The Secret Of Our Success - LSE Home

STICERD Morishima public lectureThe Secret of Our SuccessProfessor Joseph HenrichProfessor in the Department of Human Evolutionary Biology, Harvard UniversityHolder of Canada Research Chair at UBCProfessor Timothy BesleySchool Professor of Economics and Political ScienceW. Arthur Lewis Professor of Development Economics, LSEChairHashtag for Twitter users: #LSEHenrich

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A arly human migrations#cite note-9 Immense diversity of habitats Few environment-specific genetic adaptations How did we do it?3

Lost European Explorers Burke & WillsExpedition Trapped along CoopersCreek Couldn’t fish or hunt Able to survive on fishfrom locals, and nardoo Observed localsprocessing an aquaticfern. Bread Nardoo: indigestible &1860 CEtoxic. Thiaminase B1depletionAboriginal Processing Grind, leach, heatand use mussel shellspoon Grind, leach, bake inash

It’s not our intelligence Burke and Wills could not survive ashunter-gatherers– Aboriginals survived in Australiafor 60K as hunter-gatherers– No modules fired up, no instinctskicked in, and no generalintelligence bailed them out.– Couldn’t find water or identifyedible plants– Couldn’t hunt effectively, maketraps, spears or fishing hooks– Any local adolescent can do all ofthese things. What was missing?Brain680g5

Relativesuccess ofhumans notexplained by“intelligence”relative toother apesAlsoWorking MemoryStrategic thinkingWe humans get muchsmarter from 2.5 to25. Apes do not6

Wait, why do we seem so smart? We culturally inherit cognitive solutionsto many problems (it’s the software, notthe hardware) Tools—we socially learn affordances(screws, springs, levers, pulleys, etc.)– Wheel concept– Elastically stored energy– Compressed air Numbers systems Spatial cognition—3 coordinate systems Words—70,000 words in yourvocabulary (other languages 3-5000)Oksapmin count to 27How“smart”?7

The secret of our success It’s not our intelligence. Culture: we depend on cumulative bodies of culturalinformation—cultural adaptations.– High fidelity cultural transmission—good copiers– Sociality Collective Brains: innovation and accumulation is sociocultural process.– Larger, more interconnected populations generatemore complex tools, more sophisticated technologiesand larger toolkits Cultural Brain Hypothesis—cultural evolution drove(and drives) genetic evolution8

How might natural selection have shaped ourcognition to best exploit the socially-availableinformationPsychological Mechanism ofCultural LearningFormallymodeled Suppose you enter a novel environment(young or migrant). How do you figure out what to eat? Individual learning—costly Cultural learning Focus on food choices of older,healthy, and successful people.Logic ofNatural Selection9

How might natural selection have shaped ourcognition to best exploit the socially- availableinformationPsychological Mechanism ofCultural Learning Model-based mechanisms: from whomto learn? Content-based mechanisms Food, fire, artifactsFormallymodeled Norms, social groups Living kinds (danger info)Logic ofNatural Selection10

Model-based Selective Cultural Learning What cues should learners use to assess who in ismost likely to possess information useful/adaptive tothe learner.Aggregate to select preferredmodels– Skill/competence– Success– Prestige (cues of attention, deference)– Health (positive affect)– Age—older children and older people– Self-similarity: sex and ethnicity/dialect11

Evidence for model-based cultural learning Substantial experimental evidencethat children and adults use thesecues (and some infant work).– Skill, competence, reliability– Success– Age, health and affect– Sex, ethnicity (dialect)– Prestige-use other’s opinions toguide attention and learning Attention Sociolinguistic cues Ethology (body posture)Vast array of domains: Food preferences Mate choice Technological adoptions Word meaning, dialect Economic strategies Suicide Beliefs (e.g., invisible agents) Cognitive strategies Reputational content Social motivations (fairness& punishment )Reliably develops relatively early, occurs automaticallyand often remains unconscious. Increases underincentives.12

Cultural Adaptations: If individuals learning from the most successful &healthy (etc.), then over generations populations can converge on locally adaptiverepertoiresPsychological Mechanism ofCultural LearningSocial Process LearningPopulationProcessFormallymodeledLogic ofNatural SelectionCulturalAdaptationsProductsCultural ProductsTools, technologiesDietary repertoiresFood processingtechniquesRitual practicesEcological knowledgeMedical knowledgeCommunicativesystemsPermits theorizing of(1) Sociality effects(2) Adaptive lags(3) Maladaptations13

Cultural Adaptations Cultural evolution often operates outside of conscious awarenessCultural adaptations emerge withoutactors’ understanding causality or costsand benefitsAppear “rational” (appear “designed”)Procedures and subgoals are transmitted.Causal understandings are often backedout, post-hoc– Boomerangs, many medicinesSometimes causal understandings arewrong.Sometimes NOT understanding thecausality is crucialSpicesNixtamalization14

Genetic EvolutionNatural SelectionPsychologicalcapacities forculturallearningOtherEvolvedAspects ofPsychologyCulturalevolutionarypsychologyComplex Practices Social NormsRitualsInstitutionsToolsCultural Adaptations(Cultural Products)Cultural Psychologies15

Point“Natural selection is the only known causal process capable of producingcomplex functional organic mechanisms”(Buss, Haselton, Shackelford, et al. 1998) Nope Cultural evolution, driven by unconscious selective attention, canalso generate complex function units that appear designed to solvespecific problems.– Spice tastes and recipes– Nardoo– Alkali in corn– Writing systems (Reading changes our brains) Also, natural selection can act on cultural variation.16

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Culturally-evolved cognitive adaptations Numerals & spatial reference systems These mental abilities evolved culturally to fit our innatepsychology.Mental abacus—extraordinarycomputation abilities– Real abacus—harnesses visiospatial abilities, object tracking &grouping abilities.Languages evolved culturally to “fit”our brains, and to be easily learnableby children18

The CollectiveBrainChapter 12, Secret of Our Success19

Population Size and Tool Complexity 10 societies, Oceania (eHRAF)Need a naturalexperiment:Does populationpredict the size andcomplexity of toolkits?Marine foraging toolcomplexityKline and Boyd 2010 Proc-b

Technological variety and complexityß 0.805p 0.005ß 0.706p 0.022Cognitively lesssophisticated?Log ScaleLarger islands had larger populations, more tools, and greater toolcomplexity. This all occurred in a few thousand years. Stands up tomany control variables (ecological variables).

