Rowers high: behavioral synchrony is correlated with elevated pain threshold

Cohen, Ejsmond-Frey, Knight, & Dunbar (2010)Rowers high: behavioral synchrony is correlated with elevated pain thresholdThe role of endorphinsPhysical exercise release of endorphins

Psychological effects of endorphins?

Release of endorphins social bonding

Physical Exercise+ X? heightened social bondingSynchronyRowers highPurpose: Will behavioral synchrony result in elevated release of endorphins??

Why rowers?

Ergometeters (rowing machines)

Materials & Methods12 male athletes (M = 24.25, SD = 3.769)

Two week testing period

Within-subjects design: Individual vs. Group

Medisave Littman Classic II sphygmomanometerBlood pressure cuffMeasured before and after trainingResultsEndorphin hypothesis (general)Pain threshold increased following exercise

Ruling out alternative explanationsNo differences in work effortNo carry-over effects

Results

Group pain threshold changes were significantly elevated above those for individual trialsDiscussionSynchronized activity heightens opioidergic activity

Other evidence runners high

Synchronous activities Wiltermuth & Heath, 2009

Power (1998)Old wives tales: the gossip hypothesis and the reliability of cheap signals

Dunbars grooming and gossip hypothesis of language originsVocal communicationAdaptive response to increases in group sizeReplaced physical groomingMore efficient

Purpose: address problems with this theory

Coevolution of neocortex size, group size, and languageCost of group livingReproductive suppression

Coalitions serve as a buffer against costsThe neocortex ratioSocial grooming (Dunbar, 1991)

Evolution of larger groupsA feedback process

Vocal grooming: the commitment problemManual grooming: hard-to-fake currencyDemonstrates commitmentCheney & Seyfarth (1990)

Problems for vocal grooming hypothesis:Easy to fakeReduced commitmentDoes not produce natural opiates

Gossip: the reliability problemThe gossip hypothesis of language originsRising group sizes Increased pressures on group cohesionNew developments in vocal communication

Problems for gossip hypothesis: ReliabilityCheap signalsRequires more energy expenditure

Contexts for gossip:male and female reproductive strategies

Contexts for gossip:male and female reproductive strategiesMale vs. female philopatry

Ancestral human societies have been viewed as organized around male philopatry

Evidence for female philopatryModern societies (Dunbar & Spoors, 1995)Molecular genetics

Sexual signs and behavioral changeExtracting energy from new sourcesMale investment

Sexual signalsFemale signals elicit behavior change in malesThe material value of menstruation

Female coalitionary strategies: proto-ritualCoalitionary strategiesManipulating menstrual signalsRecruits male investment for female coaltions

Sham menstruation (Power & Watts, 1996)Evolved into ritualistic displays involving:Red paintSongDance

Menstrual ritual as costly signal of commitmentCooperation vs. self-interest?

CommitmentsMenstrual ritual: hard-to-fakeSpeech: easy-to-fake

Predictions from sham menstruation model: archeological evidencePredicts increased male attraction to cosmeticsRed pigment

Evolution of ritual (Power & Watts, 1996)Increased stress on females Development of cosmetic rituals More abundant use of iron ochreArcheological evidence supports these predictions

Evidence of ethnography: female alliances, puberty rituals, and cosmeticsRituals associated with onset of menses1. Advertise prospective fertility in coalitional contexts2. Menstruant participants as probationers until initiated

Traditional CulturesE.g., Venda of the Transvaal

Conclusion: ritual and the gossip hypothesisModel: ritual as costly signaling of commitment (hard-to-fake)Origins of ritual developed in collective manipulation of menstrual signalsNecessary for establishing gossip as a basis of trustMenstrual ritual = Super grooming

Conclusion: a necessary condition for the evolution of language as gossip is the coevolution of ritualSynchrony and ritual in the AndesSynchronized opioidergic activitySocial bondingAnalgesia

Rituals as a signal of commitmentSocial bonding