People respond slower (or not at all) to emergency situations in the presence of passive others.
Imagine that you are in a room all alone filling out a questionnaire, and smoke starts coming from under the door. What do you do? If you are like most sane people, you get out... out at least tell someone in charge, and you do this without hesitation. Now imagine the same situation, except that you are not alone, you are with several other people who don't seem to care about the smoke. What do you do now?
When alone, 3/4 people reported the smoke before the experimental period was terminated. The average time to report was 2 minutes of first noticing the smoke.
When two passive confederates were present (two people that were working with the experimenters who were instructed just to act as if nothing was wrong), only 10% of the subjects in this study actually got out of the room or reported what was ostensibly a serious problem. 9 out of 10 of the subject actually kept working on the questionnaire they were given, rubbed their eyes, and waved smoke out of their faces.
A fairly small sample size was used—only 24 subjects. The passivity of the confederates, one can argue, was not common to a similar real-life situation. The combination of many confused people can prompt action. The relaxed and indifferent attitudes of the confederates could have instilled a false sense of security.
At some points in our lives, we all find ourselves in situations where someone needs to take action, but because that "someone" is not specified, nobody takes action. In an emergency situation, instead of yelling "somebody help," we are better off pointing to someone and telling them to go get help. When we are working on a group projects, it is best to assign specific tasks to specific people, rather than just assume someone will "step up."
Don't let the passivity or stupidity of others result in your inaction. Don't assume that someone else will help—take action