Download Do you feel or reason?

Intuition and Deliberation
- Two Systems for Strategizing in the Brain
Duo-process theory distinguishes
between intuition and reasoning.
Intuition (system 1): fast and emotional
Reasoning (system 2): slow and controlled
These differences imply different
games might be fundamentally
different.
coordination games vs. dominance
solvable games
dominance solvable games
prisoner’s dilemma game
eliminate
Confess
Don’t
confess
Confess
2,2
4,0
Don’t
confess
0,4
3,3
iterated elimination of dominated
strategies
eliminate (first)
eliminate (second)
Confess
Don’t
confess
Confess
2,2
1,0
Don’t
confess
0,4
3,3
Games that can be solved by iterated
elimination is called dominance
solvable games.
Notice that computers can be very good at
dominance solvable games, maybe even
better than human.
Coordination games are very
different.
Meeting in NY game
Grand
Central
Empire
State
Grand
Central
1,1
0,0
Empire
State
0,0
1,1
There is nothing to eliminate.
Computers may be very bad at it but
human may be better.
Studies on coordination games are few.
Mehta et al (AER, 1994) asked subjects to
name one color, one number and one year.
•When subjects were not rewarded based on their
answers, they…
•When subjects were rewarded if they said the
same thing as their randomly assigned partners,
they…
•When subjects were not rewarded based on their
answers, blue and red turned out to be equally
popular (35% each), the most popular number was
7 (11%) and the current year was named 6.8% of
times.
•When subjects were rewarded if they said the
same thing as their randomly assigned partners,
58.9% people named red, 40% of people chose
number 1 and the 61.1% named the current year.
In Schelling’s terms, the color red, the
number 1 and the current year are focal
points.
•What exactly focal points are and how do people
reach a focal point partly motivate this study.
•We would like to study both the behavioral and
neural difference between dominance solvable and
coordination games.
Compare coordination games with
dominance solvable games:
There is nothing to eliminate.
Computers may be very bad at it but
human may be better.
Methodology: We scanned 21
subjects in an fMRI scanner when
they were making choices in
dominance solvable and coordination
games.
•We would like to know the natural reaction of
subjects so only subjects who have never taken
any game theory course were recruited.
•Moreover, no feedback was given inside the
scanner.
•21 is a good sample size.
Most importantly, the payoff matrix is hard to
grasp (we cannot do it without paper and pen and
it is not a good reason if equilibrium fails just
because people have difficulties in understanding
the payoff matrix rather than in figuring out an
equilibrium), so we use the following new design
of box games and number games.
2 treatments: box and number
2 conditions: domi and coor
The following are some sample screens that
subjects saw.
1 2 3
A
B
C
you：1R
other：1R 1U
1 2 3
A
B
C
you：other
other：you
You： 0 1 2 3
Other： 0 1 2 3
you：other + 1
other：you
You： 0 1 2 3
Other： 0 1 2 3
you：other
other：you
Let us now solve for the two sample dominance solvable games.
Thank god there is nothing to solve for coordination games.
you：one right
other：one right one up
0 1 2 3
0 1 2 3
0 1 2 3
0 1 2 3
0 1 2 3
0 1 2 3
0 1 2 3
0 1 2 3
you：other + 1
other：you
0 1 2 3
0 1 2 3
0 1 2 3
0 1 2 3
0 1 2 3
Some of our subjects do like this (go back and forth between
herself and the other).
The point is it is easier to do elimination by eyes for these games.
●
●
●
●
●
you：one right
other：one right one up
●
0 1 2 3
0 1 2 3
●
0 1 2 3
●
0 1 2 3
you：other + 1
other：you
●
0 1 2 3
●
0 1 2 3
Now let us go back to the sample coordination
games. See how the answers “pop out.”
Our fMRI subjects (21) respond by:
Our pilot subjects (41) respond by:
Domi
Coor
1
(1)
1
(3)
16(e)
(32)
2
(4)
(1)
3
(1)
18
(33)
(2)
(4)
Domi
Coor
0 1 2 3
1 1 1 18
(1 5 2 33
0 1 2 3
18 2 1 0 (e)
12 8 14 4)
According to Schelling, focal points “have
symbolic or connotative characteristics that
transcend the mathematical structure of the game.”
We have some interesting sample questions in this
respect.
You: 747 767 380 757
Other: 747 767 380 757
You: 911 228 921 124
Other: 911 228 921 124
1 2 3 4
A
B
C
D
experiment design and time line:
event related and self-paced
Coor
or
Domi
Coor
or
Domi
Coor
or
Domi
Now we know the games, we turn to the fMRI
(functional magnetic resonance imaging).
a scanner
a typical EPI image
When neurons fire, blood releases oxygen to them
at a greater rate than to inactive neurons. Since
oxyhemoglobin and deoxyhemoglobin have
different magnetic susceptibility, this magnetic
signal variation can be detected using an MRI
scanner.
Given many repetitions of a thought, action or
experience, statistical methods can be used to
determine the areas of the brains which have more
of this difference as a result, and therefore which
areas of brains are active during that thought,
action or experience.
MR signal (S)
active
resting
t
TE
excitation
reception
experiment parameters
Slice 25, FOV read 256, FOV Phase 100
Slice Thickness: 4mm
TR: 2000 ms
TE: 34 ms
Phase Oversampling: 38
Base Resolution: 64
Phase Resolution: 100
In a nutshell, we estimate a general linear
model.
Signal = bd[Domi]+bc[Coor]+bm[Motor]+ε
and we run t-tests on bd - bc and bc- bd.
First, let us look at our behavioral data.
expected payoff
avg. payoff
against mode
Domi
35.81 sec (15.98) 66.97% (21%)
79.26% (21%)
Coor
9.78 sec (2.90) 46.10% (18%)
69.92% (18%)
reaction time
1.0
expected payoffs
Average of participants'
0.8
0.6
0.4
0.2
0.0
Box-Game
Number-Game
Grand Total
Dominance Solvable
Coordination
70
Average response times (secs)
60
50
40
30
20
10
0
Box-Game
Number-Game
Grand Total
Dominance Solvable
Coordination
Two observations can be drawn from the
behavioral data.
•Humans are really different from
computers (esp in Coor games). If we test
whether subjects’ choices are random by
Pearson test, the p-value is 0.00 (0.00 for
Coor). So they are not choosing randomly.
Bootstrapping the distribution of expected
payoffs shows that the p-value of the
expected payoff of a randomizer is 0.00.
•They take longer time to make choices in
Domi games than in Coor games.
The difference in reaction time complicates
data analysis.
One can argue that the difference we see in
bd – bc and bc- bd results from the
difference in reaction time instead of the
difference in nature of these two types of
games.
To address this, we run three other
regressions. In one, the “task” regressor is
parametrically modulated by reaction time.
In another, reaction time is incorporated as
other regressors (which do not convolve
with HRF). In the third, we only model the
first 8 seconds of each trial.
These three regressions give very similar
results.
Let first review some basics about the brain.
Domi-Coor (bd- bc)
Coor-Domi (bc- bd)
In short, in Domi-Coor, we find activation
in fronto-parietal network (the middle
frontal gyrus, the inferior parietal lobule,
precuneus).
On the other hand, in Coor-Domi we
consistently find activation in insula and
ACC.
Domi-Coor
Coor-Domi
What exactly do these results mean?
Domi-Coor: working memory
Coor-Domi: salience detection
Domi-Coor
Fronto-parietal activation results when tasks
require attention, conscious perception, reasoning
and memorizing.
Domi-Coor
Previous literature:
fronto-parietal activity observed when contrasting
logical reasoning to tasks where reasoning is not
required,
when contrasting challenging reasoning tasks to
straightforward ones,
or when contrasting a meaningful middle game
position to a random game position.
Dominance solvable games may induce players to
go through steps of reasoning. In each step,
players may need to eliminate some choices and
memorize.
Domi-Coor
Verbally encode and hold the targets of both:
Inferior parietal lobule is implicated in verbal
memory storage.
Eliminating dominated strategies may engage the
central executive which is to manipulate the
contents of storage: Middle frontal gyrus is
thought to execute goal-directed operations.
Keeping track of which strategies are eliminated
may require generating and retrieving a mental
image: Precuneus may be related to memory
retrieval and imagery.
Domi-Coor
The greater fronto-parietal activation in
dominance solvable games is consistent with the
hypothesis that these areas assist in step-by-step
deliberative mental processes.
One anecdote is this. The parietal lobe of
Einstein’s brain was 15 percent larger than average.
Maybe that is why he is smart?
Coor-Domi
Insula: implicated in subjective pre-reflective and
reflective representations of ongoing changes in
internal bodily and feeling states.
Insula receives information from receptors in the
skin and in internal organs. If an animal is hot, it
seeks shade. If hungry, it looks for food. If hurt, it
licks the wound.
ACC: a conflict monitor when tasks require
attention, novel or open-ended responses or when
cognitive uncertainty exists.
Coor-Domi
Previous literature:
When participants contemplate cooperating
instead of competing with another person,
when they judge other persons to be trustworthy
instead of being untrustworthy,
or when they experience social emotions such
as empathy or love, insula and ACC activate.
