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Published on: June 10, 2013
Maternal defense: breast feeding increases aggression by reducing stress.
Jennifer Hahn-Holbrook1, Julianne Holt-Lunstad, Colin Holbrook
1Department of Psychology, University of California, Los Angeles, CA 90095, USA. jhahn@psych.ucla.edu
Breast-feeding mothers show increased aggression to protect their infants. Lactation may reduce stress responses, disinhibiting this protective maternal aggression.
Area of Science:
- Evolutionary biology
- Neuroscience
- Human behavior
Background:
- Maternal aggression is common in mammals for offspring protection.
- Lactation in nonhuman mammals is linked to heightened aggression.
- This suggests a potential parallel in human mothers during breastfeeding.
Purpose of the Study:
- To investigate if lactating humans exhibit heightened aggression.
- To explore the physiological mechanisms underlying maternal aggression.
Main Methods:
- Behavioral experiment comparing aggression levels in lactating, formula-feeding, and never-pregnant women.
- Measurement of punitive sound bursts as an indicator of aggression.
- Monitoring of systolic blood pressure during aggressive responses.
Main Results:
- Breast-feeding mothers displayed significantly louder and longer punitive sound bursts compared to other groups.
- Lactating women showed lower systolic blood pressure while aggressing.
- Mediation analysis suggested reduced arousal during lactation disinhibits aggression.
Conclusions:
- This study provides the first behavioral evidence for heightened aggression in lactating humans.
- Lactation may buffer maternal stress responses, facilitating protective aggression.
- Breastfeeding contributes to infant protection and maternal stress buffering.
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