When communicating about coronavirus, policymakers face a delicate balancing act: sharing enough information that people know what to do, but not so much that it becomes overwhelming. How much information is too much?
To answer this question we ran a randomised controlled trial (RCT) in Bangladesh on good handwashing technique, which as we all now know is an important way of reducing COVID transmission.
Thanks to the hard work of our partners at BRAC, and our funders at DFID and Unilever, 1,000 public handwashing stations are being installed at busy locations across Bangladesh, such as outside mosques, markets and bus stands. Each station consists of three sinks and has a message board behind, on which BRAC will place instructional posters to encourage thorough handwashing.
Fig 1. An early image of the construction of the first public handwashing station. Posters will be placed on the message board immediately above the sinks.
In our trial, we randomly showed one of four potential poster designs that would be used on the message boards (or a no-poster control). We tested 2,196 adults in Bangladesh, recruited via social media, on their ability to recall and understand key messages from the posters.
The posters varied in the amount of handwashing guidance:
- Poster A was the original design. It contained instructions on how to operate the station, followed by the message to wash your hands with soap for at least 20 seconds.
- Poster B presented similar guidance but with the handwashing message becoming the focus of the poster and repositioned to the top, with instructions on how to use the foot pumps at the bottom.
- Poster C added 4 key handwashing steps (wash your palms, thumbs, in between your fingers, and the tips of your fingers), presented using bright infographics and minimal text.
- Poster D added 3 further handwashing steps (wash your wrists, the backs of your hands and the backs of your fingers) to present a more comprehensive guide to handwashing technique.
We found that step-by-step guides improved recall of handwashing steps, but too many additional details obscured the main handwashing messages.
After seeing either the 4-step or 7-step poster, people were approximately 10 percentage points more likely to recall that they need to wash their palms and wash their thumbs compared to the posters that contain only the simple messages (83% recalled for palms and 68% recalled for thumbs, up from 73% and 59% respectively in the posters without step-by-step guides). Whilst it’s hard to imagine washing your hands without washing your palms, many people forget about their thumbs, so this increase could lead to a meaningful improvement in technique.
However, in the case of the longer 7-step poster that improvement comes at a cost. For the 7-step poster, people are 5 percentage points less likely to recall that they should wash their hands for at least 20 seconds compared to the “Simple + BI” poster (92%, down from 97%). This is a case of ‘too much information’: the extra detail causes some people to miss the most basic message of the posters.
What were the limitations of this online trial?
At the start of July we could not safely ask enumerators to show participants the posters in person. We were therefore forced to recruit survey participants online (in this case, through Facebook adverts). This sample will be different from our target population of those likely to use the public handwashing stations.
To translate the trial results into practical recommendations for the handwashing stations, we need to think about how differences between our trial sample and target population might affect understanding. For instance, a proportion of our target population has low literacy levels, unlike our trial sample which is more highly educated.
We believe this strengthens the argument for the step-by-step posters, because they contain visual images of handwashing techniques, as opposed to the simple posters which contain only written instructions. In addition, information overload may be more of a concern for individuals with lower levels of education, which strengthens the argument against adopting the longer step-by-step poster.
For both reasons, we believe that the case for a short step-by-step guide is even stronger in our target population. If you would like to read more, the full results from the trial are available here.
What next for the handwashing stations?
We believe that the results of this RCT have led to a poster design that is more likely to encourage thorough handwashing amongst our target population in Bangladesh. The 4-step poster appears to strike a balance: it improves understanding of handwashing techniques without worsening recall of the simple message to wash hands for 20 seconds. BRAC have used the 4-step poster in the initial set of 20 pilot handwashing stations and will be collecting user feedback to see how it fares in the real world.
We’re very excited about this approach more generally – adding some empiricism to intervention designs, even under tight time pressure. This approach requires partners such as BRAC, Unilever and DFID who see the value of research to inform the design of programmes. Testing the fine details of an intervention at an early stage allows better designs to be scaled up.