Male stare and citrus smell increase hand washing by 33%

An experiment to increase staff hand washing in hospitals found that a picture of male eyes placed at eye level increased hand washing by 33%. When this was combined with a citrus scent, the increase rose to as much as 50% more staff washing their hands with anti-bacterial gel before entering a patient’s room.

Psychological priming, or ‘nudges’ were used in the pilot study by researchers to determine the potential impact on hand washing – a significant factor in preventing the spread of infection. Nudges are a concept taken from behavioural science; words, images or signs that prompt behaviour in the observer. 

Male eyes had the biggest impact

The eyes that had the greatest impact were male. The most successful motivating eyes had a high level of facial musculature (skin around the eyes) – this can often be perceived as anger or increased threat.

Image: Monash University Gippsland Campus Flickr

The trial was set up in an intensive care unit by researchers at Warwick, Imperial and Florida University. 404 healthcare workers and visitors were observed to see if they washed their hands with hand sanitizer before entering a patient’s room.

In the control group made up of 120 visitors, only 18 people washed their hands (15 %). Men were more likely to skip hand washing – only five out of 54 (9.26 %) washed their hands. However 13 of 66 women washed their hands (19.70 %).

Male or female eyes: A world of difference

Researchers experimented with images of male and female eyes to see which was most successful in encouraging hand washing. Male eyes were found to be more successful showing a 33.3 per cent increase in hand-washing. However when the photograph was of female eyes, only 10 per cent washed their hands.

Despite the eye prompt, men were still less likely to wash their hands compared to women:

  • 21 women were prompted to wash their hands by seeing the male or female eyes compared to only five men.
  • Only one man was motivated by the female eyes to wash his hands.

Professor Vlaev commented on the different reaction to male or female eyes:

‘This may be because male eyes cue different feelings, thoughts, or emotions than female eyes. In many previous studies examining gender differences in exerting social influence more generally, men have been found to exert more influence than women and this may explain the differences seen. However, it is important to clarify the male eyes showed used more facial musculature, often perceived as anger or threat, so this could have influenced the observed individuals.”

160 individuals observed were exposed to a citrus smell. They were more likely than the control group to wash their hands, with 46.9 per cent using the alcohol hand gel dispenser.

Men motivated by lemons

The citrus smell had a greater affect on men. 35 out of 83 males observed washed their hands (42.17 %). Females again were more compliant with 40 out 77 (51.95 %) washing their hands.

‘Based on these preliminary findings, we believe that further research in this area should be performed in order to better determine whether priming interventions could be a powerful tool in encouraging hand-washing to improve infection rates,” added Professor Vlaev.

Further work could look more fully at gender differences in response to priming-based interventions; whether healthcare workers are affected differently than visitors, and whether the impact is strengthened or diluted through repeated exposure.’


Press release

‘Priming’ Hand Hygiene Compliance in Clinical Environments, (Health Psychology)