A challenge

A Challenge

• A Challenge

• SCN has become one of the big stories in neuropsychology and neuroimaging

• But what exactly is the nature of sociality in this context?

• The Challenge: Have we focussed on the right indices of sociality?

An explanation

• An explanation

• for the

• evolution of

• unusually large

• brains in primates

• Evidence:

• Group size is

• a function of

• neocortex volume

• in three different datasets

Predicted group size for humans is ~150

• Predicted group size for humans is ~150

• [Dunbar’s Number]

All these have mean sizes of

• All these have mean sizes of
• 100-200
• Neolithic villages 6500 BC 150-200
• Modern armies (company) 180
• Hutterite communities 107
• ‘Nebraska’ Amish parishes 113
• business organisation <200
• ideal church congregations <200
• Domesday Book villages 150
• C18th English villages 160
• GoreTex Inc’s structure 150
• Research sub-disciplines 100-200
• Small world experiments 134
• Hunter-Gatherer communities 148
• Xmas card networks 154

These all have mean sizes of

• These all have mean sizes of
• 100-200
• Neolithic villages 6500 BC 150-200
• Modern armies (company) 180
• Hutterite communities 107
• ‘Nebraska’ Amish parishes 113
• business organisation <200
• ideal church congregations <200
• Doomsday Book villages 150
• C18th English villages 160
• GoreTex Inc’s structure 150
• Research sub-disciplines 100-200
• Small world experiments 134
• Hunter-Gatherer communities 148
• Xmas card networks 154

Primate societies are hierarchically embedded

• Primate societies are hierarchically embedded

• As neocortex size increases, groups become socially more fragmented (grooming cliques get smaller)

• Somehow, they manage to balance a two-tier system

Bonding is a dual-process mechanism

• Bonding is a dual-process mechanism

• An emotionally intense component
• [= endorphins via grooming]
• A cognitive component
• [= cognition  brain size]

A natural limit at 5th order 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]

Intentional competence correlates with social network size

• Intentional competence correlates with social network size

• …..Does the hardware correlate too?

In a stereological analysis of gross volume: best predictor of BOTH intentional competence and network size is orbitofrontal PFC volume

• In a stereological analysis of gross volume: best predictor of BOTH intentional competence and network size is orbitofrontal PFC volume

• In a fine-grained VBM (voxel) analysis: overlap of network size and intentional competence in the ventromedial PFC

There is a clear causal sequence:

• There is a clear causal sequence:

• hardware  cognition [software]  behaviour

Grooming as the bonding agent in primates

• Grooming as the bonding agent in primates

• Grooming time is determined by group size

• …with an upper limit at about 20% of total daytime

If we bonded our groups using the standard primate mechanism

• If we bonded our groups using the standard primate mechanism

• ….we would have to spend 43% of the day grooming

In fact, we spend only 20% of our time in social interaction

• In fact, we spend only 20% of our time in social interaction

• …..from a sample of 7 societies from Dundee to New Guinea

• How do we bond our super-large communities?

endorphins are relaxing

• endorphins are relaxing

• They create a psycho-pharmacological environment for building trust?

Preliminary results from a first PET study (at Turku, Finland)

• Preliminary results from a first PET study (at Turku, Finland)

• Carfentanil as opiate antagonist with particular affinity to μ-receptors [for β-endorphins]

• Significant response in some key regions that suggest endorphin activation even to light touch

• Probably exploiting the same c-afferent fibre system as found widely in mammals [responds ONLY to light touch as in stroking movements of grooming]

Comparative brains:

• Comparative brains:

• Dr Susanne Shultz

• Dr Boguslaw Pawlowski

• Social Networks and Bonding:

• Dr Sam Roberts

• Dr Russell Hill

• Prof Alex Bentley

• Dr Wei Zhou

• Prof Didier Sornette

• Dr Emma Cohen

• Dr Anna Machin

• Imaging:

• Amy Birch

• Rachel Browne

• Dr Penny Lewis

• Dr Joanne Powell

• Dr Marta García-Fiñana

• Prof Neil Roberts

• Dr Lauri Numennmaa