People see that others are in an emergency situation and do not go to rescue, not because of the loss of humanity, but because the presence of other people reduces their sense of responsibility, thereby inhibiting people's motivation to rescue. This kind of responsibility distraction, also known as onlooker effect of the individual. The responsibility of the individual becomes unclear, thus the sense of responsibility is diluted, and things eventually happen in a way that no one thinks will happen. Because of the proliferation of responsibility, the crimes caused by not doing justice and failing to save,   the feelings of guilt will also spread to other people. The risk of a person's moral evaluation is greatly reduced, and the moral condemnation he feels is also greatly reduced, so that it is entirely possible to adopt the same attitude and behavior in the next similar situation.
mainly introduced?
The psychological mechanism of the onlooker effect.