When most people hear about serial killers, they automatically think that they are a horrible person who just enjoys killing people. In reality, there is so much more to them that people don't understand. Research on serial killers dates back to the early 1900s. There has also been a lot of statistical information that has been learned about them, which would give you the percentages of how many serial killers have gone there to some times, places even which race has the most serial killers. Some of the information I learned was about why serial killers enjoy killing, the differences between male and female serial killers, and statistical information about their race, IQ, and why the United States has by far had more serial killers than any other country. Over the years, there have been many theories about why hit men kill, and which crimes have a lot to do with their childhoods. A typical boy's childhood would be going to school and playing with friends. It's pretty much the opposite for a serial killer. Many studies have been done on the childhoods of serial killers and how they were treated by their family members. ***http://listverse.com/2013/01/02/10-most-common-traits-of-potential-serial-killers/ has compiled a list of the 10 most common traits of serial killers when they were children. . Of the 10, the first 3 are physical injuries, acting out fantasies about animals, preference for autoerotic activities. Few people would think that head injections would cause a person to act or think a certain way, but this is the case for approximately 70% of all serial killers who have suffered some type of head trauma to the head. during their childhood or adolescence. A part of the brain that is sometimes affected by severe head trauma is the limbic brain. The limbic system is the part of the brain that differentiates between female and male serial killers and their victims. Women largely tend to kill victims they know and are close to (Geringer, 2). This could range from family members to someone they care for, such as a nurse or caregiver. For the most part, the men do not have a relationship with their victims (Geringer, 2). They will choose a stranger and hunt him down until he is ready to commit his crime (Geringer, 2). That being said, you would think that it would be harder to detect men since the victims are random, but the extent of their crimes easily gives them away.*** SIMILARITIES Although male and female serial killers seem very different , there are three major similarities. . The first is their ability to present themselves as normal-looking citizens. Most of society assumes that all serial killers look like Hannibal Lecter (Geringer, 2).