These emotions might have evolved to ensure
quick responses to the factors arousing them in the
presence of many stimuli.
Coor-Domi
Many social interactions involve myriad stimuli
but demand immediate decisions.
Rapid processing and extraction of the most
salient aspects of complex situations is
characteristic of intuitive decision making.
Complex: multi-purpose, respond to many factors
and be flexible
Quick processing: extract the most salient feature
Coor-Domi
The insula and ACC seem to be part of a general
network contributing to a
quick and exible evaluation of complex multi
dimensional experiences.
In our experiment, deciding within the
context of a coordination game which Nash
equilibrium has the most salient
characteristics requires rapid processing of various
cultural connotations as
well as geometric symmetry, centrality or even
mathematical oddity.
Coor-Domi
The middle insula receives inputs regarding the
physiological condition of the body from the
posterior insula and integrates
this with salient environmental stimuli.
The posterior insula and the
SMA/CMA are shown to be responsive to changes
of many sensory modalities, whereas the anterior
insula and ACC are sensitive to novelty.
Coor-Domi
The key to coordination may be the ability to
make judgments of salience common to both. That
is, the participant must identify features which are
likely to be salient not only to herself but also to
the other.
The previous studies all point to a possible role of
insula and ACC in identifying salience and
provide support for the hypothesis that the higher
activation we observe is due to participants
extracting salient features in order to coordinate.
Coor-Domi
Post-scan interviews indicated that many used
intuitions or “gut feelings” to identify the focal
points of coordination games. They just know how
to choose in coordination games.
Maybe they get their gut feeling from Insula and
ACC?
Step
To solve a dominance solvable game requires a
well defined number of steps. The greater is the
number of steps, the more taxing might be the
mental processes.
Maybe the fronto-parietal activation in dominance
solvable games might correlate with the number of
steps?
NCI
For coordination games, NCI (normalized
coordination index) measures how well
coordination is achieved.
Choice
1
Choice
2
Choice1
Choice2
Choice
1
Choice
2
Group
A
10
0
5
5
10
0
Group
B
0
20
10
10
20
0
NCI
(1*0+0*1)*2=
0
(0.5*0.5+0.5*0.5)
*2=1
(1*1+0*0)*2=
2
0
1
2
NCI
A high NCI means a high coordination rate,
perhaps reflecting a strong gut feeling aroused by
an obvious focal point while a low NCI (close to 1)
means choice is close to random.
Maybe the activation in insula and ACC in
coordination games may correlate with the NCI?
Step and NCI
We divide 40 dominance solvable games into 20
hard and 20 easy games depending on the number
of steps and similarly divide 40 coordination
games into 20 highly focal games and 20 less focal
games.
We build a second model where the two kinds of
games are modulated by the categories
respectively or
Signal = bd[Domi] bdStep[Domi Hard or
Easy]+bc[Coor]+bcFocal[Coor Focal or Less Focal]
+bm[Motor]+ε.
Step and NCI
Precuneus activates more in hard domi than in easy domi.
Precuneus plays a role in memory retrieval. The higher demand
for memory imagery and retrieval in hard dominance solvable
games may explain this activation.
Insula activates more in highly focal coor than in less focal coor.
The participants may have felt quite strongly that the other must
notice the same salient feature. This may be why insula
activation is higher for games which are more focal.
Payoff
A difficult game may generate a lower reward and different
participants may disagree about which games are difficult.
We build still another model where each task is modulated by its
grades,
Signal = bd[Domi] +bdgrade[DomigGrade]
bc[Coor]+bcgrade[CoorGrade] +bm[Motor]+ε.
Payoff
Precuneus activation is negatively correlated with domi grades of
a subject. Domi games with lower payoffs present harder
mental challenges.
Insula activation is positively correlated with coor grades of a
subject. Coor games with higher payoffs arouse the gut feeling
stronger.
Step, NCI, Payoff
The second and the third model suggest that the
more “effortful” mental process activated by
dominance solvable games are more heavily taxed
when the games are hard to solve, while the more
“effortless” mental processes activated by
coordination games are more strongly activated
when coordination is easy.
This provides additional support for the main
hypothesis of our research, that is, dominance
solvable games and coordination games set off
two quite different mental processes.
The big question is, if we know that there are two
very different networks that are activated when
people play Domi or Coor games, can we apply
what we have learned here to predict behaviors in
other games?
For instance, in trust games, do people reason or
rely on intuition? Can we infer from the brain
activations to make an educated guess at what they
will do?
Can we categorize players when they play an
interesting game (like p-beauty contest) by their
brain data so that we know whether they are using
a more calculating way or a more intuitive way to
reach their choices?
Hope you find the talk interesting.