trust and deceit in the animal kingdom
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Trust and deceit in the animal kingdom. Liesbeth Sterck Animal Ecology, UU Ethology Research, BPRC. Trust. Nature in tooth and claw. Monkey business Sly as a fox. Cooperation in theory. Evolution on level individual - PowerPoint PPT PresentationTRANSCRIPT
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Trust and deceit in the animal kingdom
Liesbeth Sterck
Animal Ecology, UUEthology Research, BPRC
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Trust
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Nature in tooth and claw
• Monkey business• Sly as a fox
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Cooperation in theory
• Evolution on level individual
• Altruism: benefit for
other, costs for individual
• Problem with cheaters
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Cooperation in theory
• Mutualism: simultaneous exchange of benefits
• Altruism: donor incurs cost; recipient benefits– Kin selection– Reciprocal altruism
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Kin selection (Hamilton 1964)
• Altruism when:
• C < r*B
• Costs < relatedness * Benefits
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• C < r*B r=1/2
r=1/4
r=1/8
Kin selection (Hamilton 1964)
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Kin selection (Hamilton 1964)
• C < r*B
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Animals can be nice to kin
http://www.youtube.com/watch?v=o2B1AJ3ZaUA
Cooperation with non-kin?
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Reciprocal altruism (Trivers 1971)
• ‘If you scratch my back, I’ll scratch yours’• Non-kin• Not simultaneous
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Prisoners Dilemma
• Cooperate or cheat (defect)
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Reciprocal altruism (Trivers 1971)
• ‘If you scratch my back, I’ll scratch yours’• Non-kin• Not simultaneous• Repeated encounters• Individual recognition,
e.g. in a group
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Humans• Humans are a group-living species
– Family / kin– Friends / acquaintances / colleagues
-- Warfare
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Groups are diverse
• Size– From 2 - 100 - 10.000s individuals
• Composition– Changing- fixed
• Recognition group members– Anonymous –categories – individuals
• Reproduction– One female (+ male) - everyone
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Cooperation in practice 1
• Why do primates live in groups?
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Group living: advantages
• Warning against predators (van Schaik 1989)
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Group living: disadvantages
• Competition (Wrangham 1980; Sterck et al. 1997}
Males:– Matings
Females:– Food
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Group living: advantages
• Infanticide avoidance (Sugiyama 1965; 1966; Hrdy 1977; Sterck et al. 1997)
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Balance in costs and benefits
Protection against predators and infanticide
Competition
Primate peculiarity:groups containboth females and males
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Cooperation in practice 2
• How do primates live in groups?
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How primates live in groups
• How complex is living in a primate group
• Do they take benefit others into account
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Methods
• From individual to group:
• Observations• Behavioural experiments
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Methods
• From individual to group:
• Observations• Behavioural experiments
• Computer simulations
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How primates live in groups
• How complex is living in a primate group– Dominance– Good relationships
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Relationships in group(Massen, Sterck & de Vos 2010)
KinDominanceFriendship
niet verwant0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
familie0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 30 31 32 33 34 35
Sitti
ng to
geth
er
2920 Timon (20)
Bob (29)
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Good relationships
Advantages
Advantages male – female relationships
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Friendship and mating success (Massen, Sterck et al. 2012)
Gro
omin
g by
mal
es (s
ec/h
our)
Mating season
*
2006/07 2007/080
10
20
30
40
50
60
70
80
90
wel parenniet paren
Mating
No mating
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Friendship and paternity(Massen, Sterck et al. 2012)
alle vader0
1
2
3
4
5
6Pr
oxim
ity o
f mal
e (r
ank)
males
*
other malefather
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Friendship• Do they know their friends?
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Computer simulation of behaviour (Hemelrijk 1998, 2000; Evers, Sterck et al. 2011, 2012, 2014)
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Computer simulation of behaviour (Evers, Sterck et al. MS)
Grooming= friendship
Dominance
Dom
inan
ce
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Computer simulation of behaviour (Evers, Sterck et al. MS)
Grooming = friendship
Dominance
Dom
inan
ce
niet verwant0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
familie0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
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Primate group living
• Compete and cooperate in group• Relationships
– Kinship– Dominance– Friendship = ‘trust’
• Friendships take time to build and last long
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Primate cooperation in practice 2
• Do they take benefit others into account?
