Detecting defectors when they have incentives to

manipulate their impressions.

Toko Kiyonari (Aoyama Gakuin University)J. Schug, M. Shinada, T. Takahashi, &T. Yamagishi

(Hokkaido University)

13th International Conference on Social DilemmasKyoto, 20-24th August, 2009

Do people discriminate cooperators from

defectors?The human capacity of cheater detection is of great significance in Evolutionary psychology.

Human evolved sensitivity to cues of cheaters and cooperators (e.g., Cosmides & Tooby, 1992).

There is evidence suggesting that people can visually discriminate

defectors from cooperators. Brown, Palameta, and Moore (2003) found a significant altruist detection effect in response to video taped storytelling.

Verplaetse, Vanneste, Braeckman (2007) show that participants could discriminate defectors from cooperators when they saw event-related pictures taken during the decision-making moment of a proper round.

Frank, Gilovich, and Regan (1993) found that participants were able to predict individual behavior in a one-shot PD when they had a 30-min "get-acquainted" meeting before the game.

Purpose

In this study, we examine if participants can successfully tell cooperators from defectors when defectors have incentives to conceal or disguise their facial or verbal expressions.

Except for Frank's (1988) study in which participants could make promises for their game behavior, however, these results were obtained only in situations where defectors had no incentives to deceive others.

Summary of methodsThe first-player of a “semi-sequential” PD game made a cooperation-defection decision, and was given an opportunity to send a video-taped message to the second- player before the second-player made his or her decision.The second-player saw the video message (with no sound), but was not informed of the first-player’s actual choice, and then made a decision.The second-player also judged if the first-player cooperated or defected before actually making a decision (First Study).Different groups of judges saw the same video (without sound) or transcripts of the verbal messages (without visual presentations) and judged if the first-players cooperated or defected (Second Study).

Summary FindingsIn a situation where defectors had an incentive to conceal or disguise their facial and verbal expressions,Second-players were not able to

discriminate defectors from cooperators in the PD game.

However, they were able to identify “hard-core defectors” who defected both in PD and Stag Hunt (one type of coordination game) games.

And yet, another group of judges (third party) were unable to detect even hard-core defectors.

Flow of the experiment: 1st-players~

#4:They played a “semi-sequential” Prisoners’ Dilemma (PD) Game as a 1st-player

#6: They took a video message to their potential partner.

#9:They played a Stag Hunt (SH) Game as a 1st-player.

#1: They answered a Pre-exp. questionnaire (Trust, SVO, Machiavellianism) .

#2: A video tape was taken while they were reading a tale of “The country mouse and the city mouse” written by Aesop.

#3: Their saliva- sample was taken-1.

#5: They answered a Post-exp. questionnaire-1

#7: Their saliva sample was taken-2

#8: They answered a Post-exp. questionnaire-2

#10: They answered a Post-exp. questionnaire-3&4

Fin.

Mon Tue Wed Thur Fri

1st-Players

PD

SH

Saliva-sample

Saliva-sample

Storytelling

Played a semi-sequential PD

Video message

Played a SH

Mon Tue Wed Thur Fri Sat Sun

1st-Players

2nd-Players

PD

SH

Saliva-sample

Saliva-sample

Storytelling

Played a semi-sequential PD

Video message

Played a SH

Judgment

& decision

PD

SH

You\1200

Partner \1200

Partner\0

Partner \1800

You\1800

Partner \600

You\0

You\600

L

S

K P

YOU

PartnerIncentive structure of the PD game

In this game, the first-player made the decision between L (i.e., cooperate) and S (i.e., defect), and then the second-player made the same decision without knowing the choice of the first-player (as in the simultaneously played game). The first-players knew their partner would participate in this experiment later approximately within a week. Thus their reward would be paid as their partner has made their decision.

Exchange rate$1 ≈ \ 94€1 ≈ \134₤1 ≈ \156

Sending a video message

➢They were informed that the video tape of their message may be presented to their partner either with or without voices.

➢After the decision in a PD, the first-players were given a chance to send a video message (30 seconds long) to the second-player. They were told that the second-player would make his/her decision after seeing the video.

➢When the first players made the C-D decision, they did not know that they would have this opportunity to send a message.

