Do masks increase social distancing? 2 papers suggest that wearing a mask increases social distancing. This would be great if it were true as it would add to the protective effects of wearing masks. Unfortunately neither paper is convincing that this will reduce transmission.
1st paper is rigorously done & provides nice methods & details. While it finds a stat. sign. effect of wearing a mask in how far a person waiting in line stood from the mask wearer (or non-wearer) effect was very small: 161.7 cm vs. 152.7 = 9cm.
osf.io/es7kt/
osf.io/es7kt/
We can use recent results on distance vs risk of transmission to assess the crude impact of the effect on risk (fig - I added red/orange lines). It is tiny.
doi.org/10.1016/S0140-…
(Note: some have criticized use of continuous distance analysis in Chu et al)
doi.org/10.1016/S0140-…
(Note: some have criticized use of continuous distance analysis in Chu et al)
2nd study finds larger absolute effects of mask wearing on distance b/w people crossing on sidewalk. No stats were done on this comparison but by eyeball it looks to be significant. But how meaningful are these data?
Passing by people on a sidewalk outside is an extremely low risk event. Transmission occurs following sustained close contact (most contact tracing uses 10-15 min). Passing someone on a sidewalk is at most 1-2 seconds. Would same effect occur in riskier, long duration, contexts?
Thus, while both studies are creative in experimental design, the 2nd chose a setting that is essentially irrelevant for transmission. Replicating study in riskier environments is needed:
Summary: while mask wearing appears to slightly increase adherence to social distancing neither paper provides convincing evidence that this will have measurable effects on transmission. I hope it will, but we need evidence in high risk settings before making strong claims.
As @jeremyfaust has reminded us, we need to critically assess evidence, even if it supports a position we would like to be correct.