– Other-regarding preferences– Inequity aversion
• Yerkes 1930’s: http://www.youtube.com/watch?v=zrv91Pa3jgs
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Cooperation: pro-social behaviour• Do primates bestow other a favor?
(Masse
n, vd
Be
rg, S
pru
ijt en
Ste
rck 2
010
: Plo
sOn
e 5
(3): e97
34
)
35
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• To kin• To high-ranking animals
(Masse
n, vd
Be
rg, S
pru
ijt en
Ste
rck 2
010
: Plo
sOn
e 5
(3): e97
34
)
Bestow
Withhold
Neutral
High rank Low rank 36
Cooperation: pro-social behaviour
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Inequity Aversion
"Inequity exists for a person whenever his perceived job inputs and/or outcomes stand
psychologically in an obverse relation to what he perceives are the inputs and/or outcomes of
another" (Festinger 1957)
37
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Inequity Aversion
38
• Negative inequity aversion– React to getting less than other
• Positive inequity aversion– React to getting more than other
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Inequity Aversion (Brosnan & de Waal 2003)http://www.youtube.com/watch?v=-KSryJXDpZo
capuchin monkey refuses food
39
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Inequity Aversion (IA): critisism
40
• Newer data: no IA
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The task for macaques
41
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O,5 kg O,5 kg2,3 kg2,3 kg
1. No effort (provisioning) Equity
2. No effort (provisioning) Inequity
3. Small effort Equity
4. Small effort Inequity
5. Large effort Equity
6. Large effort Inequity
7. Large effort Reward & effort inequity
The Conditions
42
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Friedman test: n = 19, 2 = 15.84, df = 2, p = 0.001
Post-hoc Wilcoxon signed ranks tests:
Provisioning vs. 0,5 kg: n = 19, T+=62.5, pexact= 0.115Provisioning vs. 2,3 kg: n = 19, T+= 152, pexact< 0.0010,5kg vs. 2,3 kg: n = 19, T+= 117.5, pexact= 0.008
Proportion of acceptance/performanceof all equity conditions for all animals
Significant drop in performance (for low value reward) with increasing workload
43
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Wilcoxon signed ranks tests:
Provisioning: n = 12, T+= 21, pexact= 0.719Small Effort: n = 12, T+= 34, pexact= 0.023Large Effort (reward): n = 12, T+= 8.5, pexact= 0.211Large Effort (reward & effort): n = 12, T+= 15.5, pexact= 0.250
Proportion of acceptance/performanceof dominant subjects
Disadvantageous Inequity aversion in small effort test
44
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Wilcoxon signed ranks tests:
Provisioning: n = 9, T+= 3, pexact= 0.156Small Effort: n = 9, T+= 4, pexact= 0.219Large Effort (reward): n = 9, T+= 0, pexact= 0.008Large Effort (reward & effort): n = 9, T+= 4, pexact= 0.055
AIA: Proportion of acceptance/performance of subordinate partners
Performance for low value reward decreases when workload increases
At high workload, performance for high value reward significantly better then for low value reward --> no advantageous inequity aversion
45
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Nature in tooth and claw?
• Monkey business• Sly as a fox
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Care and friendship
• C < r*B
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Conclusion
• Deceit kept in limits: otherwise no cooperation• Competition and cooperation in group
– Dominance and friendship
• Trust and friendship crucial for cooperation
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Thank you
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Humans are smart and have large brains
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Social Intelligence Hypothesis• Primates have relatively large brains• Both cooperation and competition in group• Several hypotheses
– Primates ‘smart’ through social complexity
• Socially complex = socially intelligent
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Social intelligence
• Evidence in favour:• Group size and brain size are correlated in
primates, cetaceans and carnivores (Dunbar 1998)