Download - Trust and deceit in the animal kingdom Liesbeth Sterck Animal Ecology, UU Ethology Research, BPRC
Trust and deceit in the animal kingdom
Liesbeth Sterck
Animal Ecology, UUEthology Research, BPRC
Trust
Nature in tooth and claw
• Monkey business• Sly as a fox
Cooperation in theory
• Evolution on level individual
• Altruism: benefit for
other, costs for individual
• Problem with cheaters
Cooperation in theory
• Mutualism: simultaneous exchange of benefits
• Altruism: donor incurs cost; recipient benefits– Kin selection– Reciprocal altruism
Kin selection (Hamilton 1964)
• Altruism when:
• C < r*B
• Costs < relatedness * Benefits
• C < r*B r=1/2
r=1/4
r=1/8
Kin selection (Hamilton 1964)
Kin selection (Hamilton 1964)
• C < r*B
Animals can be nice to kin
http://www.youtube.com/watch?v=o2B1AJ3ZaUA
Cooperation with non-kin?
Reciprocal altruism (Trivers 1971)
• ‘If you scratch my back, I’ll scratch yours’• Non-kin• Not simultaneous
Prisoners Dilemma
• Cooperate or cheat (defect)
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
Humans• Humans are a group-living species
– Family / kin– Friends / acquaintances / colleagues
-- Warfare
Groups are diverse
• Size– From 2 - 100 - 10.000s individuals
• Composition– Changing- fixed
• Recognition group members– Anonymous –categories – individuals
• Reproduction– One female (+ male) - everyone
Cooperation in practice 1
• Why do primates live in groups?
Group living: advantages
• Warning against predators (van Schaik 1989)
Group living: disadvantages
• Competition (Wrangham 1980; Sterck et al. 1997}
Males:– Matings
Females:– Food
Group living: advantages
• Infanticide avoidance (Sugiyama 1965; 1966; Hrdy 1977; Sterck et al. 1997)
Balance in costs and benefits
Protection against predators and infanticide
Competition
Primate peculiarity:groups containboth females and males
Cooperation in practice 2
• How do primates live in groups?
How primates live in groups
• How complex is living in a primate group
• Do they take benefit others into account
Methods
• From individual to group:
• Observations• Behavioural experiments
Methods
• From individual to group:
• Observations• Behavioural experiments
• Computer simulations
How primates live in groups
• How complex is living in a primate group– Dominance– Good relationships
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)
Good relationships
Advantages
Advantages male – female relationships
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
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
Friendship• Do they know their friends?
Computer simulation of behaviour (Hemelrijk 1998, 2000; Evers, Sterck et al. 2011, 2012, 2014)
Computer simulation of behaviour (Evers, Sterck et al. MS)
Grooming= friendship
Dominance
Dom
inan
ce
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
Primate group living
• Compete and cooperate in group• Relationships
– Kinship– Dominance– Friendship = ‘trust’
• Friendships take time to build and last long
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
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
• 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
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
Inequity Aversion
38
• Negative inequity aversion– React to getting less than other
• Positive inequity aversion– React to getting more than other
Inequity Aversion (Brosnan & de Waal 2003)http://www.youtube.com/watch?v=-KSryJXDpZo
capuchin monkey refuses food
39
Inequity Aversion (IA): critisism
40
• Newer data: no IA
The task for macaques
41
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
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
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
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
Nature in tooth and claw?
• Monkey business• Sly as a fox
Care and friendship
• C < r*B
Conclusion
• Deceit kept in limits: otherwise no cooperation• Competition and cooperation in group
– Dominance and friendship
• Trust and friendship crucial for cooperation
Thank you
Humans are smart and have large brains
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
Social intelligence
• Evidence in favour:• Group size and brain size are correlated in
primates, cetaceans and carnivores (Dunbar 1998)