Mon Tue Wed Thur Fri

1st-Players

PD

SH

Saliva-sample

Saliva-sample

Storytelling

Played a semi-sequential PD

Video message

Played a SH

You\700

Partner \700

Partner\100

Partner \500

You\500

Partner \500

You\100

You\500

T

Q

M X

YOU

PartnerIncentive structure of SH game

The SH is a coordination game (e.g., Skyrms, 2004) where cooperation is the best choice insofar as the other cooperates as well.

The first-player was not given a chance to give a video message.

Flow of the experiment: 2nd-player~

#4: They played a Stag Hunt (SH) Game as a 2nd-player.

#1: They answered a Pre-exp.questionnaire (Trust, SVO, Machiavellianism) .

#2: The 2nd-player watched video messages of 10-14 1st-players, and judged whether each of them cooperated or defected.Then, they played the game as second-players.

#3: They answered a Post-exp. questionnaire-1.

#5: They answered a Post-exp. questionnaire-2.

Fin.

#6: They participated in a detection experiment of fake or not-fake smile.

#7: They answered a Post-exp. questionnaire-3.

Mon Tue Wed Thur Fri Sat Sun

1st-Players

2nd-PlayersJudgment

& decision

PD

SH

PD with video messages

\1200

\1200

\0

\1800

\1800

\600

\0

\600

L

S

K P

Partner

You

•Each second-player was shown video clips of 10-14 first-players, without sound, and decided whether to cooperate (K) or defect (P) with each of these first players, on the assumption that he/she would be paid for the outcome of the game with one randomly chosen partner.

In addition, the second-player was asked to predict if each of the first-players cooperated or defected before their decision.

PD with video messages

Did the person choose “L” (cooperation) or “S” (defection)?I am going to choose “K” (cooperation) or “P” (defection) with this person.

Mon Tue Wed Thur Fri Sat Sun

1st-Players

2nd-PlayersJudgment

& decision

PD

SH

Partner\700

You \700

You\100

You \500

Partner\500

You \500

Partner\100

Partner\500

T

Q

M X

Partner

YouIncentive structure of SH game

The second-player did not see the video face of the first-player.

ParticipantsFirst StudySeventy-nine participants played the role of first-

players in a “semi-sequential” PD and SH games, and 79 participants played the role of second-players in those games.

They played with partners of the same sex.

Six were eliminated from today’s report because they received different manipulations .

Second StudyThirty participants from another university

judged all 73 video tapes of the first players.

1st-players’ choices

• Twenty-six out of 73 (35.6%) first-players cooperated in the PD.

• Thirty-seven out of 73 (50.7%) first-players cooperated in the SH.

• Thirty-one out of 73 (42.5%) defected in both games. Hard-core defector

• No sex difference in PD cooperation (M:34.2% vs. F:37.5%).

• No sex difference in SH cooperation (M:56.1% vs. F:43.8%).

Basic results

Cooperators Defectors

The first-players who actually cooperated in PD were judged to have cooperated, on average, by 54.6% of the second-players who saw their videos.The first-players who actually defected in PD were judged to have cooperated, on average, by 49.9% of the second-players who saw their videos.

54.6% > 49.9%, t(71)=.99, p=.32

Degree of being judged as a cooperator

However, in this study, the second-players saw different numbers of cooperators and defectors , thus we need to use adjusted judgment score for the analysis.

First-players were judged only by the second-players in the same group.

Group 1: 6/10, Group 2: 2/10, Group 3: 4/10, Group 4: 2/11,

Group 5: 7/12 (6 were eliminated from today’s report),

Group 6: 7/12, Group 7: 4/14

Numbers of cooperators in each video set:

Adjusted Judgment Score: Individual first player’s deviation score adjusted for the group mean (deviation of cooperation judgment for each target from mean cooperation judgment )

Regression Analysis 1:Dependent variable: Adjusted judgment score

Model 1 b t pIntercept -0.034 -1.14 0.260Actual behavior (PD) 0.006 0.12 0.902Actual behavior (SH) 0.063 1.37 0.174

Model 2 b t pIntercept -0.131 -0.90 0.373Actual behavior (PD) 0.046 0.89 0.379Actual behavior (SH) 0.081 1.80 0.079Encode -0.050 -2.32 0.023Activity 0.040 2.14 0.036Prosocial -0.002 -0.41 0.682

If the actual behaviors in PD and SH predicted the judgment, i.e., If the judgment reflects actual behaviors.

