1. 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),
a – Rotterdam School of Management, Erasmus University
b – Donders Institute for Brain, Cognition and Behaviour, Nijmegen
21-23 August Summer Workshop on Decision Science, U of Michigan

3. 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

4. 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%

5. Groningen,

7. Solomon Asch found that the (genuine) participants conformed on 32% of the trials and only 26% of people never conformed (1951).

8. 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

9. Error Related Negativity

11. Error Related Negativity predicts learning
Subjects played a competitive, zero-sum game called “matching pennies”
Human ERP responses closely resemble model outputs. a, Prediction errors generated by the reinforcement model parallel human ERP responses. The prediction errors of the model (right) paralleled the feedback-locked ERP responses of humans (left). ERP data are z-transformed for ease in comparison with model output. PE, Prediction error.
Cohen & Ranganath, J. Neurosci. 2007;27:

12. NAc involvement in reward prediction error
2002

13. 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.
Fields et al 2007

14. 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

15. Normative rating + Face (S2)
2 sec
fMRI session
Attractiveness rating
Normative rating + Face (S2)
2 sec
Face (S1)
2 sec
conflict
Response OR OR
conflict no
conflict
Behavioural
session

16. 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

17. Normative rating + Face (S2)
2 sec
fMRI session
Attractiveness rating
Normative rating + Face (S2)
2 sec
“positive”
conflict
Social conflict effects: confirmatory [no conflict] vs. conflicting group feedback
Conformity effect: subsequently changed vs. unchanged ratings of attractiveness due to group feedback OR OR
“negative”
conflict no
conflict
BOLD

18. Behavioral Effects: Changes of attractiveness ratings induced by group ratings
Changes of attractiveness = relative changes of attractiveness in 2nd (bechaviural0 session

19. ROI-analysis

24. Individual differences in conformity & NAc activity

25. Social vs. Non-social Control
(Behavioral study, N = 62)

26. fMRI contrast: Social vs. Non-social Control
Conformity
Social conflict

28. Summary I
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
To sum up, our results indicate that a deviation from social norms triggers an error related response in para-cingulate region in part predicting the conformity. Subsequent conformity is forecasted by activation of brain regions consistently involved in processing of punishment and by the inactivation of regions involved in processing of rewards.

29. 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

30. 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

31. Does a temporal inhibition of the RCZ
affect subjects’ conformal behavior?

32. Design & Procedure
Continuous Theta Burst Stimulation paradigm (cTBS) - a 40 s train of uninterrupted TBS is given (600 pulses) (Huang et al., 2005)
TBS- Low-intensity burst of rTMS at 50 Hz.
Off-line
cTBS
40 sec

33. 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)

34. 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.

35. 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

36. 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

37. Questions & Discussion
Interested in post-doc?
(C) Erasmus Centre for Neuroeconomics (
& Donders Institute for Brain, Cognition and Behaviour

38. Further reading
Klucharev et al. (2009), “Reinforcement signal predicts social conformity”, Neuron, 61,
Klucharev, Smidts and Fernandez (2008), “Brain mechanisms of persuasion: How ‘expert power’ modulates memory and attitudes”, Social Cognitive and Affective Neuroscience (SCAN), 3(4),
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).