7 Shocking Psychological Insights Behind the Slenderman Stabbing

Incident Overview: What Happened?

In 2014, two 12-year-old girls in Waukesha, Wisconsin, stabbed their friend 19 times in a park. The attack was brutal and nearly fatal, with wounds affecting vital organs including the heart, diaphragm, liver, and stomach.

What makes this case particularly disturbing is the motive given: the girls believed that the fictional entity known as Slenderman, a tall, faceless supernatural figure from online horror lore, threatened to kill them and their families unless they committed the attack.

This stabbing shocked the world because it combined youthful innocence, dangerous delusions, and the dark power of internet urban legends.

The Role of Shared Delusion

Central to understanding this violent act is the concept of shared delusion, a psychological phenomenon where two or more individuals develop the same false belief together. In this case, both girls convinced themselves that Slenderman was real and posed a deadly threat.

Psychologists testified that shared delusion is rare, especially among children, but when it occurs, it creates a powerful and dangerous bond. The two girls reinforced each other’s fears and twisted reality to fit their narrative.

“She was only 12 years old and deeply influenced by a website filled with fictional killers and boogeymen,” a psychologist explained during the trial.

Why 12-Year-Olds Are Vulnerable

At age 12, the brain is still developing, especially areas responsible for critical thinking and reality testing. This immaturity explains why children at this age struggle to distinguish between fact and fiction, especially when emotionally involved.

The girls’ susceptibility was heightened not only by their developmental stage but also by social isolation and emotional needs, making it easier for fantasy to overtake their grasp on reality.

Internet Myths and Their Psychological Impact

Slenderman originated as a fictional character created for a 2009 internet Photoshop contest, but it quickly evolved into a widespread myth. This myth embraced creepy storytelling, fan art, and horror videos, which fascinated young audiences.

The girls spent hours on websites dedicated to Slenderman and similar horror stories. This constant engagement amplified their belief in the entity and shaped their perception that violence was the only way to appease or avoid Slenderman.

Mental Illness and Psychosis in the Case

One of the girls, Morgan Geyser, was later diagnosed with early onset schizophrenia, marked by delusions and hallucinations that severely impaired her ability to discern reality.

Her mental illness likely exacerbated the shared delusion and the violent outcome. Her defense argued that her psychosis meant she could not be held fully responsible for her actions.

“Her schizophrenia was so severe that this act of savage, irrational violence was all because she was lost in the grip of delusional fantasy,” a forensic psychologist stated.

Social Pressure and Loyalty

The dynamic between the two girls was critical. They were close friends, and the desire to maintain this bond contributed to their participation in the stabbing plot.

Legal arguments pointed out that while one girl carried out the attack, the other was complicit, arguably influenced by friendship loyalty and fear of losing her friend if she refused to join.

Media Effect and Information Literacy

This case exposes a profound lesson about information literacy — the ability to critically evaluate and understand the information consumed, especially online.

Young people encountering horror myths and dark internet content without guidance or critical thinking skills are vulnerable to misunderstanding fiction as reality.

The Slenderman stabbing thus serves as a cautionary tale about the psychological impact of viral myths on youth and the responsibility of media consumers, parents, and educators to nurture healthy skepticism.