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 and Guillen Fernandez b Published in Neuron (2009), a – Rotterdam School of Management, Erasmus University b – Donders Institute for Brain, Cognition and Behaviour, Nijmegen 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%

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:

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 conflict no conflict fMRI session Face (S1) 2 sec Response Behavioural session

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 “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-line cTBS 40 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? (C) Erasmus Centre for Neuroeconomics ( & Donders Institute for Brain, Cognition and Behaviour

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).