In diffusion of responsibility, a person who is alone is more likely to act in an emergency.
In a group, the individual will often assume someone else will take action. "In an unfamiliar and strange situation … taking action is challenging," Staub said. "You have to step forward and expose yourself to public scrutiny."
Research has also shown that when a person is in a position of leadership or specific role, they are more likely to act.
In pluralistic ignorance, individuals privately reject the group, but are afraid to speak out.
"People don't show their emotions in public," he said. "They kind of put on a poker face or wait for others' reactions. As they look around and see others don't react, they decide not to react."
In studies of children in kindergarten to sixth-grade, Staub found that the youngest children "naturally say something" when they heard a "crash and distress" in a neighboring classroom, eliminating pluralistic ignorance.
"It causes attention and kids engage in a discussion and move jointly to some kind of action," he said. "By second grade, that disappears."
More research of children in the seventh-grade has shown that those who are given permission "for an irrelevant reason" to go into another classroom are more likely to respond if they hear distress.
Those with no instruction from teachers responded only 30 percent of the time. In those who were told they could leave the room, 90 percent reacted to the "emergency."
"Kids learn all kinds of rules of everyday behavior that inhibit them from helping people," Staub said. "They don't learn that under certain conditions, moral or caring rules override the rules of every- day behavior."
"I wonder if the same thing is present in the medical profession?" he asked. "There are all kinds of implicit rules: Don't interfere, it's another's domain."
While teaching a class at Stanford, Staub asked students where it was better to take action when it is uncertain whether it was needed.
"The worst that could happen was that it was not needed," he said. "The undergrads said basically they prefer no action so as not to expose themselves to embarrassment.
"People have powerful influence over each other," he said. "It's not just the presence of others, but what others say. They define the meaning of the situation and the appropriate action. We look to others for cues."
E. Scott Geller, director of the Center for Applied Behavioral Systems at Virginia Tech University and author of a book about medical errors, "Actively Caring For People," said the "bystander effect" does influence medical decisions.
"We are so busy these days that if we can pass the personal responsibility off to someone else, we are going to do it, especially if it seems justified," Geller said. "One way to decrease the bystander effect is to make sure responsibility is assigned."
In studies of a phenomenon known as "social loafing," researchers found that when measured, individuals in a rope contest would pull harder than when in a group.
When pulling alongside another, a person thinks, "They got my back," he said. "If I think you are going to hold me accountable for how I contribute, then I am going to hold up my weight."
The issue of competence also comes into play in the medical world, Geller said.
"If the observer knows what to do, you don't get the bystander effect," he said. "In this medical example [from Yale], it seems there were so many unknowns."