Cognitive Systems for Revenge
and Forgiveness
Michael McCullough
Department of Psychology
Evolution and Human Behavior Laboratory
University of Miami
Coral Gables, FL
Exploitation: A Fact of Life
Deterrence: Adaptations to Exploitation
Revenge as Deterrence
“Punishing strategies are
used to establish and
maintain dominance
relationships, to
discourage parasites and
cheats…and to maintain
cooperative behavior.”
Explaining Behavior:
Tinbergen’s (1963) Four Questions
1. Function: The Role that the
Behavior Plays in the Organism’s
Adaptation to Its Environment
2. Ontogeny: How the behavior
arises during the process of
development
3. Phylogeny: How continuous with
and different from other
species—including extinct
species from which it might have
descended?
4. Causation: Neural, hormonal,
physiological (& computational)
mechanisms that give rise to the
behavior
Our Experimental Model: The 3rd-Party
Punishment Game (3PPG)
Gives 0 - 50
Dictator: 100
Recipient: 0
Can pay to punish
Third Party: 50
Third-Party Punishment Game:
A First Look
Fehr & Fischbacher (2004)
Experiments 1 and 2
Do People Really Punish Altruistically? A
Closer Look
Pedersen, Kurzban, & McCullough (2013), Proceedings B
Modified Third-Party Punishment
Game: Round 1
Took $0
Recipient
Dictator
$5
$5
Fair Conditions
3rd Party
$5
Pedersen, Kurzban, & McCullough (2013) Proceedings B
Modified Third-Party Punishment
Game: Round 1
Took $4
Recipient
Dictator
$5
$5
Unfair Conditions
3rd Party
$5
Pedersen, Kurzban, & McCullough (2013) Proceedings B
Modified Third-Party Punishment
Game: Round 1
Took $4
Recipient
Dictator
$9
$1
Unfair Conditions
3rd Party
$5
Pedersen, Kurzban, & McCullough (2013) Proceedings B
Modified Third-Party Punishment
Game: Round 2
One decision: Can punish/reward
up to $5, or do nothing
Dictator
$5
Punishing costs ¼ removed,
money burned
Recipient
$5
R1 Dictator
Subject
“Doing another task”
3rd Party
$5
R1 Recipient
Pedersen, Kurzban, & McCullough (2013) Proceedings B
Design Recap
R1Dictator Decision
R1 Subject Role
Recipient
(fair)
3rd Party
(fair)
Recipient
(unfair)
3rd Party
(unfair)
Pedersen, Kurzban, & McCullough (2013) Proceedings B
Results: Punishment
Proportion
1
3rd Party (unfair)
n = 65
Recipient (unfair)
n = 61
1
0,9
0,9
0,8
0,8
0,7
0,7
0,6
0,6
0,5
0,5
0,4
0,4
0,3
0,3
0,2
0,2
0,1
0,1
0
0
-5 -4 -3 -2 -1
Punishment
0
1
2
3
Reward
4
5
-5
-4
-3
-2
-1
Punishment
0
1
2
3
4
5
Reward
Amount punished or rewarded ($)
Pedersen, Kurzban, & McCullough (2013) Proceedings B
Results: Punishment
1
0,9
Proportion
0,8
3rd Party (unfair)
n = 65
Recipient (unfair)
n = 61
1
0,9
p = .14
0,8
0,7
0,7
0,6
0,6
0,5
0,5
0,4
0,4
0,3
0,3
0,2
0,2
0,1
0,1
0
0
-5 -4 -3 -2 -1
Punishment
0
1
2
3
Reward
4
5
-5
-4
-3
-2
-1
Punishment
0
1
2
3
4
5
Reward
Amount punished or rewarded ($)
Pedersen, Kurzban, & McCullough (2013) Proceedings B
Results: Punishment
3rd Party (unfair)
n = 65
1
0,9
Proportion
1
0,9
p = .14
0,8
p < .001
0,8
0,7
0,7
0,6
0,6
0,5
0,5
0,4
0,4
0,3 p = .20
0,3
0,2
0,2
0,1
Recipient (unfair)
n = 61
2
p < .001
13
0,1
0
0
-5 -4 -3 -2 -1
Punishment
0
1
2
3
Reward
4
5
-5
-4
-3
-2
-1
Punishment
0
1
2
3
4
5
Reward
Amount punished or rewarded ($)
Pedersen, Kurzban, & McCullough (2013) Proceedings B
Results: Anger (controlling envy)
Anger (scale: 0-5)
Total N = 270
1,6
Fair
1,4
Unfair
1,2
1
0,8
0,6
0,4
0,2
0
Witness
3rd Party
Recipient
Error bars = +/- 1 SE
Pedersen, Kurzban, & McCullough (2013) Proceedings B
Results: Anger (controlling envy)
Anger (scale: 0-5)
Total N = 270
1,6
Fair
1,4
Unfair
1,2
1
0,8
0,6
0,4
0,2
0
Witness
3rd Party
Recipient
Error bars = +/- 1 SE
Pedersen, Kurzban, & McCullough (2013) Proceedings B
Results: Anger (controlling envy)
Anger (scale: 0-5)
Total N = 270
1,6
Fair
1,4
Unfair
***
d = .77
1,2
1
0,8
0,6
0,4
0,2
0
Witness
3rd Party
Recipient
Error bars = +/- 1 SE
Pedersen, Kurzban, & McCullough (2013) Proceedings B
Fairness/Moral Wrongness
Error bars = +/- 1 SE
Pedersen, Kurzban, & McCullough (2013) Proceedings B
People Think They Become Angry When They
Witness Mistreatment of Anonymous 3rd Parties
2,5
Anger (controlling envy)
2
Fair
Unfair
1,5
1
0,5
0
Witness Recipient Witness Recipient Witness Recipient
Experiment 1
(N = 270)
Experiment 2a
(N = 538)
Error bars = +/- 1 SE
Experiment 2b
(N = 394)
So What Inputs Does the Revenge
System Appear Designed to Handle
• Perceived costs imposed to self
• Not perceived costs imposed to others
• Not perceptions of moral wrong or unfairness
Third Parties Can Incur Costs Indirectly
If 3rd party’s welfare is interdependent with a
victim’s
•
For example
–
–
–
–
Kin
Friends
Mates
Coalition members
Punishment should be selective
•
Vary as function of
– Victim’s value to 3rd party
– Attacker’s value to 3rd party
– Estimates of several other factors:
• Cost of punishment, p of success, p of future harm, etc.
Experiment 3
Do Third Parties Punish on Behalf of their
Friends?
Pedersen, McAuliffe, & McCullough (in prep)
Method
Stranger
Stranger
Friend
Pedersen & McCullough (in prep)
Method: Write Essays
Stranger
Stranger
Friend
Pedersen & McCullough (in prep)
Method: Review Essays
Stranger
Stranger
Friend
Pedersen & McCullough (in prep)
Method: Read Reviews
“I can understand
why a person
would think like
this.”
Stranger
Stranger
Friend
Pedersen & McCullough (in prep)
Method: Insult
“I can’t believe an
educated person would
think like this. I hope this
person learns something
while at UM.”
Stranger
(Harmon-Jones & Sigelman, 2001)
Stranger
Friend
Pedersen & McCullough (in prep)
Method: Insult
Stranger
Stranger
Insult
Friend
Pedersen & McCullough (in prep)
Method: Insult
Stranger
Stranger
Insult
Friend
Pedersen & McCullough (in prep)
Method: Insult
Insult
Stranger
Stranger
Friend
Pedersen & McCullough (in prep)
Method
Stranger
Stranger
Emotions
+
New task
Friend
Pedersen & McCullough (in prep)
Method: Punishment
Stranger
Stranger
Friend
Audio
Administrator
34
Pedersen & McCullough (in prep)
Results: Punishment
n = 66
n = 64
Pedersen & McCullough (in prep)
Results: Punishment
0,5
n = 69
Punishment (Standardized)
0,4
***
n = 66
n = 64
0,3
0,2
0,1
Insulter
0
Control
-0,1
-0,2
-0,3
-0,4
-0,5
Victim = Self
Victim = Friend
Victim = Stranger
Subject is 3rd Party
Error bars = +/- 1 SE
Pedersen & McCullough (in prep)
Results: Punishment
0,5
Punishment (Standardized)
0,4
n = 69
n = 66
***
**
n = 64
0,3
0,2
0,1
Insulter
0
Control
-0,1
-0,2
-0,3
-0,4
-0,5
Victim = Self
Victim = Friend
Victim = Stranger
Subject is 3rd Party
Error bars = +/- 1 SE
Pedersen & McCullough (in prep)
Results: Punishment
0,5
Punishment (Standardized)
0,4
n = 69
n = 66
***
**
n = 64
0,3
0,2
0,1
Insulter
0
Control
-0,1
-0,2
d = -.18
22% in ROPE
-0,3
-0,4
-0,5
d = .66
0% in ROPE
Victim = Self
d = .43
1% in ROPE
d = -.06
49% in ROPE
Victim = Friend
Victim = Stranger
Subject is 3rd Party
Error bars = +/- 1 SE
Pedersen & McCullough (in prep)
Results: Anger
3
n = 69
n = 66
n = 64
Anger (scale: 0-5)
2,5
2
1,5
Insulter
Control
1
0,5
0
Victim = Self
Victim = Friend
Victim = Stranger
Subject is 3rd Party
Error bars = +/- 1 SE
Pedersen & McCullough (in prep)
Results: Anger
3
n = 69
n = 66
n = 64
***
Anger (scale: 0-5)
2,5
2
1,5
Insulter
Control
1
0,5
0
Victim = Self
Victim = Friend
Victim = Stranger
Subject is 3rd Party
Error bars = +/- 1 SE
Pedersen & McCullough (in prep)
Results: Anger
3
n = 69
n = 66
***
***
n = 64
Anger (scale: 0-5)
2,5
2
1,5
Insulter
Control
1
0,5
0
Victim = Self
Victim = Friend
Victim = Stranger
Subject is 3rd Party
Error bars = +/- 1 SE
Pedersen & McCullough (in prep)
Results: Anger
3
Anger (scale: 0-5)
2,5
n = 69
n = 66
n = 64
***
***
**
d = .89
0% in ROPE
d = .60
0% in ROPE
d = .0
61% in ROPE
2
1,5
Insulter
Control
1
0,5
0
Victim = Self
Victim = Friend
Victim = Stranger
Subject is 3rd Party
Error bars = +/- 1 SE
ROPE = Region of Practical Equivalence
Pedersen & McCullough (in prep)
What Systems Regulate Third-Party Punishment?
The Welfare Tradeoff Ratio (WTR)
Proposed internal regulatory variable for social behavior
Weights value of another’s welfare relative to self
Possible inputs:
•
•
•
•
•
•
•
Relatedness
Past interaction experience
Estimates of future interactions
Shared parental investments
Strength and fighting ability
Mate value
Mutual value
(Tooby & Cosmides, 2008; Tooby et al., 2008)
Welfare Tradeoff Ratio (WTR)
Assume
indifference is at
the midpoint ($50),
implying that x’s
WTR for y =
$50/$75 = 0.67.
Adapted from Jones & Rachlin (2009)
Estimating Net Costs
Harm
Attacker
Victim
BAttacker
CVictim
Net C3rd Party =
Estimating Net Costs
Harm
Attacker
Victim
BAttacker
CVictim
Net C3rd Party = (CVictim * WTRVictim)
Estimating Net Costs
Harm
Attacker
Victim
BAttacker
CVictim
Net C3rd Party = (CVictim * WTRVictim) - (BAttacker * WTRAttacker)
Estimating Net Costs
Harm
Attacker
Victim
BAttacker
CVictim
Net C3rd Party = (CVictim * WTRVictim) - (BAttacker * WTRAttacker)
Predict punishment and emotional reactions
Experiment 4
Do WTRs Predict Third-Party Punishment?
Pedersen, McAuliffe, Shah, & McCullough (in prep)
Methods
Undergraduates and Mechanical Turk users
•
Total N = 918
“Please think of the last situation you can recall in which
you witnessed someone attack, insult, or otherwise
mistreat another person.”
