By hiding in toilet cubicles for a new study, psychologists 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 U.S. 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. Don’t worry, both researchers were provided with a “customised wooden bench” for comfort.

They were also equipped with stopwatches. The researchers 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’d hand wash 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. In contrast, 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. 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).