Module 1: Evolution and Module 1: Evolution and EconomicsEconomics

An Analysis of You:An Analysis of You:Prisoner’s DilemmaPrisoner’s Dilemma

Prisoner’s DilemmaPrisoner’s Dilemma This game is played by two This game is played by two

people, designated A and B. people, designated A and B. A plays first and can either A plays first and can either

cooperate or defect. cooperate or defect. Knowing A’s choice, B can Knowing A’s choice, B can

then either cooperate or then either cooperate or defect. defect.

A

C

D

BC D

A:$30B:$30

A:$10B:$45

A:$15B:$15

A:$45B:$10

Player A goes first without knowing what B will do.Player B goes second after learning A’s response.

Possible StrategiesPossible Strategies

Possible strategies of the sequential game

A B, if A plays C B, if A plays D StrategyC C C UNCONDITIONAL COOPERATORC C D OPTIMISTIC CONDITIONAL COOPERATORD C D PESSIMISTIC CONDITIONAL COOPERATORC D D OPTIMISTIC CONDITIONAL DEFECTORD D D UNCONDITIONAL DEFECTORC D C ?D C C ?D D C ?

Unconditional Cooperator: Unconditional Cooperator: CCCCCC

Friendly Tit-for-Tat: CCDFriendly Tit-for-Tat: CCD

Optimistic Non-Cooperator: CDDOptimistic Non-Cooperator: CDD

Pessimistic Tit-for-Tat: DCDPessimistic Tit-for-Tat: DCD

Unconditional Non-Cooperator: Unconditional Non-Cooperator: DDDDDD

Wingnuts:Wingnuts:CDC, DCC, DDCCDC, DCC, DDC

A DDC Player:“Player A will know I helped them and they might help me in the future.”

Your Population?Your Population?

1 23 T-4

T-4

A DCD Player:“I don’t think there are too many people in here who wouldn’t want $45 over $30 if we both decided to cooperate.”

TRUSTTRUST Cooperation by Player A demonstrates trust.Cooperation by Player A demonstrates trust.

A CDD Player:“If my partner sees that I chose to cooperate, they may choose to be altruistic and cooperate too so that we both get thirty dollars.”

RECIPROCITYRECIPROCITY Cooperating with a cooperative first mover Cooperating with a cooperative first mover

demonstrates reciprocity.demonstrates reciprocity. A CCD Player:“I would cooperate because that’s what I wanted somebody to do, and I’m a nice guy.”

A CDD Player:“Because I will make more money this way and the first player can’t stop me.”

Self-SacrificeSelf-Sacrifice Cooperating with a non-cooperative first Cooperating with a non-cooperative first

mover demonstrates self-sacrifice.mover demonstrates self-sacrifice.A CCC Player:“The effect on me is minimal, but it helps the other person immensely.”

The Scientific MethodThe Scientific Method Intro: Ask a question, make a hypothesis.Intro: Ask a question, make a hypothesis. Methods: Do an experiment.Methods: Do an experiment. Results: Analyze outcomesResults: Analyze outcomes

Topics for Today:GenderPunishment (&

Gender)One Idea From MeA Few From You

Statistical TestsStatistical Tests

Statistical TestsStatistical Tests Effect SizeEffect Size

The magnitude of the relationship between The magnitude of the relationship between variables.variables.

Specific to a particular test.Specific to a particular test. pp-value-value

The probability that an effect size is observed by The probability that an effect size is observed by chance.chance.

As the sample size increases, the As the sample size increases, the pp-value goes -value goes down.down.

Statistical TestsStatistical Tests t-testt-test::

A t-test determines whether the means of two A t-test determines whether the means of two separate groups are equal or not.separate groups are equal or not.

Do Males and Females Behave Do Males and Females Behave Differently in the Game?Differently in the Game?

Null HypothesisNull Hypothesis There is no relationship between gender and first There is no relationship between gender and first

mover behavior.mover behavior. Alternate HypothesisAlternate Hypothesis

One gender offers cooperation more often than the One gender offers cooperation more often than the other.other.

Trust Behavior Between GendersTrust Behavior Between Genders

Do Males and Females Behave Do Males and Females Behave Differently …Differently …

In trust behavior?

Male Offers = Female Offers?

Male Mean = .64Female Mean = .65Males = 58 Females = 57

p-value = .901.901 > .05

Insignificant!

Reciprocity Between GendersReciprocity Between Genders

Do Males and Females Behave Do Males and Females Behave Differently …Differently …

In reciprocity?

Male Reciprocity = Female Reciprocity?

Male Mean = .45Female Mean = .57Males = 58 Females = 57

p-value = .120.120 > .05

Insignificant!

Punishment:Punishment:Strategy DifferencesStrategy Differences

Without Punishment With Punishment

Using VariablesUsing Variables Independent VariableIndependent Variable

Something that is controlled for by the researcher.Something that is controlled for by the researcher. Dependent VariableDependent Variable

Something that is observed in terms of the Something that is observed in terms of the independent variables.independent variables.

Independent Variable:

Punishment

Dependent Variables:

TrustReciprocity

Altruism

What Punishment Does…What Punishment Does…TrustTrust

A CCC Player:“I would cooperate so I wouldn’t get punished.”

Played DDD in the first game.

What Punishment Does…What Punishment Does…TrustTrust

Offers of Cooperation:w/o Punishment = .64w/ Punishment = .90

p < .0001Significant!

What Punishment Does…What Punishment Does…ReciprocityReciprocity

Offers of Cooperation:w/o Punishment = .50w/ Punishment = .85

p < .0001Significant!

What Punishment Does…What Punishment Does…Self SacrificeSelf Sacrifice

A CCC Player:“Because if I don’t cooperate, A could punish me.”

Played CDD in the first game.

What Punishment Does…What Punishment Does…Self-SacrificeSelf-Sacrifice

Offers of Cooperation:w/o Punishment = .09w/ Punishment = .20

p < .012Significant!

How Do People Punish?How Do People Punish?

Punishment:Punishment:In-Class Study #2In-Class Study #2

Selfish Selfish PunishersPunishers

More MalesMore Males Invest More in Invest More in PunishmentPunishment

Moralistic Moralistic PunishersPunishers

More FemalesMore Females Invest Less in Invest Less in PunishmentPunishment

PunishmentPunishment

Cooperative/ Non-

Cooperative Behavior

Investment in

Punishment

Male/Female

Selfish vs. Moralistic Punishers:Selfish vs. Moralistic Punishers:SexSex

Moralistic Moralistic PunishersPunishers

Selfish Selfish PunishersPunishers

MalesMales 2424 1818

FemalesFemales 1818 2222

Null Hypothesis:Moralistic & Selfish Punishers are distributed equally between the sexes.

Alternate Hypothesis:They are not.

p = .272Do not reject null

hypothesis!

PunishmentPunishment

Cooperative/ Non-

Cooperative Behavior

Investment in

Punishment

Male/Female

Selfish vs. Moralistic PunishersSelfish vs. Moralistic PunishersInvestment in PunishmentInvestment in Punishment

Null Hypothesis:Moralistic & Selfish Punishers punish equally.

Alternate Hypothesis:They do not punish equally.

p = .683Do not reject null

hypothesis!

PunishmentPunishment

Cooperative/ Non-

Cooperative Behavior

Investment in

Punishment

Male/Female

Selfish vs. Moralistic PunishersSelfish vs. Moralistic PunishersInvestment in PunishmentInvestment in Punishment

Null Hypothesis:Males & Females punish equally.

Alternate Hypothesis:They do not punish equally.

p < .001Reject null hypothesis!

Males punish more!

PunishmentPunishment

Cooperative/ Non-

Cooperative Behavior

Investment in

Punishment

Male/Female

Social Dependency

Predictors of Cooperation:Predictors of Cooperation:In-Class Study #1In-Class Study #1

Risk Taking Behavior

Trusting PeopleSocial Integration

First Mover Behavior:First Mover Behavior:Based on Trust?Based on Trust?

Will People Reciprocate

?

