Cohen, Ejsmond-Frey, Knight, & Dunbar (2010) Rowers high:
behavioral synchrony is correlated with elevated pain
threshold
Slide 2
The role of endorphins Physical exercise release of endorphins
Psychological effects of endorphins? Release of endorphins social
bonding Physical Exercise + X? heightened social bonding
Synchrony
Slide 3
Rowers high Purpose: Will behavioral synchrony result in
elevated release of endorphins?? Why rowers? Ergometeters (rowing
machines)
Slide 4
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
Slide 5
Results Endorphin hypothesis (general) Pain threshold increased
following exercise Ruling out alternative explanations No
differences in work effort No carry-over effects
Slide 6
Results Group pain threshold changes were significantly
elevated above those for individual trials
Slide 7
Discussion Synchronized activity heightens opioidergic activity
Other evidence runners high Synchronous activities Wiltermuth &
Heath, 2009
Slide 8
Power (1998) Old wives tales: the gossip hypothesis and the
reliability of cheap signals
Slide 9
Dunbars 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
Slide 10
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
Slide 11
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
Slide 12
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
Slide 13
Contexts for gossip: male and female reproductive
strategies
Slide 14
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
Slide 15
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
Slide 16
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
Slide 17
Menstrual ritual as costly signal of commitment Cooperation vs.
self-interest? Commitments Menstrual ritual: hard-to-fake Speech:
easy-to-fake
Slide 18
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
Slide 19
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
Slide 20
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
Slide 21
Synchrony and ritual in the Andes Synchronized opioidergic
activity Social bonding Analgesia Rituals as a signal of commitment
Social bonding
