Exam 3: Primate Brains, Cognition, and Behavior Flashcards
Are Primates Especially Intelligent?
Primates are behaviorally plastic -> Cultural traditions
Primates are “intelligent” if defined by:
- Negotiate life in complex social systems
- Solve difficult ecological problems
- Exceptional learning capacities
Evidence for unique primate intelligence?
Primates have a # of anatomical & physiological features which may relate to behavioral plasticity.
** The most important of course are BRAINS
Comparing Brains:
- many same basic “parts”
- HUMANS: have larger overall & more cortical folding than other primates = MORE NEURONS
Paul D. Macleans “Triune Brain” - thought to describe the “evolution” of the mammalian brain (1960s)
Three Parts:
- Reptilian Brain: basic instinctual behavior like mating, aggression
- Paleomammalian Brain (aka Limbic): Emotions/memory
- Neomammalian Brain: Abstract thought & cognition
However now thought to be too simplistic & many nonmammals have these abilities w/out the same “parts”
EX: Bird Brains: organized diff from primate brains. Mammals & bird brains have been evolving down separate paths over 300 million yrs
**Brain areas important for high-level cognition such as long term memory & problem solving are wired up to other regions of the brain in a similar way
Relative Brain Size - Another Story
body wt/brain wt
Primate brains are RELATIVELY LARGE in comparison to most other vertebrates
- Humans are above the red line which suggests something is going on
- However *SOCIAL ANIMALS like Cetaceans (porpoises), crows, wolves also show this pattern
**Absolute brain size vs Relative brain size => matters
Encephalization Quotient (EQ):
ratio btwn actual brain mass & predicted brain mass for an animal of a given size
- *HOWEVER neither brain size alone, nor brain size in relation to body size (EQ) may be the whole story
- We can also look at the relative size of DIFFERENT PARTS of the brain
Parts of the Brain:
- Reptilian Brain: Survive, react, repeat, repeat
- Midbrain: Feel, remember, interact w/others
- Neocortex: Abstract thought - talk - think- move- create- learn
- Cerebellum: doesnt change alot among diff species
*NOT all parts of the brain do the SAME thing
Neocortex vs Body size
- Neocortex is the most recent evolved portion of the cerebral cortex
- Where info from diff senses is integrated; controls conscious thought.
The neocortex where conscious thought occurs:
- 30-40% of brain vol. in most mammals
- 50-80% in primates -> more emphasized in primates
Phylogenetic effects : Relative size of neocortex to medulla (part of the primitive brain)
- Insectivorous mammals: neocortex same size as medulla
- Strepsirrhine primates : neocortex 10x larger
- Haplorrhine primates: neocortex 20-50x larger
- Humans - neocortex: 105x larger
AND Primate brains are NOT all the same!!
Phylogenetic effects exist in size & capacity
- Strepsirrhines have smaller relative brain size, small neocortex than happlorrhines
- Happlorrhines have higher neuron density
- Apres have larger relative brain size than most monkeys (except Capuchins**)
Why Big Brains?
Difficult to answer since brains are so expensive:
- around 8x the cost of muscle tissue
- In humans: the brain accts for 2% of body mass & about 20% energy expenditure
- Big brain is NOT always Beneficial
Natural Selection
Only allows for big brain if beneficial over small brain
- cant spend energy elsewhere
- tradeoffs w/other needs
ex: weird bat: Brains vs Testes
- Promiscuous: small brain, large testes
- Monogamous: big brain, small testes
* Tradeoff: reproduction vs smarts!!
Brain size is correlated w/ a # of variables
diet, social structure, longevity, locomotion…
TWO major reasons for big brains:
- Ecological Hypothesis
2. Social Hypothesis