Is it an error to be ‘too different’!? Neurobiology of social conformity Ale Smidts a Co-authors: Vasily Klucharev ab Kaisa Hytönen ab, Mark Rijpkema b.

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).