My guess would be that cautious people are more likely to wear masks in the first place, and this would explain the correlation you've noticed between mask-wear

My guess would be that cautious people are more likely to wear masks in the first place, and this would explain the correlation you've noticed between mask-wearing and being cautious. But I don't know for sure. Perhaps mask-wearing also makes uncautious people become more cautious, but I haven't seen anything to support that.