Introduction to Psychology Suzy Scherf Lecture 13: How Do We Interact? Why be Social?

1. Introduction to Psychology Suzy Scherf Lecture 13: How Do We Interact? Why be Social? Why do Families Fight? Conflict Resolution

2. Why be Social? Why are some organisms social and others are not? Isn’t is always beneficial for a species to be social?

3. Why be Social? Isn’t is always beneficial for a species to be social? Not Necessarily! Have to weigh the costs and benefits of being social

4. Why be Social? What are the benefits of being social? 1. Can share knowledge about where resources are located 2. If you hang out in groups, you may have more protection from predators

5. Why be Social? What are the costs of being social? 1. Have to compete for resources 2. If you hang out in groups, you may be more visible to predators

6. Why be Social? Even the social nature of a species is likely to be an adaptation designed by natural selection. Selection favors social habits if the benefits associated with others outweigh the costs!

7. Why be Social? What are the environmental conditions that would encourage a species to be social?

8. Why be Social? For example, why are virtually all great apes social except the Orangutan?

9. Why be Social? For example, why are virtually all great apes social except the Orangutan? 1. Orangutans live up in trees of rain forests - predators a minimum 2. Orangutans are large-bodied - predators a minimum

10. Why be Unsocial? ** There is no anti-predator benefit for Orangutans to be social ** Orangutans eat from trees that fruit on different cycles and are hard to find - don’t want to share rare resources

11. Why be Social? Some general selection pressures favoring social habits: 1. Patch size - food distribution small, scattered = non-social large, shareable = social

12. Why be Social? Some general selection pressures favoring social habits: 2. Predators: hunting small, available prey = non-social hunting large, unavailable prey = social

13. Why be Social? Some general selection pressures favoring social habits: 3. Common Non-food Resource: • locations of safety from predators • grouping to deal with physical forces in the environment

14. Why be Social? Do gorillas and chimps get an anti-predator benefit and/or have benefit from sharing resource knowledge?

15. Why be Social? • Gorillas and chimps have few natural predators • Gorillas and chimps don’t forage in big groups - food is fairly available

16. Why be Social? Protection from each other is the biggest benefit of being social for chimps and gorillas • Males commit infanticide • Males fight for dominance and often kill each other

17. Why be Social? Protection from individuals within own species is also a selection pressure favoring social habits - even at the cost of other opposing pressures not to be social

18. Why be Social? What may have been some of the selection pressures favoring social habits in our ancestors?

19. Selection Pressures Favoring Social Habits in Our Ancestors 1. They inhabited more open, less forested country • More time on the ground = Increased vulnerability to predators • More time on the ground = More access to herds for food

20. Selection Pressures Favoring Social Habits in Our Ancestors 2. Having access to grazing herd • Dietary shift to dependence on meat • More meat dependence = more collaborative hunting

21. Selection Pressures Favoring Social Habits in Our Ancestors 3. Non-meat food scattered in rich patches • Sharing knowledge about rich patches of food or water benefits individuals within the group

22. Selection Pressures Favoring Social Habits in Our Ancestors 4. Protection from each other • Foraging alone vs in small groups

23. Social Life in the EEA Communities organized around kinship Small populations in which most of the individuals were related genetically

24. Social Life in the EEA Biological Kinship (even today) fundamentally influences social interactions WHY? Because we share genes!

25. Biological Kinship Direct vs. Indirect genetic routes to the next generation • Direct Route = Having own offspring • Indirect Route = Kin Selection

26. Biological Kinship You can pass your own genes down via reproduction but you can also encourage the reproduction fitness of those that you share genes with However, encouraging the reproductive fitness of someone else may cost you!

