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Is it an error to be ‘too different’!? Neurobiology of social conformity
Ale Smidtsa
Co-authors: Vasily Klucharevab Kaisa Hytönenab, Mark Rijpkemab and Guillen Fernandezb
Published in Neuron (2009), 140-151
a – Rotterdam School of Management, Erasmus University b – Donders Institute for Brain, Cognition and Behaviour, Nijmegen
21-23 August 2009 Summer Workshop on Decision Science, U of Michigan
Social norms
• Injunctive norm – perception of common (dis)approval of a particular kind of behavior. – What you should do
• Descriptive norm – particular behavior that is most common in a given situation
– What people actually do
Sheer information on others’ behavior can be very influencing
Re-use of towels in hotel rooms (field experiment; Goldstein and Cialdini, 2007)
• ‘Help save the environment’ 34%
• ‘75% of guests who stayed in this room
used their towel more than once’ 49%
33
69
0
10
20
30
40
50
60
70
% littering N = 77/77 P < 0.001
nongraffitigraffiti
13
27
0
5
10
15
20
25
30
% stealing N = 71/60 P = 0.035
nongraffiti
graffiti
Solomon Asch found that the (genuine) participants conformed on 32% of the trials and only 26% of people never conformed (1951).
Hypothesis:
•A deviation from group’ behavior (i.e. a conflict with group norms) evokes activity similar to Error Related Activity in reinforcement learning.
Main areas involved:
-dorsal cingular cortex (RCZ)
-nucleus accumbens (NAc)
-midbrain
Error Related Negativity
Error Related Negativity predicts learning
Cohen & Ranganath, J. Neurosci. 2007;27:371-378
2002
NAc involvement in reward prediction error
Fields et al 2007
Dopamine response = Reward occurred – Reward predicted
Prediction error – the discrepancy between an actually received reward and its prediction.
Learning is proportional to the prediction error.
Experimental Questions:
• Does the ‘conflict with the group’ (i.e. conflict with the group norms) evoke activity similar to Error Related Activity in dorsal cingular cortex (RCZ) and nucleus accumbens (NAc)?
• Does Error Related Activity correlate with conformity (= behavioural change in the direction of the group)?
Error threshold
Error response
Face (S1)2 sec
Attractiveness rating
Normative rating + Face (S2)2 sec
OR
OR
conflict
conflict
no conflict
fMRI session
Face (S1)2 sec
Response
Behaviouralsession
Experimental Procedure
Participants: 25 females (age: 18-22; two subjects were excluded due to motion artifacts, one as misbelieving the cover story).
fMRI session (1.5T Sonata, Siemens):
• Task: rating the physical attractiveness of faces (in total 222 faces)
• Normative Group Ratings: rating of the face by average European female from Paris and Milan.
Behavioral session (30 min later outside the scanner):
• Task: rate again the 222 faces
Face (S1)2 sec
Attractiveness rating
Normative rating + Face (S2)2 sec
OR
OR
“negative” conflict
“positive” conflict
no conflict
fMRI session
BOLD
Social conflict effects: confirmatory [no conflict] vs. conflicting group feedback
Conformity effect: subsequently changed vs. unchanged ratings of attractiveness due to group feedback
Behavioral Effects: Changes of attractiveness
ratings induced by group ratings
ROI-analysis
Individual differences in conformity & NAc activity
Social vs. Non-social Control (Behavioral study, N = 62)
fMRI contrast: Social vs. Non-social Control
Social conflict Conformity
the conflict with the group evokes error-activity at
rostral cingulate zone (RCZ) and nucleus
accumbens (NAc)
the conformity (i.e. the change of judgment due to
group feedback) is correlated with the activation of
the RCZ, and by the inactivation of NAc
Summary I
Summary II
deviation from social norms triggers an immediate neural error response
social conformity complies with the principles of the reinforcement learning
individual differences in conformity could be based on a variable reward prediction error signal
fMRI only correlational: What about causality?
• Follow-up study (in progress):
rTMS modulation of social conformity
Vasily Klucharev, Moniek Munneke, Ale Smidts and
Guillen Fernández
Does a temporal inhibition of the RCZ affect subjects’ conformal behavior?
Design & Procedure
• Continuous Theta Burst Stimulation paradigm (cTBS) - a 40 s train of uninterrupted TBS is given (600 pulses) (Huang et al., 2005)
Off-linecTBS40 sec
Design & Subjects
Total 90 subjects (aged 19–27 years, all females) :
• 30 subjects: cTBS of RCZ
• 30 subjects: cTBS of the precuneus region
• 30 subjects: sham control (no TMS)
The TMS intensity – 80% of Active motor threshold (‘foot twitching’)
MANOVA (Social conflict – 3 levels as within-subject factor, TMS location/type – two/three levels as between-subjects factor)
How the outcomes are informative for the central issue:
• Results will demonstrate that a temporal inhibition of the RCZ affects subjects’ conformal behavior.
• Results will show that social conformity complies with the principles of the reinforcement learning.
Social Norms campaigns
• High chance of success because it relies on a basic principle
• But, precisely because of that: carefully craft the message to prevent boomerang effects
Effect of descriptive norm information on energy use
Schultz et al., Psych Science (2007), Field experiment
• Households received info on their own and on the average energy use in their neighborhood
– HHs consuming more than average, decreased their energy use
– HHs consuming less than average, increased their energy use
Questions & Discussion
Interested in post-doc? [email protected]
(C) Erasmus Centre for Neuroeconomics (www.erim.nl/neuroeconomics/)
& Donders Institute for Brain, Cognition and Behaviour
Further reading
• Klucharev et al. (2009), “Reinforcement signal predicts social conformity”, Neuron, 61, 140-151.
• Klucharev, Smidts and Fernandez (2008), “Brain mechanisms of persuasion: How ‘expert power’ modulates memory and attitudes”, Social Cognitive and Affective Neuroscience (SCAN), 3(4), 353-366.
• Stallen et al. (2009), “Celebrities and shoes on the female brain: The neural correlates of product evaluation in the context of fame”, Journal of Economic Psychology (forthcoming).
