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Trust and deceit in the animal kingdom

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

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Trust and deceit in the animal kingdom

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  1. Trust and deceit in the animal kingdom Liesbeth Sterck Animal Ecology, UU Ethology Research, BPRC

  2. Trust

  3. Nature in tooth and claw • Monkey business • Sly as a fox

  4. Cooperation in theory • Evolution on level individual • Altruism: benefit for other, costs for individual • Problem with cheaters

  5. Cooperation in theory • Mutualism: simultaneous exchange of benefits • Altruism: donor incurs cost; recipient benefits • Kin selection • Reciprocal altruism

  6. Kin selection (Hamilton 1964) • Altruism when: • C < r*B • Costs < relatedness * Benefits

  7. Kin selection (Hamilton 1964) • C <r*B r=1/2 r=1/4 r=1/8

  8. Kin selection (Hamilton 1964) • C <r*B

  9. Animals can be nice to kin Cooperation with non-kin? http://www.youtube.com/watch?v=o2B1AJ3ZaUA

  10. Reciprocal altruism (Trivers 1971) • ‘If you scratch my back, I’ll scratch yours’ • Non-kin • Not simultaneous

  11. Prisoners Dilemma • Cooperate or cheat (defect)

  12. 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

  13. Humans • Humans are a group-living species • Family / kin • Friends / acquaintances / colleagues -- Warfare

  14. Groups are diverse • Size • From 2 - 100 - 10.000s individuals • Composition • Changing- fixed • Recognition group members • Anonymous –categories – individuals • Reproduction • One female (+ male) - everyone

  15. Cooperation in practice 1 • Why do primates live in groups?

  16. Group living: advantages • Warning against predators (van Schaik 1989)

  17. Group living: disadvantages Males: • Matings • Competition (Wrangham 1980; Sterck et al. 1997} Females: • Food

  18. Group living: advantages • Infanticide avoidance (Sugiyama 1965; 1966; Hrdy1977; Sterck et al. 1997)

  19. Balance in costs and benefits Protection against predators and infanticide Competition Primate peculiarity: groups contain both females and males

  20. Cooperation in practice 2 • How do primates live in groups?

  21. How primates live in groups • How complex is living in a primate group • Do they take benefit others into account

  22. Methods • From individual to group: • Observations • Behavioural experiments

  23. Methods • From individual to group: • Observations • Behavioural experiments • Computer simulations

  24. How primates live in groups • How complex is living in a primate group • Dominance • Good relationships

  25. Bob (29) Relationships in group (Massen, Sterck &de Vos 2010) Timon (20) Sitting together 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 Kin Dominance Friendship 29 20

  26. Good relationships Advantages male – female relationships Advantages

  27. Friendship and mating success (Massen, Sterck et al. 2012) * Mating No mating Grooming by males (sec/hour) Mating season

  28. Friendship and paternity(Massen, Sterck et al. 2012) * Proximity of male (rank) other male father males

  29. Friendship • Do they know their friends?

  30. Computer simulation of behaviour(Hemelrijk 1998, 2000; Evers, Sterck et al. 2011, 2012, 2014)

  31. Computer simulation of behaviour(Evers, Sterck et al. MS) Grooming= friendship Dominance Dominance

  32. Computer simulation of behaviour(Evers, Sterck et al. MS) Grooming = friendship Dominance Dominance

  33. Primate group living • Compete and cooperate in group • Relationships • Kinship • Dominance • Friendship = ‘trust’ • Friendships take time to build and last long

  34. 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

  35. Cooperation: pro-social behaviour • Do primates bestow other a favor? (Massen, vd Berg, Spruijt en Sterck 2010: PlosOne 5(3): e9734)

  36. Cooperation: pro-social behaviour • To kin • To high-ranking animals Bestow (Massen, vd Berg, Spruijt en Sterck 2010: PlosOne 5(3): e9734) Neutral Withhold High rank Low rank

  37. 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)

  38. Inequity Aversion • Negative inequity aversion • React to getting less than other • Positive inequity aversion • React to getting more than other

  39. Inequity Aversion (Brosnan & de Waal 2003) http://www.youtube.com/watch?v=-KSryJXDpZo capuchin monkey refuses food

  40. Inequity Aversion (IA): critisism • Newer data: no IA

  41. The task for macaques

  42. The Conditions O,5 kg O,5 kg 2,3 kg 2,3 kg No effort (provisioning) Equity No effort (provisioning) Inequity Small effort Equity Small effort Inequity Large effort Equity Large effort Inequity Large effort Reward & effort inequity

  43. Proportion of acceptance/performanceof all equity conditions for all animals Significant drop in performance (for low value reward) with increasing workload 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

  44. Proportion of acceptance/performanceof dominant subjects Disadvantageous Inequity aversion in small effort test 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

  45. 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 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

  46. Nature in tooth and claw? • Monkey business • Sly as a fox

  47. Care and friendship • C <r*B

  48. Conclusion • Deceit kept in limits: otherwise no cooperation • Competition and cooperation in group • Dominance and friendship • Trust and friendship crucial for cooperation

  49. Thank you

  50. Humans are smart and have large brains

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