubicles for a new study, they’ve observed how long people spend using the loo, and how long they wash their hands for afterwards. That men usually wash their hands less conscientiously than women is a well-established finding. Thomas Berry and his colleagues wanted to find out more about the reasons for this gender difference.

For one day, between 10am and 4pm, a male researcher secreted himself inside one of three cubicles in a gents toilet facility at a US University. For optimal observational purposes he chose the cubicle adjacent to a row of three urinals. Nearby, in a similarly designed female toilet facility, a single female researcher positioned herself in one of the three cubicles available.

Both researchers were provided with a “customised wooden bench” for comfort and equipped with stopwatches. They used an “unobtrusive sight procedure” – that is, they spied on other visitors to the lavatories using the gaps beneath and by the side of the cubicle doors (for some reason, US toilet cubicles always have a gap of about a centimetre either side of the door). The researchers also used an “acoustic procedure”. That is, they listened to the visitors’ actions. The study authors explained:

“… research assistants recorded the facility [urinal or cubicle], and then started a stopwatch when the patron’s feet stood relatively still. For the men, the research assistants also recorded the orientation of the feet to gauge the patron’s use of the commode (i.e. as a commode or a urinal). When research assistants heard the flushing of the patron’s commode or urinal the stopwatch was turned off … and the duration of the restroom event was recorded.”

Similar procedures were followed for recording each visitor’s “hand washing event” if there was one. A clever twist was that for part of the study, the researchers put “out-of-order” signs over the men’s urinals. This was to see how much they washed their hands if they were forced to urinate in a cubicle, rather than at a urinal.

The psychologists managed to observe the toilet behaviour of 34 women using cubicles; 32 men who used a cubicle to defecate; 40 men who had no choice but to use the cubicles for urinating (because of the out-of-order signs); and 64 men who used a urinal. The bare statistics show that the hand-washing rates for these four groups were 91 per cent, 87.5 per cent, 75 per cent and 59.4 per cent, respectively.

The difference in hand-washing rates between women using a cubicle and men using a cubicle (for defecating) was not statistically significant. Meanwhile, both women using a cubicle, and men using a cubicle (for defecating), showed significantly higher hand-washing rates than men who used a urinal.

The data are somewhat compromised because, as the researchers delicately put it – the women’s “facility use is a constant (i.e., commode) and their behaviour (urination, defecation, or menstrual care) is confounded within the one environment.” However, taken together, the results suggest that the reason men wash their hands less than women overall, is not because of gender norms (i.e. because men are less bothered about being clean), but because of the differences in the toilet environment and toilet behaviour for men and women. In fact, after using a toilet cubicle to defecate, men tended to wash their hands for longer than women (but remember we don’t know what the women had been doing).

This raises a question: do men wash their hands more thoroughly after using a toilet cubicle because of what they’ve usually been doing in there or because they perceive cubicles to be more dirty? This is where the “out of order” signs on the urinals came into play. The researchers wanted to see what percentage of men would wash their hands after using a cubicle to urinate. Unfortunately the results were inconclusive – the hand-wash rate of 75 per cent after using the cubicle for urinating did not differ significantly from the rates after using a cubicle for defecating, or from the rates after using a urinal.

However, another useful comparison was how long men washed their hands after using a cubicle for defecating, after urinating in a cubicle, or after urinating in a urinal. This revealed that men’s duration of hand washing was more closely related to what they’d been doing, than to where they’d been doing it. This suggests public health notices need to use signage and other means to encourage men to wash their hands thoroughly regardless of what they’ve been doing.

In fact, based on this study, members of both genders need more encouragement to wash their hands more diligently. Looking at the median hand washing durations (17.5 seconds for men using cubicles for defecating; less than 10 seconds for women and for men using urinals), both genders were well short of the Centers for Disease Control and Prevention recommendation that we should wash our hands for a minimum of 20 seconds to have any meaningful chance of removing harmful germs.

You might be wondering if it’s ethical for psychologists to lurk about in public loos observing people’s lavatorial habits. Berry’s team argue that it is, given the seriousness of the health issues involved, and so long as patron anonymity is protected, and that their “public-private life was not threatened or intruded upon”.

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Thomas D. Berry, Daniel R. Mitteer, and Angela K. Fournier (2014). Examining Hand-Washing Rates and Durations in Public Restrooms: A Study of Gender Differences Via Personal, Environmental, and Behavioral Determinants. DOI: 10.1177/0013916514527590

—Further reading—

For The Psychologist magazine, Nick Haslam argues that psychologists should stop averting their eyes from the bathroom.

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest