Transcript Rowers high: behavioral synchrony is correlated with elevated pain

Rowers high: behavioral synchrony is
correlated with elevated pain threshold
Cohen, Ejsmond-Frey, Knight, & Dunbar (2010)
The role of endorphins
 Physical exercise
release of endorphins
 Psychological effects of endorphins?
 Release of endorphins
Physical Exercise
+
X?
Synchrony
social bonding
heightened social bonding
Rowers high
 Purpose: Will behavioral synchrony result in
elevated release of endorphins??
 Why rowers?
 Ergometeters (rowing machines)
Materials & Methods
 12 male athletes (M = 24.25, SD = 3.769)
 Two week testing period
 Within-subjects design: Individual vs. Group
 Medisave Littman Classic II sphygmomanometer
 Blood pressure cuff
 Measured before and after training
Results
 Endorphin hypothesis (general)
 Pain threshold increased following exercise
 Ruling out alternative explanations
 No differences in work effort
 No carry-over effects
Results
 Group pain threshold changes were significantly
elevated above those for individual trials
Discussion
 Synchronized activity heightens opioidergic
activity
 Other evidence – runners ‘high’
 Synchronous activities
 Wiltermuth & Heath, 2009
Old wives’ tales: the gossip hypothesis
and the reliability of cheap signals
Power (1998)
Dunbar’s ‘grooming and gossip’
hypothesis of language origins
 Vocal communication
 Adaptive response to increases in group size
 Replaced physical grooming
 More efficient
 Purpose: address problems with this theory
Coevolution of neocortex size,
group size, and language
 Cost of group living
 Reproductive suppression
 Coalitions serve as a buffer against costs
 The neocortex ratio
 Social grooming (Dunbar, 1991)
 Evolution of larger groups
 A feedback process
Vocal grooming:
the commitment problem
 Manual grooming: hard-to-fake currency
 Demonstrates commitment
 Cheney & Seyfarth (1990)
 Problems for vocal grooming hypothesis:
 Easy to fake
 Reduced commitment
 Does not produce natural opiates
Gossip: the reliability problem
 The ‘gossip’ hypothesis of language origins
 Rising group sizes
 Increased pressures on group cohesion
 New developments in vocal communication
 Problems for gossip hypothesis:
 Reliability
 Cheap signals
 Requires more energy expenditure
Contexts for gossip:
male and female reproductive strategies
Contexts for gossip:
male and female reproductive strategies
 Male vs. female philopatry
 Ancestral human societies have been viewed
as organized around male philopatry
 Evidence for female philopatry
 Modern societies (Dunbar & Spoors, 1995)
 Molecular genetics
Sexual signs and behavioral change
 Extracting energy from new sources
 Male investment
 Sexual signals
 Female signals elicit behavior change in males
 The material value of menstruation
Female coalitionary strategies:
proto-ritual
 Coalitionary strategies
 Manipulating menstrual signals
 Recruits male investment for female coaltions
 Sham menstruation (Power & Watts, 1996)
 Evolved into ritualistic displays involving:
 Red paint
 Song
 Dance
Menstrual ritual as
costly signal of commitment
 Cooperation vs. self-interest?
 Commitments
 Menstrual ritual: hard-to-fake
 Speech: easy-to-fake
Predictions from ‘sham menstruation’
model: archeological evidence
 Predicts increased male attraction to cosmetics
 Red pigment
 Evolution of ritual (Power & Watts, 1996)
 Increased stress on females
 Development of cosmetic rituals

More abundant use of iron ochre
 Archeological evidence supports these predictions
Evidence of ethnography: female
alliances, puberty rituals, and cosmetics
 Rituals associated with onset of menses
 1. Advertise prospective fertility in coalitional
contexts
 2. Menstruant participants as probationers until
initiated
 Traditional Cultures
 E.g., Venda of the Transvaal
Conclusion:
ritual and the gossip hypothesis
 Model: ritual as costly signaling of
commitment (hard-to-fake)
 Origins of ritual developed in collective manipulation
of menstrual signals
 Necessary for establishing ‘gossip’ as a basis of trust
 Menstrual ritual = Super grooming
 Conclusion: a necessary condition for the evolution
of language as gossip is the coevolution of ritual
Synchrony and ritual in the Andes
 Synchronized
opioidergic activity
 Social bonding
 Analgesia
 Rituals as a signal of commitment
 Social bonding