Massimo Marchiori, an Italian computer scientist, once used sensors to determine how the widths of shopping mall walkways shaped buying decisions. Another time he used GPS technology to track the movements of cows to see what behaviors led to the best milk.

So when the novel coronavirus consumed Italy in February, Marchiori decided it was time for a new experiment — this time, on social distancing. The result suggested that masks help fight contagion in ways other than just filtering air — benefits rarely discussed in the fraught political conversation about whether mask-wearing in public spaces should be mandatory.