Fear of strangers

Why are we more likely to take off our masks or avoid social distancing with a group of friends at a party instead of strangers on the train?

Why do we drive more carefully in a new neighborhood instead of near our home?

Why trust the advice of a doctor who looks like us, or went to the same school we did?

Our evolved preference for familiarity often backfires. There are many signals that give us useful information about whether a situation is productive or safe. But pre-existing social networks might not be the best one.