Australian Aboriginal Stone tools(circa 1700)Upper Paleolithic tools (35K)?Mousterian (Neanderthals)Oldowan 1.8 myaTTasmanian Tools(circa 1700)22

Europeans 1642 Hunter-gathererbands 4000 Tasmanianson an island 2/3rdthe size of Ireland Simplesttechnology of anypeople everencounteredWallabySkin(one piece)23

Archaeology deepens the puzzle In last 10,000 years, Tasmanians lost or never evolved a series of valuable skills and technologies.Bone tools, fishing, cold-weather clothing, hafted tools, nets,fishing spears, barbed spears, spear-thrower, durablewatercraft, and boomerangs.Dressed in one-piece wallaby skins, used 1-piece spears andclubs for hunting. Drank from skulls.In all, the Tasmanian toolkit consisted of only about 24 items.Tasmania watercraft (no paddles)Drinkingvessel24

The control group Across the Bass Strait, the Victorian aborigines possessed almost the entireTasmanian toolkit plus hundreds ofadditional specialized toolsincluding Multi-pronged fishing spears, spearthrowers, boomerangs, mountedadzes, composite tools, a variety ofnets for birds, fish and wallabies,sewn bark canoes, string bags, groundedge axes and wooden bowls fordrinkingWhy would they lose such useful pieces of technology?25

Collective Brains Can Shrink Rising seas cut Tasmania off This drastically reduced the effective size of the social network for culturallearningGradually, over 1000’s of years, usefultechnologies and knowledge ebbedaway.This did not happen in Victoria, as theywere connected with larger networks ofAustralia.Point: cultural evolution is a socialprocess that depends on the size ofinterconnected population at somelevel, the size of the continent.Innate differences unlikely.Polar Inuit26

250Tasmanians200Region 0-1-1.2 -1.4 -1.6 -1.8 -2-2.2 -2.4 -2.6 -2.8 -3α/β (modal effect inference over spread)Cultural transmission may create cumulative adaptation,but only if the pool of potential cultural models is sufficiently large(sudden drops in population size may initiate adaptive losses-3.2

To the laboratory . Field evidence is provocative, but can we demonstrate this in the lab, in a controlled setting?Micro-societies over success laboratory generations 2 experiments Start with naïve,unskilled: will greatersociality cause skill toaccumulate? (n 100) Start with experts: willgreater sociality inhibitloss of skill overgenerations? (n 100)k 1k 5Collab: Michael Muthukrishna28

Experiment 1: UnskilledGeneration 1 Goal: replicate target image using complex image editingprogramTime limitPaid for own and student’sperformance.Access 1 or 5 modelsAfter task: can write up to 2pages for “student”Target Image Next generation gets the (1) model’s product, (2) write-up and (3) target imageSkill similarity to target image29

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The dataIn Generation 10Everyone in 5-Modeltreatment is more skilledthan everyone in 1-Modeltreatment.31

More sociality slows decay rate and raisesequilibrium skill levelDemonstrates the Tasmanian-like EffectDifference inequilibriumskillsNot “intelligence”Not incentivesJust sociality32

Tools and rules for communication Languages are products of cultural evolution, sets of tools and rules.– Adaptations for communication Sign, whistle and hum languages Warmer climates have moresonorous languagesErgo, the same predictions apply– Larger speaker communities have More words—gain and loss inPolynesia. More phonemes Informationally more efficient33

Sound (phonemes) InventoriesQuentin Atkinson50 language familiesPhonemes vary from 11 to 140across languagesMore phonemes shorter wordsWEIRDist Language: English(most words, high IE, morpho-simple)Hay andBauer 200734

The Cultural BrainHypothesis Constant pressure for larger brains that arebetter able to acquire,store, organize andretransmit cultural info.As soon as brainsimprove, increasing insize, cultural evolutionrapidly expands the poolof information.Genetic Ancestral rBrainsTrackingFoodprocessingEvenlargerbrainsHits thingMedplantsFancytoolsDiv of info35

Recurrent features ofancestral selectiveenvironments createdby cultural evolutionPsychologicalmechanisms ofcultural learningCult. Evol.Fire, CookingFolkbiologicalknowledgeHierarchical taxCat.-based induct.Essentialism, sel. att.Tax. inheritanceTracking, watercontainersRunning adaptationsSpringy arches, sweatArtifactsTool/ weaponsArtifact cognitionFunctional stanceOverimitationTap unevendistrib of skillLogic ofNatural SelectionShort colons, stomach,etc. Interest in fireNormsInstitutionsEthnicgroupsPrestige status & ethologyTwo pridesNorms psychologyOntology social rulesProsocialityEthnic categorizationInferencePreferential interaction36

Cultural Brain HypothesisPredicts our specializations &oddities Explains rapid expansion of ourbrains, and large size. Account for many features ofhuman anatomy/psychology Cognitive differences betweenspecies Cultural learning, overimitation Extended childhoods Menopause37

Big Picture What kind of animal? Important question Effects institutional and policy design.All social/behaviorsciences implicit assumeanswers.A cultural species,produced by culture-drivengenetic evolution38