joanna schug 1 toshio yamagishi 1 david matsumoto 2 yutaka horita 1 kemberlee bonnett 2

Emotional Expressivity as a Signal of Cooperativeness:

An Investigation of Facial Expressions of Emotion in the Ultimatum Game

Joanna Schug1

Toshio Yamagishi1

David Matsumoto2

Yutaka Horita1

Kemberlee Bonnett2

1: Hokkaido University 2: San Francisco State University

International Conference on Social Dilemmas, Kyoto, Japan

Emotional Expressions as signals of cooperation

2

• Cooperation among non-kin may evolve in a population when reliable signals of cooperative tendency exist, instilling cooperators with the ability to selectively seek out other cooperators as interaction partners (Dawkins, 1976; Frank, 1988, 2001;Hamilton, 1964)

• Many studies have examined whether cooperators can be visually identified – Physical traits (Takahashi et al., 2006, Yamagishi et al.,

2003) – Facial expressions of emotion (Boone & Buck 2003;

Frank 1988; Gazzaniga & Smylie, 1990; Krumhuber et al., 2007; Mehu, Little, & Dunbar, 2007; Oda et al., 2009; Scharlemann, Eckel, Kacelnik & Wilson, 2001) Genuine positive emotion: Duchenne smiles

Duchenne smiles

3

• Duchenne smiles involve the facial musculature (orbicularis occuli) which surround the eyes– Difficult to intentionally control – Correlated with subjective positive experience

(Frank, Ekman, & Friesen, 1993; Hess, Banse, & Kappas, 1995; Keltner & Bonanno, 1997 )

• Non-Duchenne smiles only involve the zygomatic major muscle (pulls back corners of mouth)– Possible to intentionally control– Not correlated with subjective positive

experience (Bonanno et al., 2002, Keltner, 1995)

Because genuine expressions of positive emotion cannot easily be faked, they can reliably signal cooperativeness

Duchenne smiles as a signal of cooperativeness

4

• Altruists/Cooperators display higher levels of genuine positive emotion (= Duchenne smiles) than egoists– When talking about personal experiences

(Shelley & Kuhlman, 2007)– When engaged in natural conversation (Oda et

al., 2009)– Reading aloud a fairy-tale (Brown et al., 2003)– Sharing a reward with a friend (Mehu, Grammer &

Dunbar, 2007)

Duchenne smiles signal cooperativeness


5

• However, Duchenne smiles do not always signal cooperation…– Pre-school children playing a Prisoner’s Dilemma game

show Duchenne smiles when successfully defecting on their partner (Matsumoto et al., 1986)

– Olympic athletes show Duchenne smiles when defeating an opponent (Matsumoto & Willingham, 2007)

– Duchenne smiles were positively related to altruistic tendency only when they were displayed in situations requiring sharing, but not during a waiting period before the experiment (Mehu, Grammer & Dunbar, 2007)

• The situation in which the emotion is displayed is important


Can negative emotion signal cooperative intent?

6

• Can “negative” emotional expressions signal cooperative tendency?– Moral Disgust: One recent study found that facial musculature

relevant to the expression of disgust was activated in response to unfair offers in an ultimatum game

(Chapman, 2009, Science)– Many negative expressions of emotion can be just as (if not more) difficult to intentionally falsify than Duchenne smiles

(Ekman, 2003; Ekman, Roper, & Hager, 1980; Porter & ten Brinke, 2008) Same logic holds

Emotional Expressivity as a signal of Cooperation

7

• Alternative explanation: Emotional expressivity– Emotional expressivity in itself may serve as a marker for

cooperative behavior and trustworthiness (Boon and Buck, 2003) • Facilitates mind-reading, allowing for mutual selection among

cooperators• Expressivity in itself difficult to falsify• Emotionally expressive individuals are less able to deceive others

Makes defection a bad strategy

– Tendency for cooperators in previous studies to show higher levels of positive emotion may be due to the tendency for cooperators to openly express their emotion

• Previous studies have only examined specific emotions in positive/ neutral situations

The current study

• In this study, we examine the facial expressions of emotion of cooperators and non-cooperators as they face a negative situation– Unfair offers in the Ultimatum Game

• We identify cooperators using both a behavioral and measurement and SVO

• If cooperators are more emotionally expressive, they should display higher levels of not only positive but also negative emotion

Method

9

• 20 male participants from Hokkaido University

• Truncated Ultimatum Game (Falk et al., 2003)– Proposer makes a binary choice

(500:500 or 800:200) – Receiver decides whether to accept or

reject the offer• If he accepts the offer, both players

receive the amount offered by the proposer

• If he rejects the offer, both players receive nothing

Method

10

• Participants played the Ultimatum Game three times (each time with a new player, anonymity assured)

• In the first two games, participants played the role of the responder, facing offers from two “proposers”1. Intentional unfair offer

• Choices were: \500(proposer)/ \500(participant) 　 \800(proposer)/ \200(participant)

2. Unintentional unfair offer • Both choices were \800(proposer)/ \200(participant)

Intention of the proposer is unclear• In the last game, the participant played the role of

the proposer• Chose between \800(self) / \200(other) and \500

each

Identification of Cooperators

11

• Behavioral identification of cooperators:– Those who selected the fair (500/500) offer as a

proposer in the third round of the ultimatum game11/20 participants selected the fair offer

• Social Value Orientation:– Ring Measure of Social Value Orientation (SVO)

Liebrand, 1984– Classified as pro-socials and pro-selfs – 9/20 participants classified as pro-

socials

Coding of Facial Expressions

12

• Facial expressions videotaped through the monitor display (participants were aware they were being recorded, however the camera itself was relatively obscured)

• Facial Action Coding System (FACS)– Only comprehensive, anatomically based system for

scoring facial expressions– EMFACS system:

