Psychology pioneer Solomon Asch demonstrated how the desire to "fit in" can change personal behavior under peer pressure. His theory is nicely demonstrated in this 1960's episode of Candid Camera.
https://www.youtube.com/watch?v=GNI5jNBFFT8&ab_channel=NikosKaranikolas
OP: Thank you for all the wonderful comments. You have inspired me to film my own elevator experiment: My cohorts board elevator, subject walks in, door closes, and we all remove masks with an audible sigh of relief and see what happens. Any ideas to spice this up?
Stanford Study Results: Facemasks are Ineffective to Block Transmission of COVID-19 and Actually Can Cause Health Deterioration and Premature Death April 19, 2021, 10:00am
https://www.thegatewaypundit.com/2021/04/stanford-study-results-facemasks-ineffective-block-transmission-covid-19-actually-can-cause-health-deterioration-premature-death/
Show them this while coughing on them. Then tell them Here you wear it!