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Bystanders Are the Majority — Reading Bullying Beyond the Bully-Victim Frame

By Leon MoriguchiPublished May 15, 2026Updated May 18, 20267 min read日本語版あり
Audience
Parents of primary-school-age children

TL;DR

  • ·Bullying is a group phenomenon, not a two-person problem: Salmivalli's participant role research found that outsiders — those who knew but did not act — form the single largest group in a classroom, making informed non-involvement the statistically normal position
  • ·Reinforcers and assistants sustain bullying without touching the victim — laughter, filming, gathering to watch all contribute to structuring the behavior as a performance that the perpetrator is sustained by, not incidental to
  • ·The KiVa program's RCT demonstrated that targeting the bystander layer — rather than focusing only on the perpetrator — produced a 35–50% reduction in victimization rates, confirming that the bystander is where the leverage actually lives

Contents

  1. Lead
  2. Bullying as a Group Phenomenon
  3. Salmivalli's Six Roles
  4. What Reinforcers and Assistants Actually Do
  5. The Defender
  6. What the KiVa Program Demonstrated
  7. Signs Families Can Watch For
  8. The Limits of Home Involvement, and Working with the School
  9. From Structure to Action
  10. Summary
  11. References

Lead

"My child isn't the one doing the bullying" — that statement is probably accurate in most cases. Perpetrators are a minority. So are direct victims. The question is how to think about the much larger layer in between.

What decades of bullying research have established is not a two-person relationship between aggressor and victim but a map of roles distributed across a classroom functioning as a social system. Perpetrators are necessary for bullying to occur, but what sustains it — laughter, attention, silence — is a broader collective dynamic. That finding has been reproduced across longitudinal studies and school-based surveys for years [1,2].

This article uses the participant role theory developed by Finnish developmental psychologist Christina Salmivalli as its organizing framework. Easy prescriptions are not on offer. But understanding the structure changes the questions worth asking.

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