First Mover Behavior

Risk Taking Behavior

p = .087

p = .378

Risk BehaviorRisk BehaviorQuestion For Sure Your

ColorOther Color

1 Win $2.00 Win $10.00

Win $2.00

2 Win $3.00 Win $10.00

Win $2.00

3 Win $4.00 Win $10.00

Win $2.00

4 Win $5.00 Win $10.00

Win $2.00

5 Win $6.00 Win $10.00

Win $2.00

6 Win $7.00 Win $10.00

Win $2.00

Score = 6Most Risky

Risk BehaviorRisk BehaviorQuestion For Sure Your

ColorOther Color

1 Win $2.00 Win $10.00

Win $2.00

2 Win $3.00 Win $10.00

Win $2.00

3 Win $4.00 Win $10.00

Win $2.00

4 Win $5.00 Win $10.00

Win $2.00

5 Win $6.00 Win $10.00

Win $2.00

6 Win $7.00 Win $10.00

Win $2.00

Score = 3Mildly Risky

Risk BehaviorRisk BehaviorQuestion For Sure Your

ColorOther Color

1 Win $2.00 Win $10.00

Win $2.00

2 Win $3.00 Win $10.00

Win $2.00

3 Win $4.00 Win $10.00

Win $2.00

4 Win $5.00 Win $10.00

Win $2.00

5 Win $6.00 Win $10.00

Win $2.00

6 Win $7.00 Win $10.00

Win $2.00

Score = 1Least Risky

Risk BehaviorRisk Behavior

Risk Behavior and Gender:Risk Behavior and Gender:Discussion Section 1Discussion Section 1

Null Hypothesis:Moralistic & Selfish Punishers punish equally.

Alternate Hypothesis:They do not punish equally.

p = .061Do not reject null

hypothesis!

Ambiguity BehaviorAmbiguity BehaviorQuestion For Sure Your

ColorOther Color

1 Win $2.00 Win $10.00

Win $2.00

2 Win $3.00 Win $10.00

Win $2.00

3 Win $4.00 Win $10.00

Win $2.00

4 Win $5.00 Win $10.00

Win $2.00

5 Win $6.00 Win $10.00

Win $2.00

6 Win $7.00 Win $10.00

Win $2.00

Are people…

Pessimistic

Or Optimistic?

Ambiguity BehaviorAmbiguity Behavior

Ambiguity Behavior, Trust and Ambiguity Behavior, Trust and Upbringing?Upbringing?

Discussion Section 6Discussion Section 6Trust

Behavior?Reaction to Ambiguity

Rural/Urban

p = .901

p = .112

Delayed PayoffsDelayed PayoffsQuestion Next Week One Day

Later1 $35.00 $40.00

2 $30.00 $40.00

3 $25.00 $40.00

4 $20.00 $40.00

5 $15.00 $40.00

6 $10.00 $40.00

7 $5.00 $40.00

Score = 0Most Patient

Delayed PayoffsDelayed PayoffsQuestion Next Week One Day

Later1 $35.00 $40.00

2 $30.00 $40.00

3 $25.00 $40.00

4 $20.00 $40.00

5 $15.00 $40.00

6 $10.00 $40.00

7 $5.00 $40.00

Score = 4Mildly Patient

Delayed PayoffsDelayed PayoffsQuestion Next Week One Day

Later1 $35.00 $40.00

2 $30.00 $40.00

3 $25.00 $40.00

4 $20.00 $40.00

5 $15.00 $40.00

6 $10.00 $40.00

7 $5.00 $40.00

Score = 7Least Patient

Delayed PayoffsDelayed Payoffs

Delayed Payoffs and Urban/Rural:Delayed Payoffs and Urban/Rural:Discussion Section 3Discussion Section 3

Null Hypothesis:Desire for immediate pay is unrelated to urban/rural upbringing.

Alternate Hypothesis:People from different upbringings fel differently about delayed payoffs.

p = .159Do not reject null

hypothesis!

A Biological PerspectiveA Biological Perspective

A Biological PerspectiveA Biological Perspective

Dopamine Dopamine SystemSystem

Bilateral InsulaBilateral Insula

Brain CenterBrain Center

Reward circuitryReward circuitry

Disgust, Pain, Disgust, Pain, HungerHunger

JobJob

During mutual During mutual cooperationcooperation

During low During low offers in U.G.offers in U.G.

Stimulated Stimulated during during

Games?Games?

Strength correlates Strength correlates with cooperation with cooperation and punishment.and punishment.

Increases Increases PunishmentPunishment

Operation Operation during Games?during Games?

An Evolutionary PerspectiveAn Evolutionary Perspective

Need for Cooperation in Evolutionary

Past

Neurology which

Supports Cooperation

Cooperative Behavior

“Does my Environment

Need Cooperation?”