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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 social bonding Physical Exercise + X? heightened social bonding Synchrony
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 • 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