Over the course of the SARS-CoV-2 outbreak, strict lockdown policies have proved effective in slowing down the spread of the virus. In many countries, including heavily affected regions in Italy, France, and China, the number of newly infected cases per day has decreased substantially since the height of the pandemic in March and April 2020. While countries are slowly opening up to allow for economic and social activity to resume, politicians and citizens wonder which measures to take to prevent a second wave. It appears uncontroversial that the physical distancing recommendation and personal hygiene recommendations are here to stay. In contrast, the universal use of face masks is highly debated.

Several studies suggest that face masks, particularly if adopted universally, can be of high value in preventing further spread of SARS-CoV-2 (Chernozhukov et al., 2020; Eikenberry et al., 2020; Leung et al, 2020). Nonetheless, not all public health authorities endorse the preventive use of face masks in the public. For example, Danish, Norwegian, and Swiss authorities are decidedly not recommending their use by healthy individuals. One main argument against making the use of face masks mandatory in public spaces is based on the idea of risk compensation. If face masks offer some protection against the spread of the virus, they may give individuals a false sense of security and lead them to be less cautious in other dimensions, for example with respect to keeping a safe distance from others and complying with social distancing rules. While this argument features prominently in the public debate (e.g., WHO, 2020), whether people indeed risk compensate in response to masking or not is an empirical question that has not been rigorously tested.

Seres et al. (2020) contribute to this debate with results from a field experiment that was conducted in Berlin in April 2020. Waiting in line outside to enter a business, the experimenter varied whether or not to wear a mask and, in each condition, recorded the distance subjects entering the line behind him or her came to a stand. Contrary to the risk compensation hypothesis, the study finds that subjects stay significantly further away from the experimenter when he or she is wearing a face mask than when he or she is unmasked. Further, additional survey results indicate that people believe someone wearing a face mask would like others to keep a safe distance from him or her, a preference that is responded to with a larger distance.

These findings have important implications for the discussion of face covering. In particular, the study suggests that individuals will not let down their guard when someone else is wearing a mask. To the contrary, masks may foster efforts to comply with the recommendation of physical distancing. While the observed positive effect may decrease under compulsory masking because the signal value of desired distances is weakened, the evidence speaks strongly against a supposed harmful negative effect of masks on physical distancing. Of course, there are other aspects in this debate that are important but to which this study cannot speak, for example, whether or not masking has negative side effects on health or infection risk to the wearer (Greenhalgh, 2020; Greenhalgh et al., 2020; Lazzarino et al., 2020).

Jana Friedrichsen (HU Berlin and WZB Berlin)
Yiming Liu (HU Berlin)

Chernozhukov, V., Kasaha, H., & Schrimpf, P. (2020). Causal impact of masks, policies, behavior on early Covid-19 pandemic in the US. arXiv preprint arXiv:2005.14168.

Eikenberry, S. E., Mancuso, M., Iboi, E., Phan, T., Eikenberry, K., Kuang, Y., ... & Gumel, A. B. (2020). To mask or not to mask: Modeling the potential for face mask use by the general public to curtail the COVID-19 pandemic. Infectious Disease Modelling.

Greenhalgh, T. (2020). Face coverings for the public: Laying straw men to rest. Journal of Evaluation in Clinical Practice, e13415. 

Greenhalgh, T., Schmid, M. B., Czypionka, T., Bassler, D., & Gruer, L. (2020). Face masks for the public during the covid-19 crisis. Bmj, 369. 

Lazzarino, A. I., Steptoe, A., Hamer, M., & Michie, S. (2020). Covid-19: Covid-19: Important potential side effects of wearing face masks that we should bear in mind [electronic response to Greenhalgh et al. Face masks for the public during the covid-19 crisis]. Bmj, 369. 

Leung, N. H., Chu, D. K., Shiu, E. Y., Chan, K. H., McDevitt, J. J., Hau, B. J., ... & Seto, W. H. (2020). Respiratory virus shedding in exhaled breath and efficacy of face masks. Nature Medicine, 26(5), 676-680.

Seres, G., Balleyer, A. H., Cerutti, N., Danilov, A., Friedrichsen, J., Liu, Y., & Süer, M. (2020, May 23). Face Masks Increase Compliance with Physical Distancing Recommendations During the COVID-19 Pandemic. Retrieved from https://osf.io/db8sj/.

WHO (2020). Rational use of personal protective equipment for coronavirus disease (COVID-19) and considerations during severe shortages. Interim guidance, April 2020, WHO Reference Number: WHO/2019-nCov/IPC_PPE_use/2020.3.