In the social media era, stereotyping can lead to fraught encounters that go viral: In recent weeks, people have called the police on innocent black people for doing nothing more than waiting at a Starbucks cafe or napping in a dorm.

The social psychologist Claude Steele’s 2010 book “Whistling Vivaldi” examines stereotype threats — predicaments in which people worry that others are judging them solely because of their race or gender or age. He found that racial stereotypes hindered the academic performance of black children and contributed to persistent segregation.

We wanted to understand more about these encounters.

We asked readers to share stories — often, painful ones — of times that they have made unjust assumptions about others. We asked readers to tell us what role race played in their thinking, how their thoughts affected their behavior, and what they would do differently.

We received nearly 200 responses — many of which described times in which racial stereotypes led to mistakes, misunderstanding and on some occasions, false police reports. Here are a few , condensed and edited for clarity .