1. Cooperation within Groups
Affiliation as a fundamental human motive.
- “Sociometer theory” of self-esteem.
- The reconnection hypothesis.
Reciprocity and the cheater problem.
- Psychological solutions to the cheater problem.
- Memory. 
- Logical reasoning.

2. Dawkins, Chapter 10
Benefits of being in a group.
Evolution of “cooperation” between species.
Evolution of cooperation within a species.
Reciprocal altruism.
Buss, Chapter 9 (“Cooperative Alliances”):
Evolution of cooperation, friendship, etc.
The problem of “cheaters”
Psychological adaptations that solve the cheater problem.

3. Background: Humans are social animals
Wikipedia says:
“Social animals are creatures that are greatly interactive with other members of its species, with an individual animal's success highly dependent on the overall cohesion and propagation of the group.”

4. !
(Kenrick et al., 2010)

5. If there is are specific motivational mechanisms that evolved to facilitate social affiliation, then…
- Perceived threats to social affiliation are likely to arouse a functionally specific affective response.
- Perceived threats to social affiliation are likely to lead to functionally useful cognitive and behavioral responses.

6. “Sociometer theory” of self-esteem
- Fitness benefits associated with being a member of a social group.
- Fundamental human motive associated with affiliation.
- Evolved emotional signal indicating whether that need is being met or not.
- The specific signal: Temporary feelings about self (“state self-esteem”).
- Key prediction: State self-esteem varies in response to information about social inclusion and (especially) social exclusion.

7. Experimental test of this hypothesis.
(Leary et al., 1995)
Manipulated: Social inclusion or social exclusion
Random draw or other’s choice
Measured: State self esteem

8. Results: State self-esteem:
(Leary et al., 1995)

9. The reconnection hypothesis.
More favorable responses to other people
(in order to forge new social connections with them)
Social exclusion
Need for reconnection

10. Research results:
More positive impressions of potential interaction partners
More prosocial behavior when interacting with new people
Social exclusion
Need for reconnection
But:
- Only toward new people (not toward actual rejecters).
- Only if actual potential for interaction (not if no functional benefit).
- Only if social optimistic (not if socially anxious).
(Maner et al., 2007)

11. Reciprocity and the cheater problem:
Living in groups was associated with fitness benefits.
A lot of these benefits accrued from cooperative behavior within groups.
Cooperative behavior involved a kind of “social contract”
(reciprocity and fairness in social exchanges).
This introduced the potential for “cheating.”
Presence of “cheaters” imposed fitness costs on others.
So: Adaptations to deal with this problem.

12. Cultural solutions to the cheater problem:
- Norms that encourage reciprocity.
- Norms that endorse punishment of cheaters.
- Norms that reward people who punish cheaters.
- Beliefs about supernatural beings that watch for—and punish—cheating.

13. Psychological solutions to the cheater problem:
- Memory for the faces of “cheaters”.
- Logical reasoning in the domain of “social contracts.”

14. Memory for the faces of “cheaters”:
(Buchner, Bell, Mehl, & Musch, 2009)
Exposure to faces and descriptions
Later measures of recognition memory and source memory
“Neutral”
“Cooperator”
“Cheater”

15. Source memory for faces:
(Under conditions in which people correctly judge a face as familiar, what is the likelihood that they also remember why that face is familiar?)
(Buchner et al., 2009)

16. Logical reasoning in the domain of “social contracts”:
Basic idea: Evolved cognitive mechanisms for reasoning about social contracts (which helps to efficiently detect cheaters).
Implication:
- Although people are typically pretty bad at understanding the formal logic of conditional rules (“If X, then Y”)…
- People are typically very good at understanding the formal logic of conditional rules within the specific context of social contracts (that might potentially be exploited by cheaters.)
John Tooby & Leda Cosmides

17. Task testing understanding of formal logic of conditional rules:
Context: The transportation that people use when going places.
Rule: “If a person goes to work, that person must take the bus.”
Task: Four cards: "Each card represents one person. One side of a card tells where a person went, and the other side of the card tells how that person got there. Indicate only those card(s) you definitely need to turn over to see if this rule has been violated."
Work
Movie
Bus
Taxi 1 2 3 4

18. A logically identical task, in the domain of social contracts:
Context: Exchange of goods at a watch store where watches costs $50.
Rule: “If a customer gives a shopkeeper $50, the shopkeeper must give the customer a watch.”
Task: Four cards: "Each card represents one person. One side of a card tells how much money a customer gave to the shopkeeper, and the other side of the card tells what the shopkeeper gave to the customer. Indicate only those card(s) you definitely need to turn over to see if this rule has been violated."
$50
$20
Watch
No watch 1 2 3 4

19. Results from lots of studies:
- Although people are typically pretty bad at understanding the formal logic of conditional rules (“If X, then Y”)…
- People are typically very good at understanding the formal logic of conditional rules within the specific context of social contracts (that might potentially be exploited by cheaters.)
Social contracts are most likely to be exploited by cheaters if…
- Cheating provides actual benefits to cheaters.
- There are people who actually intend to cheat.
- Cheating is actually easy to do.

20. Logically correct responses on conditional reasoning tasks:
Might cheater benefit?
YES No
Does cheater have intention?
Is it easy to cheat?
(Cosmides, Barrett, & Tooby, 2010)

21. Results from lots of studies:
- Although people are typically pretty bad at understanding the formal logic of conditional rules (“If X, then Y”)…
- People are typically very good at understanding the formal logic of conditional rules within the specific context of social contracts (that might potentially be exploited by cheaters.)
Additional results:
- Culturally “universal”.
- Functionally distinct neural circuitry.

22. The bottom line…
There appear to be specialized psychological adaptations that allow people to think logically about social contracts (and therefore to respond adaptively to people who violate those contracts).
Specific features of human cognition evolved in response to the specific fitness problems associated with reciprocity and cooperation within groups.