Our belief in evil influences our feelings about capital punishment, according to Donald Saucier, associate professor of psychology at Kansas State University and Russell Webster at St. Mary's College of Maryland.

They drew their conclusion after about 200 participants were given a summary of a case in which a murderer confessed to his crime. They then asked each participant about his or her support for different types of sentences, such as jail time with community service, jail time with the opportunity for parole, jail time without the possibility for parole and other options.

They then changed the murderer's characteristics to be consistent with stereotypes about evil. These included having the murderer be interested in the occult, taunting neighborhood children and wearing all black. The characteristics also were changed so the murderer was less stereotypically evil. This included having the murderer be relatively quiet, having a family and being interested in camping.

"People who saw the stereotypically evil person versus the non-stereotypically evil person recommended greater sentences," Saucier said. "But, if they believed in pure evil, it didn't matter the characteristics; they were more likely to support the death penalty or life in prison. The belief in pure evil overrode our stereotypically evil person."

This belief helps explain how opinions of others are formed during social interactions and how believing whether a person is "good" or "bad" at his or her core shapes those interactions.

Stalin certainly had no moral equivalence, and he was evil. His inflexibility about any deviation from his wishes meant punishments were extremely harsh.

"We found that as people's beliefs in pure evil increased, they were more likely to support sentences like life in prison without parole and even the death penalty," Saucier said. "We found that this actually happened through our participants perceiving the murderer as a demon and feeling that there was some need for retribution for the murder committed."

Moreover, it may help explain how a court jury or judge is likely to assign punishment for a crime. While a belief in pure evil probably would not prompt a guilty verdict, it may influence the jury's sentence, Saucier said. For example, sentencing in the trials of Boston Marathon bomber Dzhokhar Tsarnaev and Colorado movie theater shooter James Holmes could be influenced by jury members' belief in pure evil.

Saucier said it's likely that life experience more than religion that influences a belief in pure evil. When investigating whether a religious upbringing was linked to a belief in pure evil, researchers found that people's belief in pure evil didn't necessitate a belief in pure good and vice versa.

"This belief may change based on traumas, victimization and the celebrations of human success in our life," Saucier said. "We think it's a dynamic variable and influences our social interaction and social perceptions."

Saucier is next going to look at how people who believe in pure evil and people who believe in pure good would punish the leaders of the Islamic State group.

Citation: "Demons are everywhere: The effects of belief in pure evil, demonization, and retribution on punishing criminal perpetrators," Personality and Individual Differences.