Brain & BehaviorBrain & BehaviorPsych 545Psych 545

Dr David A KaiserDr David A Kaiser

Office: Bldg 6 – A116 x6773 Office: Bldg 6 – A116 x6773 dakaiser@mail.rit.edudakaiser@mail.rit.edu

www.rit.edu/~dakgshwww.rit.edu/~dakgsh

Largest Brain on planet, 9.2 Largest Brain on planet, 9.2 kgkg

Belongs to Sperm WhaleBelongs to Sperm Whale

Absolute Brain Weight – Absolute Brain Weight – Does it reflect intelligence? Does it reflect intelligence?

SpeciesSpecies Adult Brain Adult Brain Weight Weight (grams)(grams)

ChimpanzeChimpanzeee

450450

HumanHuman 1,3501,350

Bottlenosed Bottlenosed dolphindolphin

1,600 1,600

African African elephantelephant

6,0756,075

Fin whaleFin whale 7,2007,200

Sperm Sperm WhaleWhale

9,2009,200

Relative Brain WeightRelative Brain Weight

SpeciesSpecies Brain to Body Brain to Body WeightWeight

HumanHuman 2.1 %2.1 %

Bottlenosed Bottlenosed dolphindolphin

1.2 % 1.2 %

ChimpanzeeChimpanzee .7 %.7 %

African elephantAfrican elephant .5 %.5 %

Killer whaleKiller whale .1 %.1 %

CowCow .08 %.08 %

Sperm WhaleSperm Whale .02 %.02 %

EncephalizationEncephalization

• Increase in brain size during Increase in brain size during evolution of SPECIES, with no evolution of SPECIES, with no concomitant increase in body sizeconcomitant increase in body size

• ““Of all animals, man has the largest Of all animals, man has the largest brain in proportion to his size” - brain in proportion to his size” - AristotleAristotle

EncephalizationEncephalization

Encephalization Quotient (EQ)Encephalization Quotient (EQ)

• Anatomical estimate of species’ intelligence (non-Anatomical estimate of species’ intelligence (non-behavioral)behavioral)

• EQ = ratio of brain weight of animal to brain weight of EQ = ratio of brain weight of animal to brain weight of “typical” animal of same body weight (Jerison, 1973)“typical” animal of same body weight (Jerison, 1973)

• EQ represents index of residual value of brain massEQ represents index of residual value of brain mass

• Total Brain Mass = Brain for body size Total Brain Mass = Brain for body size + Residual brain for higher + Residual brain for higher functionsfunctions

Encephalization Quotient (EQ)Encephalization Quotient (EQ)

???????? 9.0

Human 7.4

Dolphin 5.6

Killer whale 2.9

Chimpanzee 2.5

Rhesus Monkey 2.1

Elephant 1.9

Whale 1.8

Dog 1.2

Cat 1.0

Horse 0.9

Sheep 0.8

Mouse 0.5

Rabbit 0.4

Encephalization Quotient (EQ)Encephalization Quotient (EQ)

          1 g brain for hummingbird

Hummingbird 9.0

Human 7.4

Dolphin 5.6

Killer whale 2.9

Chimpanzee 2.5

Rhesus Monkey 2.1

Elephant 1.9

Whale 1.8

Dog 1.2

Cat 1.0

Horse 0.9

Sheep 0.8

Mouse 0.5

Rabbit 0.4

EQ through evolutionary EQ through evolutionary timetime

• Are we evolving into smarter and Are we evolving into smarter and smarter creatures? Or was humanity smarter creatures? Or was humanity a fluke?a fluke?

• In other words, was there a neural In other words, was there a neural arms race in the past or an unusual arms race in the past or an unusual mutation process in one line of mutation process in one line of primates?primates?

