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Updated: Sep 27, 2025
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The Resident-intruder Paradigm: A Standardized Test for Aggression, Violence and Social Stress
Published on: July 4, 2013
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Introduction to defensive behavior in vertebrates.
Giancarlo Carli1, Francesca Farabollini1
1Department of Medicine, Surgery and Neuroscience, University of Siena, Siena, Italy.
Progress in Brain Research
|April 10, 2022
Summary
Defensive behaviors, including tonic immobility (TI), are activated by threats. Passive immobility, like TI, is adopted when escape is not possible, influenced by context and proximity to danger.
Area of Science:
- Ethology
- Animal Behavior
- Neuroscience
Background:
- Defensive behaviors are crucial for survival.
- These behaviors are influenced by threat distance and context (escapable/inescapable).
- Passive immobility, including tonic immobility (TI), serves as a substitute for active escape.
Purpose of the Study:
- To describe the ethological basis of defensive behaviors.
- To explain the role of tonic immobility (TI) within the defensive repertoire.
- To explore the influence of context and animal personality on defensive strategies.
Main Methods:
- Review of ethological principles governing defensive behaviors.
- Analysis of factors influencing the activation of defensive strategies.
- Examination of tonic immobility (TI) induction, particularly under physical restraint.
Main Results:
- Defensive behaviors form a system influenced by threat distance and context.
- Passive immobility, including TI, is adopted in inescapable situations or close proximity to threats.
- Animal personality affects coping mechanisms, with TI potentially being a behavioral syndrome trait.
Conclusions:
- Tonic immobility (TI) is a key passive defensive behavior.
- Context, threat proximity, and individual differences (animal personality) shape defensive responses.
- TI can be considered a behavioral trait in mammals and avians.
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