NCSU Course ZO410 Lecture:
Aggressive Behavior

= overt behavior directed at harming or threatening to harm another individual with the goal of gaining some advantage

    HARM:
    ultimate= not conscious intent to harm, but decreases another's fitness to increase own
    proximate= unpleasant, noxious, painful; deprive another of resource, mate

    GOAL
    - intention is necessary for aggresion
    - different from accidental harm

AGONISTIC BEHAVIOR: threat, attack, submission, withdrawal; always involves a winner and a loser (dominant & subordinate)
 

Nature/Nurture Controversy: Is Aggression Learned or Innate?

Innate:
- can breed for aggressive or submissive strains of animals
- Testosterone:
    - males higher T and agg. than females
    -castration reduces agg. levels
    - need T for normal agg. behavior, ***(but within range of 20% of normal to 2X normal= all same)

Learned:
- social isolation/deprivation experiments
- train dogs to be agg. (guard dogs etc)
- humans: children-- excessive punishment or permissiveness= more agg.
- pre-castration experience affects post-castration behaviors

BOTH IMPORTANT

Why/When does Aggression Occur? Benefits of Aggression?

• cost of agg. low to actor
• benefits of agg. are high
• probability of gaining resource without agg. is low
• genetic relatedness between actor and rival is low
• cost to rival is low

Types of Aggression:

2) Intersexual
M to F --why?
F to M --why?

3) Parental
weaning
dispersal

4) Infanticide
too many offspring
lower competition
female can become pregnant again

5) Peer Aggression/ Siblicide
food competition
dominance hierarchy

Other types Aggression:

• Redirected
• Defensive
• Predatory

Costs of Aggressive Behavior:

injury

energy

time

Evolutionarily Stable Strategies (ESS)

Five Phases of an Aggressive Encounter

Rival Responses

Summary

Human Aggression

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