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Related Concept Videos

Bystander Effect02:09

Bystander Effect

10.0K
The discussion of bullying highlights the problem of witnesses not intervening to help a victim. This is a common occurrence, as the following well-publicized event demonstrates. In 1964, in Queens, New York, a 19-year-old woman named Kitty Genovese was attacked by a person with a knife near the back entrance to her apartment building and again in the hallway inside her apartment building. When the attack occurred, she screamed for help numerous times and eventually died from her stab wounds.
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Related Experiment Video

Updated: Dec 9, 2025

Peering into the Dynamics of Social Interactions: Measuring Play Fighting in Rats
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Peering into the Dynamics of Social Interactions: Measuring Play Fighting in Rats

Published on: January 18, 2013

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The bystander effect in rats.

John L Havlik1, Yuri Y Vieira Sugano1, Maura Clement Jacobi2

  • 1Department of Neurobiology, University of Chicago, Chicago, IL 60637, USA.

Science Advances
|September 14, 2020
PubMed
Summary
This summary is machine-generated.

The bystander effect in rats shows similarities to humans. Helping behavior is influenced by the presence and familiarity of other rats, suggesting non-independent actions in social contexts.

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Area of Science:

  • Comparative psychology
  • Animal behavior
  • Social neuroscience

Background:

  • The classic bystander effect, where individuals are less likely to help when others are present, is a well-documented phenomenon in human social psychology.
  • While extensively studied in humans, the universality of this effect across species, particularly in non-primate mammals, remains largely unexplored.

Purpose of the Study:

  • To investigate the presence and characteristics of the bystander effect in rats (Rattus norvegicus).
  • To determine if factors such as helper competence and familiarity influence helping behavior in rats.
  • To compare rat helping behavior in the presence of bystanders to human bystander effect paradigms.

Main Methods:

  • Experimental manipulation of helper rat competence using pharmacological agents.
  • Varying the familiarity of bystander rats (same vs. unfamiliar strain).
  • Observing helping behavior in individual rats and in small groups (duos and trios).
  • Assessing helping rates under different bystander conditions and after observational learning.

Main Results:

  • Rats were less likely to help when bystanders were pharmacologically rendered incompetent, primarily due to reduced reinforcement, not lack of interest.
  • Detrimental effects on helping were observed only when incompetent bystanders were from a familiar strain.
  • Helping rates were near control levels with unfamiliar incompetent bystanders.
  • Group testing (duos, trios) showed superadditive helping rates, indicating non-independent action and facilitation by competent bystanders.
  • Prior observation of helping behavior enhanced subsequent individual helping.

Conclusions:

  • The study provides evidence for a bystander effect in rats that shares key characteristics with the human phenomenon.
  • Helping behavior in rats is modulated by the competence and familiarity of bystanders, as well as social context.
  • These findings suggest that the underlying mechanisms of bystander influence on helping behavior may have deeper evolutionary roots than previously assumed.