A social psychological phenomenon concerning people’s likeliness to help in an emergency situation. According to the Bystander Effect, the greater the number of other people present when the emergency occurs, the less likely any one of them are to help. The 1964 Kitty Genovese murder case in New York City, where multiple bystanders heard or saw a young woman being stabbed to death and did nothing to assist her, is an oft-cited example of the Bystander Effect at work.
So why do people tend to behave like this? Well there are two reasons that seem to jump out…one, when you are in a crowd you automatically assume that someone has done something or will eventually make the call. Two, no one wants to be the person who is behaving differently…if no one is reporting it, clearly it is not socially acceptable. This is an incredibly interesting behavioral pattern.
Here is a link to an article about the Kirry Genovese murder: http://psychology.about.com/gi/o.htm?zi=1/XJ&zTi=1&sdn=psychology&cdn=education&tm=422&gps=643_634_1238_766&f=00&su=p897.9.336.ip_&tt=2&bt=1&bts=1&zu=http%3A//kewgardenshistory.com/ss-lefferts-1100.html