The noise of a car crash woke john from his afternoon nap. when he looked out his apartment window, he saw several people milling around two smashed cars. he decided not to dial 911 because he assumed someone had already called. john's reaction is an example of

The answer is the Bystander Effect.

The bystander effect occurs when the presence of others discourages an individual from intervening in an emergency situation, they assume someone else has or will help. Social psychologists Bibb Latané and John Darley popularized the concept following the infamous 1964 Kitty Genovese murder in New York City.

answer; paraphrasing;

answer; in the 1950s;