Evolution of behavioral complexityEvolution of behavioral complexity

Neural arms race in mammalian group onlyNeural arms race in mammalian group only

In all mammalian orders including primatesIn all mammalian orders including primates

Neurobehavioral “Arms Neurobehavioral “Arms race”race”

Monkeys, Great Apes, and Monkeys, Great Apes, and UsUs

Four leaps in braininessFour leaps in braininess

1.1. To PrimateTo Primate

2.2. To AustralopithecusTo Australopithecus

3.3. To HominidTo Hominid

4.4. To Homo sapiensTo Homo sapiens

Brainy NewcomersBrainy Newcomers

Convolution Index = Convolution Index = wrinklinesswrinkliness

• BUT: Cortex width: human 2.9 mm, dolphin 1.7 BUT: Cortex width: human 2.9 mm, dolphin 1.7 mm and conversative (not progressive) mm and conversative (not progressive) organizationorganization

Our Our “Family”“Family”

...And Then There Was ...And Then There Was OneOne • Sixteen Species of Extinct HumansSixteen Species of Extinct Humans • Ardipithecus ramidusArdipithecus ramidus

Australopithecus Australopithecus anamensisanamensisAustralopithecus Australopithecus afarensisafarensisAustralopithecus Australopithecus bahrelghazalibahrelghazaliAustralopithecus Australopithecus aethiopicusaethiopicusParanthropusParanthropus boiseiboiseiParanthropusParanthropus robustusrobustusAustralopithecus Australopithecus africanusafricanusAustralopithecus Australopithecus garhigarhiHomo Homo rudolfensisrudolfensisHomo habilisHomo habilisHomo ergasterHomo ergasterHomo erectusHomo erectusHomo antecessorHomo antecessorHomo heidelbegensisHomo heidelbegensisHomo neanderthalensis Homo neanderthalensis

• Homo sapiens Homo sapiens

We shared planet with two other We shared planet with two other human species as recently as 25,000 human species as recently as 25,000 years ago – years ago – Homo erectus and Homo erectus and NeanderthalsNeanderthals

• Coincided with unstable weather (4 ice ages)Coincided with unstable weather (4 ice ages)

Can human brain get any bigger?Can human brain get any bigger?

HominidHominid Million Million yrsyrs

Weight Weight (g)(g)

AustralopithecusAustralopithecus 5.05.0 500500

H habilisH habilis 2.52.5 725725

H erectusH erectus 1.71.7 10001000

H heidelbergensisH heidelbergensis 0.60.6 12001200

H H neanderthalensisneanderthalensis

0.20.2 15001500

H sapiensH sapiens 0.20.2 13501350

Encephalization abuse within Encephalization abuse within speciesspecies

General Features of Brain EvolutionGeneral Features of Brain Evolution

• Relative increase in brain sizeRelative increase in brain size• Relative increase in telencephalon (cortex) Relative increase in telencephalon (cortex)

over midbrain and hindbrainover midbrain and hindbrain• Relative increase in representation of Relative increase in representation of

sensory information over motor responses sensory information over motor responses • Relative increase in cortex involved in Relative increase in cortex involved in

associative integration than (primary) associative integration than (primary) receptionreception

• Greater differentiation of neocortex, with Greater differentiation of neocortex, with more cell diversity more cell diversity

• Relative importance of biophysical senses Relative importance of biophysical senses over chemical senses in more sentient over chemical senses in more sentient speciesspecies

Convergent evolution in Convergent evolution in all mammalian groupsall mammalian groups of these morphophysiological featuresof these morphophysiological features

Neoteny – Childlike features Neoteny – Childlike features into adulthoodinto adulthood

Bonobo and Common ChimpBonobo and Common Chimp

What did big brain gives us? What did big brain gives us? Social or Cognitive Intelligence?Social or Cognitive Intelligence?

• Example of cognitive: Tool Use in Animals , termite fishing by bonoboExample of cognitive: Tool Use in Animals , termite fishing by bonobo

Social IntelligenceSocial Intelligence

• The Machiavellian HypothesisThe Machiavellian Hypothesis – Richard – Richard Alexander (1970s) suggested that main Alexander (1970s) suggested that main evolutionary pressure behind human intelligence evolutionary pressure behind human intelligence was competition with other people, notably sexual was competition with other people, notably sexual competition between individuals of the same sex.competition between individuals of the same sex.

Dunbar (1992)- natural group Dunbar (1992)- natural group sizesize

Hominid social evolution Hominid social evolution