Irrational Economic Decision Making in
Schizophrenia:
Evidence from the Ultimatum Game
Korean Neuropsychiatric Association
2008.10.23, 03:25p.m.
Kyongsik Yun, Ph.D. Candidate
Bio and Brain Engineering
KAIST
yunks@kaist.edu

Questions to be asked
• Is the Ultimatum game behavior of schizophrenia
different from that of normal controls?
• Does time frequency analysis of EEGs show
impaired decision making in schizophrenia?
• Does phase synchronization of EEGs show
impaired decision making in schizophrenia?
2

3

What are the temporal dynamics of
social interaction?
proposer responder
4

What are the temporal dynamics of
social interaction?
proposer responder
1. Make an offer: 9:1
(send emotional cue)
Reward anticipation
(NAcc)
5

What are the temporal dynamics of
social interaction?
proposer responder
1. Make an offer: 9:1 2. Conflict btwn emotion & cognition
(send emotional cue) ACC, Ins, dlPFC activation (interaction)
Reward anticipation
(NAcc)
6

What are the temporal dynamics of
social interaction?
proposer responder
1. Make an offer: 9:1 2. Conflict btwn emotion & cognition
(send emotional cue) ACC, Ins, dlPFC activation (interaction)
Reward anticipation
(NAcc) 3. Make a decision (reject: Ins)
7

What are the temporal dynamics of
social interaction?
proposer responder
1. Make an offer: 9:1 2. Conflict btwn emotion & cognition
(send emotional cue) ACC, Ins, dlPFC activation (interaction)
Reward anticipation
(NAcc) 3. Make a decision (reject: Ins)
4. Reward prediction
error
8

Previous studies:
emotion vs. cognition
Sanfey et al. Science, 2003 9

What are the neural mechanisms of human decision
making in the context of emotion and cognition?
dlPFC Anterior
insula
ACC
10

Time line for a single round of the Ultimatum Game
Subject decides
6 sec 6 sec 6 sec x sec 6 sec
+ He gets $9 Accept Reject He gets $0
You get $1 You get $0
Reveal Reveal Reveal Reveal Reveal
Fixation Partner Offer Options Outcome
x: Time continues until the subject decides. 11

Behavioral results from the Ultimatum Game
100
Schizophrenic
Control
80
Acceptance rates (%)
60
40
*
20
0
5:5 7:3 8:2 9:1
Offer
These are the offer acceptance rates averaged over all trials. Each of
schizophrenia patients and normal controls saw three $5:$5 offers, two $7:$3
offers, two $8:$2 offers, and three $9:$1 offers from human partners (10 offers in
total). 12

No difference between schizophrenia and controls was found in total earnings and
reaction times.
13

Group average of induced spectral power for all electrodes
schizo
Overall power is
decreased in schizo.
normal Especially when accepting
the offer -> fairness
valuation deficiency
14

Topography of event related spectral power for each condition
Schizo accept
Schizo reject
Normal accept
SD
Normal reject
-800~400ms -400~0ms 0~400ms 400~800ms 15

Group average of time series of event related spectral
power for all electrodes and each decision in gamma
schizo frequency range (30~50Hz)
Lower overall power in schizo.
Power change is not stable ->
meaning?? regional communication
is impaired.
normal
16

Phase synchronization analysis
Lachaux et al. 1999 17

Group average of phase synchrony for all electrodes
schizo
Long range
synchronization and
communication is
impaired in schizo
normal Especially when accepting
the offer -> fairness
valuation deficiency
18

Summary
• Is the Ultimatum game behavior of schizophrenia
different from that of normal controls?
– Yes. Abnormally accept.
– Fairness valuation deficiency? Or economically rational?
• Does time frequency analysis of EEGs show impaired
decision making in schizophrenia?
– Yes. Lower overall power amplitude.
– Especially when accepting the offer -> fairness valuation
deficiency
• Does phase synchronization of EEGs show impaired
decision making in schizophrenia?
– Yes. Lower phase synchrony.
– Especially when accepting the offer -> fairness valuation
deficiency
19

Acknowledgments
• Jaeseung Jeong, Ph.D.
– Advisor, Brain Dynamics Lab, KAIST,
• Dongil Chung
– Ph.D. candidate, Brain Dynamics Lab, KAIST
• Yang Tae Kim, M.D.
– Bugok National Hospital
20