The Evolution of the Social Mind

Robin Dunbar

Department of Experimental Psychology [email protected] Darwin’s Legacy

• Darwin’s main foci were speciation [Origin] and behaviour [Descent of Man and Emotions] • Behaviour was a central part of that engine [because it allows individuals to solve ecological problems more successfully] • The point of having a big brain is to allow more nuanced responses to ecological challenges A Core Philosophical Principle

Niko Tinbergen Tinbergen’s “Four Whys”: [1907-1988] Nobel Prize for Medicine 1973 • Mechanism [What?] = cognition, physiology, contextual cues • Function [Why?] = fitness consequences [always genetic fitness] • Ontogeny [How?] = development [genes vs learning] • Phylogeny [When?] = history [evolution meaning change]  Darwinian theory [“why”] provides the theoretical framework guiding and inspiring questions at the other levels AND the explanation for what we see  Understanding the mechanism [“what”] that brings about the function [“why”] may be as important as understanding the function itself Evolution of the Social Brain

• The Social Brain Hypothesis ….an explanation for why primates have unusually large brains

• Predicted group size for Monkeys

humans is ~150 Apes

“Dunbar’s Number” 10000

Human 1000 Social Groups Hunter- 100 Gatherer Societies These all have mean sizes of 10 100-200 1 Individual Tribes Neolithic villages 6500 BC 150-200 0 10 20 30 Modern armies (company) 180 Hutterite communities 107 Xmas Card Networks

‘Nebraska’ Amish parishes 113 10 business organisation <200 9 ideal church congregations <200 8 Domesday Book villages [1087 AD] 150 7 C18th English villages 160 6 GoreTex Inc’s structure 150 5 4

Research sub-disciplines 100-200 of Cases Number 3

2

Small world experiments 134 1 0 100-124125-149150-174175-199200-224225-249250-274275-299300-324325-349350-374 Hunter-Gatherer communities 148 0-24 25-49 50-74 75-99 Xmas card networks 154 Maximum Network Size How Many Facebook Friends?

• Two UK stratified 800 randomised samples 700 • Adult regular internet users 600 500

• N=3300 in total 400

• Mean age = 39 [18-65] Frequency 300 200

100 • Mean = 169.5 0 15 35 65 85 150 250 350 450 550 650 750 850+ Number of Friends

• Composite analysis of Stephenwolfram.com one million Facebook pages N  1 million Facebook pages

mode = 150-250 Why Your Network Matters

What best predicts your survival for the next 12 months after a heart attack?

Meta-analysis of 148 studies of heart attack patients BUT….our friends are NOT all the same!

Our social world is less like this

…..and more like this The Expanding Circles Intensity Our relationships form a hierarchically inclusive series of circles of increasing size but decreasing intensity EGO [ie quality of relationship] 5 15 Individual Contact Rates per Day 50

150 500 1500 The Divided Network

• The layers probably serve very different social FAMILY functions for us EGO • In addition, our personal 5 networks of ~150 actually FRIENDS consist of two quite separate 15 [BUT inter-digitated] networks 50 o typically a 50:50 split 150 • People who have big extended families have fewer friends Stable Family, Fragile Friends

We have to KIN work at friendships Women who but ‘kinships’ score high on come for neuroticism free scale list fewer Friends Family will female kin always Emotional Closeness support you come what Change over Time may 0 9 18 months How Primates Make Relationships

Primate social bonds seem to involve two distinct components:

 An emotionally intense component [=grooming]

 A cognitive component [=brain size + cognition = relationships of trust, obligation and reciprocity] The Limits to Intentionality...

A natural limit at 5th order intentionality:

“I intend that you believe that Fred understands that we want him to be willing to [do something]…” [level 5] Cognitive Limits to Sociality?

20

• Achievable intentionality level 10 indexed from stories

Frequency of failure of Frequency th • 5 order seems to be the limit 0 1st 2nd 3rd 4th 5th 6th 7th 8th 9th

Level of intensionality

 Intentionality correlates 30 with size of support clique [clique size = no. of core 20 intimate relationships]

Clique sizeClique 10 • High orders of mentalising are lost during clinical phases of: 0 o Bipolar disorder [Kerr, Dunbar, Bentall 2003] 0 2 4 6 8 10 o Paranoid schizophrenia [Swarbrick 2001] Level of intensionality Insights from Neuroimaging