Actual Behavior in PD

Actual Behavior in SHJudgment

Controlling for some individual differences

Encode: self-report encode abilityActivity: self-report willingness to get new acquaintances actively and behave socially to anyone Prosocial: Degree of pro-sociality (Social Value Orientation)

Regression Analysis 2:Dependent variable: Adjusted judgment score

Model 1 b t pIntercept 0.033 1.24 0.220Hard-core D -0.078 -1.90 0.062Model 2 b t pIntercept -0.047 -0.33 0.743Hard-core D -0.119 -2.85 0.006Encode -0.050 -2.38 0.020Activity 0.0429 2.32 0.023Prosocial -0.001 -0.18 0.860

Encode: self-report encode abilityActivity: self-report willingness to get new acquaintances actively and behave

socially to anyone Prosocial: Degree of pro-sociality (Social Value Orientation)

We then examined whether the first- player was a hard-core defector or not predict the judgment.

The second-players’ judgment reflected the actual behavior of the first player—whether the first player was a hard-core defector or not.

When the third-party was the judge…

Defectors in PD game were judged that they had cooperated, on average, by 16.68 out of 30 raters. Cooperators in PD game were judged that they had cooperated, on average, by 16.85 out of 30 raters.

PD gameDefectors

(N=47)Cooperators

(N=26)

How many raters judged the target as a cooperator?

16.68(sd=5.45)

16.85(sd=5.80)

Thirty raters from another university judged each of the 73 first players if the video taped person cooperated or defected.

They couldn’t discriminate cooperators and defectors in the PD game.

When the third-party was the judge…

Stag Hunt GameDefectors

(N=36)Cooperators

(N=37)

How many out of 30 raters? 16.69

(sd=4.77)16.78

(sd=6.25)

They couldn’t discriminate cooperators and defectors in the SH game.

Hard-coreDefectors

(N=42)Else

(N= 31)

How many out of 30 raters?

16.76(sd=5.96)

16.71(sd=5.00)

When judges didn’t have monetary incentive to discriminate between cheaters and cooperators, the third-party judges could not detect even hard-core defectors.

Did the third-party judges see differences in the cooperators’ and

defectors’ messages?

Criterion: The message implies that the message sender has cooperated Yes/No

Thirty raters judged each first player’s transcribed message on the following criteria.

Criterion: The message sender equivocates if he/she has cooperated or defected Yes/NoCriterion: The message sender is trying to communicate that he/she has cooperated Yes/NoCriterion: The message is a lie if the message sender has actually defected Yes/No

Are cooperators’ messages rated differently from defectors’ messages by 30 raters?

How many raters checked “YES” on average?

Criterion Defectors’ message

Cooperators’ message

The message implies that the message sender cooperated 7.98 11.11 ns.

The message sender sent a message which could be interpreted either way

11.34 11.12 ns.

The message sender is trying to communicate that he/she has cooperated

8.34 11.42 ns.

The message would be a lie if the message sender had actually defected

7.51 9.42 ns.

Did the third-party judges see differences in the cooperators’ and defectors’ messages

30 raters read the first player’s message, and judged whether he/she cooperated or defected (or unsure)More judges correctly rated actual cooperators as cooperators (M = 9.85) than as defectors (M=6.54), though the difference was not significant (t(25)=1.34, p=.19).13.38 raters selected “unsure”

The difference between differences was marginally significant (t(71)=1.71, p=.0911).

These results suggest that the contents of the verbal messages may be used to discriminate cooperators from defectors, but they may not be an efficient means of cooperator/cheater detection.

More judges correctly rated the actual defectors as defectors (M = 9.74) than cooperators (M=7.30), though the difference was not significant (t(46)=1.17, p=.25).12.87 raters selected “unsure”

ConclusionWhen the players have incentives to hide intentions or manipulate impressions, even motivated judges (whose monetary gain depended on the accuracy of cheater/ cooperator detection) could not distinguish defectors from cooperators either in PD or SH game.

However, they seem to be able to discriminate hard-core defectors from others.Yet, when judges had no monetary incentives to detect targets’ choice, they couldn’t detect even hard-core defectors. The content of the messages were also not sufficient help to tell defectors from cooperators.

s

Conclusion

Needless to say, more controlled judgment experiment is required to conclude…

As a final remark…Majority of our cooperators didn’t broadcast their cooperation. This may or may not be based on Japanese culture. We will see…

Thank you!

Personality traits itemsActivity (alpha=.83): I seek to make new acquaintances.

