1. International Conference on Social Dilemmas, Kyoto, Japan
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

2. Emotional Expressions as signals of cooperation
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 2 2

3. Duchenne smiles
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 3 3

4. Duchenne smiles signal cooperativeness
Duchenne smiles as a signal of cooperativeness
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 4 4

5. Duchenne smiles as a signal of cooperativeness
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 5 5

6. Can negative emotion signal cooperative intent?
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 6 6

7. Emotional Expressivity as a signal of Cooperation
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
Alternative explanations: 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
We suspect that 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 7 7

8. 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

9. Method 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 9 9

10. Method
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 10 10

11. Identification of Cooperators
Behavioral identification of cooperators:
Those who selected the fair (500/500) offer as a proposer in the third round of the ultimatum game
11/20 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 11 11

12. Coding of Facial Expressions
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 12 12

13. 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

14. Results (Fair vs. Unfair proposers)
Decision-making phase of first two games (intentional/unintentional) pooled 14 14

15. Ultimatum game 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) 15 15

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

17. Facial expressions displayed in each phase
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

18. Facial expressions displayed in each phase18
Phase 18

19. Facial expressions displayed in each phase19
Phase 19

20. Facial expressions displayed in each phase20
Phase 20

21. Facial expressions displayed in each phase
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. 21
Phase 21

22. Positive (Duchenne Smile)
d=.99, p=.07, ns ns 22
Phase 22

23. Neutral (Non-Duchenne, Surprise)
d=1.28, p<.05 ns ns 23
Phase 23

24. Negative (Anger, Contempt, Disgust, Fear, Sadness)
d=1.13, p<.05 ns ns 24
Phase 24

25. Summary
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) 25 25

26. Implications
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 26 26

27. Limitations 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 27 27

28. Thank you very much for your attention!