• Only codes action units relevant to emotional signaling

• Identifies eight emotional categories: anger, disgust, fear, sadness, contempt, duchenne

smile, non-duchenne smile, and surprise

Time spans coded

• We focus the analysis on the time period from when the unfair offer was displayed on the screen, until the participant decided to accept or reject the unfair offer. – Response phase (approx. 15 seconds)– Negative event intended to elicit negative

emotion• We also coded the waiting period

before/after the response phase– Pre- response phase (15-25 seconds) – Post response phase (30 seconds)

* Because each phase varies in length, we divide emotion frequency by the length of each phase and use the resulting per-second frequencies in the analysis

Results (Fair vs. Unfair proposers)

14Decision-making phase of first two games (intentional/unintentional) pooled

.00

.01

.02

.03

.04

.05

.06

.07

.08

Anger Disgust Fear Sadness Contempt DuchenneSmile

Non-Duchenne

Surprise

Per-s

econ

d fre

quen

cy o

f em

otion

al e

xpre

ssio

n

Unfair proposer

Fair Proposer

Ultimatum game

15

• May not be a pure measure of cooperation– Even those who are solely concerned with their

own welfare may propose a fair offer if they believe their offer will be rejected

– Thus, we qualified the behavioral measure with the measure of SVO

• 3/11 fair proposers were identified as pro-selfs• 1/9 unfair proposers was identified as a pro-social

We focus our examination on those who were consistently identified as cooperators (pro-socials) and non-cooperators (pro-selfs)

Consistent cooperators

16Decision-making phase of first two games (intentional/unintentional) pooled

.00

.01

.02

.03

.04

.05

.06

.07

.08

Anger Disgust Fear Sadness Contempt DuchenneSmile

Non-Duchenne

Surprise

Per-s

econ

d fr

eque

ncy

of e

moti

onal

exp

ress

ion

Non-cooperator

Cooperator

Because we had predicted that differences between cooperators and non-cooperators would be most pronounced in the response phase (when participants faced an unfair offer) we examined the differences in the total frequency of emotional expressions shown in all three game phases: – Pre-response Phase– Response Phase (P’s faced unfair offers)– Post-response Phase

As predicted, we found a significant interaction between proposer type (cooperator/non-cooperator) and game phase (Pre, Response, Post) on the total amount of emotional expressions observed. F (2,28)=11.21, p= .0003

Facial expressions displayed in each phase

18

0

0.05

0.1

0.15

0.2

Non-cooperator

Cooperator Non-cooperator


Cooperator

Pre- Response Post-

Exp

ress

ions

obs

erve

d pe

r sec

ond

ContemptSadnessFearDisgustAngerSurpriseNon-DuchenneDuchenne


Phase

0

0.05

0.1

0.15

0.2

Non-cooperator



Cooperator

Pre- Response Post-

Exp

ress

ions

obs

erve

d pe

r sec

ond



19Phase

0

0.05

0.1

0.15

0.2

Non-cooperator



Cooperator

Pre- Response Post-

Exp

ress

ions

obs

erve

d pe

r sec

ond


20


Phase

0

0.05

0.1

0.15

0.2

Non-cooperator



Cooperator

Pre- Response Post-

Exp

ress

ions

obs

erve

d pe

r sec

ond


21


Participants displayed more facial expressions during the decision-making phase (in which they faced unfair offers in the Ultimatum Game) than in the waiting periods before and after the decision-making phase.

Phase

22

0

0.05

0.1

0.15

0.2

Non-cooperator



Cooperator

Pre- Decision-Making Post-

Exp

ress

ions

obs

erve

d pe

r sec

ond


d=.99, p=.07,

ns ns

Positive (Duchenne Smile)

0

0.05

0.1

0.15

0.2

Non-cooperator



Cooperator

Pre- Response Post-

Phase

23

0

0.05

0.1

0.15

0.2

Non-cooperator



Cooperator


Exp

ress

ions

obs

erve

d pe

r sec

ond


d=1.28, p<.05

ns ns

Neutral (Non-Duchenne, Surprise)

0

0.05

0.1

0.15

0.2

Non-cooperator



Cooperator

Pre- Response Post-

Phase

24

0

0.05

0.1

0.15

0.2

Non-cooperator



Cooperator


Exp

ress

ions

obs

erve

d pe

r sec

ond

ContemptSadnessFearDisgustAngerSurpriseNon-DuchenneDuchenne d=1.13, p<.05

nsns

Negative (Anger, Contempt, Disgust, Fear, Sadness)

0

0.05

0.1

0.15

0.2

Non-cooperator



Cooperator

Pre- Response Post-

Phase

Summary

25

• As in previous studies, cooperators showed higher levels of positive emotion (duchenne smiles) 　

• However, cooperators also showed higher levels of neutral (e.g., non-duchenne smiles, surprise) and negative (e.g., sadness, disgust, contempt) facial expressions of emotion.

– These differences were most apparent when participants were faced with a negative situation (unfair offers in the UG)

Implications

26

• Previous studies have mainly focused on the display of genuine positive emotion as a signal of cooperation

• Results of this study suggest that this finding may stem from the tendency for cooperators to openly display all emotion– Should lead to higher levels of positive emotion

in situations requiring cooperation– Should simultaneously lead to higher levels of

negative emotion in negative situations

Limitations

27

• No incentives to falsify emotion– Emotions displayed in privacy, no interaction

with other participants– Future studies should examine situations in

which participants have incentives to mask and/or falsify their emotion

• Uncertain whether non-cooperators feel less emotion, or whether they are masking their expressions

Thank you very much for your attention!

joanna schug 1 toshio yamagishi 1 david matsumoto 2 yutaka horita 1 kemberlee bonnett 2

Documents