Coded :
•
•
Punishment (costs inflicted)
Intervention (intervening in any way)
WTRs for victim and attacker + emotional responses
Pedersen, McAuliffe, Shah, & McCullough (in prep)
Results: Punishment
Pedersen, McAuliffe, Shah, & McCullough (in prep)
Results: Punishment
Model-Predicted Punishment
0,1
0,09
0,08
bWTR Victim = 1.45**, OR = 4.28
bWTR Attacker = -1.58ns, OR = .21
Probability
0,07
0,06
0,05
0,04
0,03
0,02
0,01
0
0,00
0,03
0,13
0,27
0,40
0,53
0,67
0,80
0,93
1,07
1,13
WTR toward Victim
Pedersen, McAuliffe, Shah, & McCullough (in prep)
Results: Punishment
Model-Predicted Punishment
1
0,9
0,8
bWTR Victim = 1.45**, OR = 4.28
bWTR Attacker = -1.58ns, OR = .21
Probability
0,7
0,6
0,5
0,4
0,3
0,2
0,1
0
0,00
0,03
0,13
0,27
0,40
0,53
0,67
0,80
0,93
1,07
1,13
WTR toward Victim
Pedersen, McAuliffe, Shah, & McCullough (in prep)
Results: Intervention
Model-Predicted Intervention
1
0,9
0,8
bWTR Victim = 1.20***, OR = 3.31
bWTR Attacker = -.22ns, OR = .81
Probability
0,7
0,6
0,5
0,4
0,3
0,2
0,1
0
0,00
0,03
0,13
0,27
0,40
0,53
0,67
0,80
0,93
1,07
1,13
WTR toward Victim
Pedersen, McAuliffe, Shah, & McCullough (in prep)
Results: Emotions
Anger toward attacker (scale: 0-5)
• Intercept = 2.26***
• WTRvictim = 1.48***, β = 0.39
• WTRattacker = -1.21***, β = -0.24
Empathy toward victim (scale: 0-5)
• Intercept = 2.56***
• WTRvictim = 1.60***, β = 0.43
• WTRattacker = -.54**, β = -0.11
These results replicated in a Japanese sample
Replications under way in Indonesia and Venezuela
Pedersen, McAuliffe, Shah, & McCullough (in prep)
“The paucity of ethnographic
references to remorse and
forgiveness suggests either an
appalling oversight by
generations of anthropologists,
or it could alert us to the
modernist and western nature of
the concepts under
consideration.”
~Nancy Scheper-Hughes (1999)
HRAF Probability Sample (a globally stratified sample of world
societies, with an emphasis on small-scale societies)
53 of the 60 societies showed evidence of forgiveness,
reconciliation, or both in their ethnographic materials
93%: Very close to Donald Brown’s (somewhat arbitrary) cut-off for
declaring a trait a “statistical human universal”
McCullough, 2008, Beyond Revenge
What Adaptive Problem Did Forgiveness
Evolve to Address?
• Maintaining valuable relationships—despite inevitable conflicts of
interest
• Valuable relationships
–
–
–
–
Kin relations
Mates
Exchange partners
Friends
• In non-human primates, reconciliation is most common among
genetic relatives and “friends.”
Key computational problem for a forgiveness
mechanism: Which relationships are worth
reconciling in light of potential value and
potential risk of further exploitation?
Key computational problem for a forgiveness mechanism: Which
relationships are worth reconciling in light of potential value and
potential risk of further exploitation?
Perceived Relationship
Value
Integrating Function
Perceived Risk of
Future Exploitation
Forgiveness
Conciliatory Gestures:
Cultural Universals for Promoting Forgiveness
•Examples:
•Compensation, gift-giving
•Apologies
•Promises of forbearance
•Surrender of power to harm
•Sharing of food or goods
•Physical touch
•Self-abasing displays
•Explicit requests for forgiveness
•Reliable inhibitors of revenge/elicitors of forgiveness
•How do they work? Perhaps by influencing relationship
value/exploitation risk
To Forgive Adaptively, People Must Integrate Info
About Relationship Value and Exploitation Risk
Burnette, McCullough et al., 2012, PSPB
A Short-Term Longitudinal Study
• N = 356 people who incurred significant interpersonal harm
< 10 days
• Time 1: Lab visit for Time 1 measures of conciliatory
gestures, relationship value, exploitation risk
• Time 2: Lab visit for follow-up measures, plus speech task
(from which we captured facial expressions of anger, angerrelated word use, and self-reported anger post-speech)
• Throughout: 21-days of self-report forgiveness measures
• Two-wave cross-lagged models to estimate the influence of
conciliatory gestures on forgiveness and anger, and indirect
effects via relationship value & exploitation risk
Michael E. McCullough et al. PNAS 2014;111:11211-11216
©2014 by National Academy of Sciences
Two subjects’ scores (slightly altered to preserve anonymity) on the TRIM inventory, with leastsquares lines of best fit.
Michael E. McCullough et al. PNAS 2014;111:11211-11216
©2014 by National Academy of Sciences
Path model for predicting initial status and linear change (i.e., forgiveness) in participants’ TRIM
scores.
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Michael E. McCullough et al. PNAS 2014;111:11211-11216
©2014 by National Academy of Sciences
*
Path model for predicting three measures of participants’ anger toward their transgressors.
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Michael E. McCullough et al. PNAS 2014;111:11211-11216
©2014 by National Academy of Sciences
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