(積極的に新しい知り合いを増やしていきたい )It is important to make new acquaintances for enhancing my future chances.

(自分の可能性を広げるために、新しい知り合い作りは重要だ )I think gaining acquaintances is useful for my future in many respects.

(知り合いを増やすことは、なにかにつけて将来自分の役に立つと思う )For succeeding in one’s life, it is necessary to jump at anywhere even no one knows you.

(人生で成功するためには、知らない人しかいないところにでも、積極的に出て行く必要がある )I want to behave socially to anyone.

(誰に対しても社交的に振る舞いたい )One should present his/her positive aspects to others.

(自分の良いところは積極的に他人にアピールすべきだ )

Encode (alpha=.70):I am good at accurately telling my own feelings to others.

(自分の気持ちを正確に相手に伝える )I am good at leading conversation.

(会話をうまくすすめる )I can express my own feelings easily.

(感情を素直にあらあす )I am good at using body language to explain my thoughts and feelings.

(身振りや手振りをうまく使って表現できる )

Correlations between items and behavior

Trust Caution Prosocial Individual Machiavellian Activity Encode Altruism Scale

AdjustedestC

PD r=.15 r= -.17 r=.42 r= -.41 r=.32 r= -.22 r=.20 r=.07 r=.10

D=0, C=1 p=.22 p=.14 p=.0002 p=.0003 p=.0056 p=.07 p=.09 p=.57 p=.42

SH r=.20 r= -.10 r=.15 r= -.19 r=.14 r= -.11 r=.23 r=.07 r=.19

D=0, C=1 p=.08 p=.39 p=.21 p=.10 p=.24 p=.36 p=.047 p=.54 p=.11

Hard-core r= -.20 r=.11 r=-.17 r=.20 r=-.12 r=.19 r= -.22 r= -.004 r= -.22

D=1 p=.09 p=.34 p=.15 p=.09 p=.31 p=.11 p=.059 p=.97 p=.0617

Did predictions based on messages differ from cooperators and defectors?

Defectors CooperatorsHow many raters judged the target “cooperated”

7.30(sd=8.10)

9.85(sd=9.10) ns.

How many raters judged the target “defected”

9.74(sd=8.37)

6.54(sd=5.21) p=.0479

How many raters judged the target is “hard to judge” (because of no information about the decision)

12.87(sd=8.10)

13.38(sd=7.97) ns.

Thirty raters judged each transcribed message whether the target cooperated or defected based on verbal meanings in each message.

These suggest that at least some of defectors probably tried to manipulate their impression during their message video. Furthermore, at least some of cooperators’ message were misinterpreted and judged as defectors…

Adjusted judgment score for cooperationSecond Player's Judgment

First Player

Choice in PD P2_1 P2_2 P2_3 P2_4 P2_5 P2_6 P2_7 P2_8 P2_9 P2_10

Proportion to be

judged C

Deviation from

AverageP1_1 D 1 0 0 1 1 0 0 1 1 0 0.5 -0.04P1_2 C 1 1 0 0 1 1 1 1 1 1 0.4 -0.14P1_3 D 1 1 0 0 1 1 0 0 0 0 0.6 0.06P1_4 D 1 1 0 1 1 1 1 0 0 0 0.8 0.26P1_5 C 1 1 1 0 1 1 1 0 1 1 0.8 0.17P1_6 D 1 1 1 1 1 1 1 0 1 0 0.4 -0.23P1_7 C 0 1 0 0 1 0 0 1 0 0 0.6 -0.03P1_8 C 0 1 0 1 1 0 1 0 0 0 0.2 -0.43P1_9 C 0 1 0 0 1 1 0 1 1 1 0.7 0.07

P1_10 C 0 0 0 0 1 0 1 0 0 0 0.7 0.07Average 0.6 0.8 0.2 0.4 1.0 0.6 0.6 0.4 0.5 0.3 0.54 0.035

Defectors in PD (n=47): -0.012 (sd=0.177)Cooperators in PD (n=26): 0.023 (sd=0.178), t(71)=.82, p=0.415

Defectors in SH (n=36): -0.033 (sd=0.155)Cooperators in SH (n=37): 0.0325 (sd=0.193), t(71)=1.61, p=0.112

Hardcore Defectors (n=31): -0.045 (sd=0.158)Rest of participants (n=42): 0.0338 (sd=0.188), t(71)=1.90. p=0.0617