27. Kin Selection Kin Selection can only work if altruistic traits are selectively aimed at genetically relatives!

28. Kin Selection Altruistic traits = those that may cost you while benefiting someone else Kin Selection = altruistic genes can spread by benefiting other carriers of the same gene

29. Kin Selection Kin Selection can be described by a mathematical relationship: rb > c r = coefficient of genetic relatedness (0-1) b = benefit to the recipient c = cost to altruist

30. Kin Selection Example rb > c r = siblings (.50) b = .25 units of fitness (4 acts would increase the recipient’s reproductive success by 1 offspring) c = 0.1 units of fitness (10 acts would reduce the altruist’s reproducitve success by 1 offspring (.5)(.25) > (.1)

31. Kin Selection Example rb > c (.5)(.25) > (.1) This alturistic trait is likely to be selected for by natural selection. (.5)(.25) < (1) This alturistic trait is not likely to be selected for by natural selection.

32. Kin Selection Example: The White-Fronted Bee Eater • When resources scarce (i.e. food, mating opportunities, territory) older siblings will often stay in the nest after sexual maturity to help raise siblings • Sometimes, parents even recruit grown offspring as helpers by harassing them

33. But We do Help Folks We’re not Biologically Related to... Reciprocity - you-scratch-my-back-and-I’ll-scratch-yours

34. But We do Help Folks We’re not Biologically Related to... Reciprocity occurs consistently under some specific conditions…. 1. Cost of reciprocity have to be small compared to the benefits of reciprocity

35. But We do Help Folks We’re not Biologically Related to... Reciprocity occurs consistently under some specific conditions…. 2. The altruist and the recipient must regularly exchange roles

36. But We do Help Folks We’re not Biologically Related to... Reciprocity under these conditions turns short-term altruism into long-term cooperation!

37. But We do Help Folks We’re not Biologically Related to... Reciprocity can only be selected for if cheaters are discriminated against! Else the cheaters would always win and the altruists would always loose

38. But We do Help Folks We’re not Biologically Related to... Reciprocal Altruism can only spread if altruism is withheld from cheaters. How do we know who the cheaters are without getting burned all the time?

39. How do we Recognize Cheaters? 1. Recognition of individuals - especially those with whom we regularly interact 2. Tit-for-tat strategy!

40. Tit-for-Tat Strategy of Cheater Detection Prisoner’s Dilemma Your best friend and you have been accused of cheating on an exam. You guys know that you did actually cheat on the exam. You have to meet with the professor separately, but agree before hand to keep silent.

41. Tit-for-Tat Strategy of Cheater Detection Prisoner’s Dilemma Your professor has enough evidence to convince the dean that you were cheating to a lesser degree than you actually did.

42. Tit-for-Tat Strategy of Cheater Detection Prisoner’s Dilemma If you both remain silent, you will both get a Incomplete in the class. 2. If you both confess you will both get an F in the class.

43. Tit-for-Tat Strategy of Cheater Detection Prisoner’s Dilemma 3. If you or your friend remain silent while the other confesses, the one that confesses can finish the course but the other has to leave school.

44. Tit-for-Tat Strategy of Cheater Detection Your Friend’s Choice Silent Confess Your Choice You leave school and your friend finishes the course Both get I Silent Your friend leaves school and you finish the course Both get F Confess What would you do?

45. Tit-for-Tat Strategy of Cheater Detection What would you do if you went double-or-nothing? What would you do if your friend cheated the first time? What would you do if your friend keep silent the first time?

46. Tit-for-Tat Strategy of Cheater Detection People tend to use a tit-for-tat strategy: 1. Cooperate on first round 2. On the second round, do what your friend did of the first round

47. Tit-for-Tat Strategy of Cheater Detection People tend to use a tit-for-tat strategy: Tit-for-Tat fosters cooperation, but punishes cheaters!

48. Other Kinds of Social Interaction What does kin selection theory say about decision-making with respect to helping others?

49. Decision Making to Help People are much more likely to help biological relatives than to help unrelated individuals This is true especially in dire situations and varies with reproductive value!

50. 75 10 18 45 Decision Making to Help Highest Reproductive Value Tendency to Help < 1 yr. Age of Target