Powell et al. (2010, 2012, 2014); Kanai et al. (2011); PLUS Sallet et al. (2013) in macaques • Neuroimaging reveals correlation between social network size and orbitofrontal PFC volume [and rest of ToM circuit] in humans AND macaques • In a fine-grained VBM (voxel) analysis: overlap of network size and intentional competence in the ventromedial PFC Why Time is Important Why Time is Important

50

• Grooming as the Predicted for Humans bonding agent in 40 primates • Grooming time is 30 determined by group size 20

Social Time (%)TimeSocial

• …with an upper limit 10 at about 20% of total daytime 0 0 20 40 60 80 100 120 140 160

Group Size How to Prevent Friendships Dying

Change in Emotional Closeness ♂ over 9 months ♂

♀

♀

LESS MORE LESS MORE change in activity score change in contact frequency How Grooming Works

50

Predicted for Humans 40

30

20

Social Time (%)TimeSocial

10

0 0 20 40 60 80 100 120 140 160

Group Size

• Light stroking triggers endorphins in the brain in primates • Endorphins are relaxing • They create a psycho-pharmacological environment for building trust Grooming in N=18 Humans

Nummenmaa et al. (2016) N=45

• PET study using carfentanil as opiate antagonist [particular affinity to μ-receptors for β-endorphins] using light stroking • Significant response in some key regions that suggest endorphin activation even to light touch Attachment Style Social Importance of Touch

Male Where touch Female is allowed depends on relationship quality

Correlation between allowable touch and status Suvilehto et al. (2015) Grooming Time in Humans?

50 • If we bonded our Predicted for Humans groups using the 40 standard primate

mechanism 30

….we would have to 20

spend 43%(%)TimeSocial of the day grooming 10

0 0 20 40 60 80 100 120 140 160

Group Size Grooming Time in Humans?

• In fact, we spend only 50

20% of our time in Predicted for Humans social interaction 40 …..from a sample of 7 societies from 30 Dundee to New Guinea 20

Social Time (%)TimeSocial

10 • How do we bond our

super-large 0 communities? 0 20 40 60 80 100 120 140 160 Group Size The Three Ways We Bridged the Gap Language and the rituals of religion

50

Modern humans 40 Archaic humans The

30 H. erectus Bonding Gap

20 Music/singing and dance

Australopiths Predicted Grooming (%) Time 10 -.5 0.0 .5 1.0 1.5 2.0 2.5 3.0 3.5

Millions Years BP Laughter a cross-cultural trait shared with chimpanzees Laughter Triggers an Endorphin Response

Laughter

2 4 T-score Comedy EdinburghEdinburgh FringeFringe

Endorphin receptors in brain Neutral 2 firing4 up during laughter T-score

Procedure: • pain test • video/activity Dunbar et al. (2012) • pain re-test Manninen et al. (subm) Change in Pain Threshold Something in the Way She Moves….?

A study carried out in Brazil

with very simple dance Threshold in Pain Change moves

Self-in-Other Index Index 12/3/2015 choir picture - Google Search

choir picture

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The Life of a Choir Kid | Let's win college. www.theprospect.net

The Icebreaker Effect Visit page View image

Related images:

• 4 singing classes vs 3 hobby Images may be subject to copyright. classes run by WEA

• Singing produces an immediate effect of bondedness

• …which https://www.google.co.uk/search?q=choir+picture&espv=2&biw=1440&bih=768&tbm=isch&imgil=GpWRr7uKYqpTGM%253A%253Bga-13AdbaS9bBM%… 1/11 continues

Pearce et al. (2015) Audience Response Change in pain threshold

to an Intensely • A very emotional film Emotional Film vs. Comparison to factual documentaries

• 237 in groups of 5-50

1. Does pain threshold [=endorphin activation] Change in bondedness increase after watching film ?

2. Does sense of belonging to group increase after watching film? Two more important mechanisms for social bonding….

Eating and alcohol are both extremely effective triggers of endorphin activation

You cant do any of these online! Number of friends you can Friends on Tap? count on

• National survey carried out for CAMRA by YouGov

• People who have a regular ‘local’: o are happier o are more satisfied with life o feel more engaged with their local Trust those around you community o Are more trusting of those around them o have more close friends o have longer conversations o drink less Why You Should Say “No” to the Sandwich on the Run?

• 2000 people sampled in UK for The Big Lunch • People who eat dinners socially are: o Happier o More trusting of others o More engaged with local community o More contented with life People who eat dinner with others more o …and more friends often each week have more intimate friends Never Rarely Occasionally Sometimes Often Frequency of social dinners Thanks ….!