1. Reciprocity and Cooperation
Benefits of living within cooperative groups.
Affiliation.
Psychological consequences of social exclusion.
(Social pain and re-connection.)
Reciprocity.
Evolution of reciprocal altruism.
The cheater problem, and psychological solutions.
(Implications for memory and logical reasoning.)

2. Benefits of living within cooperative groups.
Individual fitness depended substantially on being in a social group.
Individual fitness depended substantially on group-level outcomes, which benefited from cooperation within a group.
Psychological mechanisms
promoting affiliation
Psychological mechanisms
promoting reciprocity

3. Affiliation. “Need to belong” as a fundamental human motive.
(Specific psychological mechanisms evolved to regulate affiliative behaviors.)
Such as: Psychological responses to the experience of social exclusion.

4. Psychological responses to social exclusion.
Affective response: Social pain.
Cognitive and behavioral responses: Social re-connection.

5. Social Pain. A really long time age: Selection pressure: Fitness costs
associated with serious physical injury.
Evolution of pain mechanisms
(triggered by somatosensory stimuli).
Cognitive and behavioral responses
that averted serious physical injuries.
Much more recently:
Selection pressure: Fitness costs
associated with social exclusion.
Evolved re-purposing of pain mechanisms
(triggered by social stimuli).
Cognitive and behavioral responses
that facilitate social re-connection.

6. Social Pain. Some implications:
Overlap in brain regions associated with affective experience of physical pain and social pain.
People who are more sensitive to physical pain are also more sensitive to social pain.
Things that affect feelings of physical pain also affect feelings of social pain.
Reduced impact of ostracism on brain areas associated with social pain
Experimental Manipulation:
Tylenol vs. placebo
Lower levels of self-reported hurt feelings in social situations.
(DeWall et al., 2010)

7. Motivation to form social bonds with new sources of affiliation
Social re-connection.
Cognitive processes and behavioral inclinations that increase chances of forming new social bonds
Motivation to form social bonds with new sources of affiliation
Social exclusion
Research results: Social exclusion leads to…
Faster detection of smiling faces in a crowd of other faces.
Increased accuracy in discriminating between real smiles and fake smiles.
More positive impressions of other people, and more prosocial behavior when interacting with them. (But only if one there appears to be real potential for affiliation.)

8. Evolution of reciprocal altruism.
Analogous to kin selection…
Kin selection (“Hamilton’s rule”).
Genes promoting kin-directed
altruism will spread if r × b > c.
Reciprocal altruism:
Genes promoting reciprocal
altruism will spread if w × b > c.

9. Simple psychology of reciprocal altruism.
Inclination to be helpful toward others,
Especially if anticipate future interactions.
Obligation to be helpful toward others
who have been helpful to you in the past.
“social contract”

10. Simple psychology of reciprocal altruism.
Inclination to be helpful toward others,
Especially if anticipate future interactions.
Obligation to be helpful toward others
who have been helpful to you in the past.
But… The “cheater” problem.
Non-reciprocators (“cheaters”) may exploit others’ altruistic inclinations.
Additional adaptations to solve the cheater problem.

11. Cultural solutions to the cheater problem:
Cultural norms that encourage reciprocity.
Cultural norms that endorse punishment of cheaters.
Cultural beliefs about supernatural beings that
watch for—and punish—cheating.

12. Cognitive solutions to the cheater problem:
Altruistic inclinations calibrated to potential for reciprocal benefits.
For instance, more likely to help if:
- Anticipate longer relationship with other person.
- Other person has greater ability to reciprocate.
- Other person seems more willing to reciprocate.
These considerations matter especially when helping is more costly.
Memory for “cheaters.”
Logical reasoning in the domain of “social contracts.”

13. Memory for “cheaters.” Exposure to faces and descriptions.
(Buchner, Bell, Mehl, & Musch, 2009)
Exposure to faces and descriptions.
Measures of:
Recognition memory. (Likelihood that correctly recognize a face.)
Source memory. (If correctly recognize face, likelihood that also correctly remember why that face is familiar).
“Neutral”
“Cooperator”
“Cheater”

14. Memory for “cheaters.” Exposure to faces and descriptions.
(Buchner, Bell, Mehl, & Musch, 2009)
Exposure to faces and descriptions.
Measures of:
Recognition memory. (Likelihood that correctly recognize a face.)
Source memory. (If correctly recognize face, likelihood that also correctly remember why that face is familiar).
Results on measure of source memory:

15. Logical reasoning in the domain of “social contracts.”
Basic idea: To help solve the cheater problem, there evolved functionally-specialized cognitive mechanisms for reasoning about social contracts.
Implication:
Although people are typically pretty bad at intuitively understanding the formal logic of conditional rules (“If X, then Y”), people are typically very good at understanding this kind of logic within the specific context of social contracts (that might potentially be exploited by cheaters).
John Tooby & Leda Cosmides

16. [Example of typical task testing understanding of
formal logic of conditional rules]
Rule: “If a person goes to work, then 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 on this card."
Work
Movie
Bus
Taxi 1 2 3 4

17. [Example of a logically identical task,
specific to the domain of social contracts]
Rule: “If a customer gives a shopkeeper $50, then 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 on this card."
$50
$20
Watch
No watch 1 2 3 4

18. Logical reasoning in the domain of “social contracts.”
Results from lots of studies:
People are typically very good at understanding the formal logic of conditional rules within the specific context of social contracts.
Additional results:
Especially when the potential for cheating is especially high.
(E.g., cheating is easy to do, strong economic incentive to cheat, etc.)
Culturally “universal.”
Distinct neural mechanisms.