A father figure is usually an older man, normally one with power, authority, or strength, with whom one can identify with on a deeply psychological level and who generates emotions generally felt towards one's father. Despite the literal term "father", a father figure is not limited to the biological parent of a person, especially a child. Studies have shown that a lack of a father figure in a child's life can have severe negative psychological impacts upon a child's personality and psychology. Many infamous serial killers such as Jeffrey Dahmer and John Wayne Gacy have backgrounds of extreme abuse, or simply no recognition, during their childhood from their fathers. Positive father figures have a significant role in a child's development. Under the circumstances of child abuse and neglect, it is not uncommon for a child to seek out a parental figure as a substitute/proxy for the deficit of love and care at home. These "proxies" in children's cases are used to fulfill the need and want of a parent who can protect them from harm, which is usually driven by an unconscious need for safety and a defective Oedipus Complex. Unfortunately, many sexual assault cases have been linked to this kind of behavior, which can lead to fatal obsession and possessiveness. Several studies have suggested that positive father figures, whether biological fathers or others, are generally associated with healthy child development.