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We ’ ve established the fact that Eavesdropping is common... - PowerPoint PPT Presentation


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We ’ ve established the fact that Eavesdropping is common... … this paves the way for modifying other games we ’ ve already discussed. COOPERATION. HAWK-DOVE. COOPERATION. Direct Reciprocity– “ I scratch your back you scratch mine ”

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We ’ ve established the fact that Eavesdropping is common...

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We’ve established the fact that Eavesdropping is common...

… this paves the way for modifying other games we’ve already discussed

COOPERATION

HAWK-DOVE


COOPERATION

Direct Reciprocity– “I scratch your back you scratch mine”

Indirect Reciprocity – one does not expect return from the recipient

but from someone else - “Give, and you shall be given”

Indirect Reciprocity involves reputation and status;

individuals are continually assessed and reassessed


Evolution of indirect reciprocity by image scoring – Nowak and Sigmund 1998

  • Cooperation includes benefits and costs

  • If donor cooperates image score increases; if not it decreases

  • Image score is honest and perfect public information

  • Pure Discerning cooperation evolves – cooperate with

    everyone with a image score > 0

  • Requires : p >c/b – the probability of knowing the image

    score (p) of the recipient must exceed c:b ratio

  • Group size effect: groups of 20 cooperate; whereas rare

    for groups of 100 (imperfect information)


  • Group size effect: groups of 20 cooperate

  • whereas rare for groups of 100 (imperfect information)


Evolution of indirect reciprocity by image scoring – Nowak and Sigmund 1998

  • Cooperation includes benefits and costs

  • If donor cooperates image score increases; if not it decreases

  • Image score is honest and perfect public information

  • Pure Discerning cooperation evolves – cooperate with

    everyone with a image score > 0

  • Requires : p >c/b – the probability of knowing the image

    score (p) of the recipient must exceed c:b ratio

  • Group size effect: groups of 20 cooperate; whereas rare

    for groups of 100 (imperfect information)

COOPERATION EVOLVES W/O DIRECT RECIPROCITY

NO GOOD ACT SHOULD GO UNDISPLAYED


But does image scoring really

occur?


  • 2000 interactions/day w/queue

  • Eat parasites (coop) & mucosal

  • tissue/scales (defect)

  • The latter leads to client “jolt”

  • so an observable cue


  • Jolts are predictors:

  • 12-18/min among biting cleaners

  • 2-3/min among coop cleaners

  • Do clients image score?

  • If previous client ends w/conflict (jolt/chasing):

  • 100% bystanders (queue) depart

  • w/o conflict 100% approach

  • Audience effects?

  • 17 vs. 6 cleaners spp showed (-) relationship

  • between jolts and bystander presence

  • And also observed in Sergeant major


HAWK-DOVE – Johnstone 2001

Eavesdropping as a new strategy to play H-D games

  • Play Hawk when you observed your opponent losing

  • Play Dove when you observed opponent winning

  • Hawk-Dove-Eavesdrop is a mixed strategyESS

    It does well when rare by anticipating other individual’s behavior;

    but cannot anticipate other Eavesdroppers and so does not get fixed


No pure strategy ESS unless V>C

Dove

Hawk

EDs


HAWK-DOVE – Johnstone 2001

Eavesdropping as a new strategy to play H-D games

  • Play Hawk when you observed your opponent losing

  • Play Dove when you observed opponent winning

  • Actually enhances the frequency of fighting – this is because the

    victory in one round increases the likelihood of winning again

    This “image” provides an additional benefit to winning

    favoring aggression

How does E’s change the level of fighting?

NO VICTORY SHOULD GO UNDISPLAYED


Fighting increases w/ E

and with V/C

Perfect info

H-D-E

Imperfect info

H-D-E

H-D


Victory displays and acoustics

in Tropical boubous


SOCIAL EAVESDROPPER

INFO

Clearly Social Eavesdropping

occurs by both sexes

INFO


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