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
Ecological Explanations
> No non-human primate stores food they must find it
- Food must be found efficiently
- Primates do not move randomly
- They use the most direct path to food - even if not visible
> Frugivores: have larger brains relative to body size than folivores:
- Fruits more challenging to find (competition)
- seasonal distribution (only ripe certain times/places)
- patchily distributed which means larger home ranges
> Primates & other animals are able to do basic math:
-FORAGING strategy : why stay in one area vs another?
if can ct you can determine where to focus your energy
Ecology: Extractive Foragers
All have big brains & all engage in extractive foraging (Aye-aye, Capuchin, Chimp)
EXTRACTIVE Foraging: locating & processing foods encased w/in some other matrix
ex: Aye-Aye:
Brain size as an important life history factor - brain size & aye-aye life history:
-largest brain to body wt of all lemurs
Despite being a strepsirrhine, aye-ayes:
-have relatively larger brain
-wean their infants later using this time to teach their young how to forage
-have females who become reproductive at a later age
**Ecological learning maybe linked to the larger brain & thus a “slow” life history
Social Explanations:
A larger brain allows one to manage social relationships
- Neocortex size correlates w/sociality
- Large groups = many interactions ! You need to keep track of both positive and negative interactions
TRIADIC Awareness if rank & friendship in some species
- is A better friends w/B than A is w/ me?
- Matters if I have a fight w/B & ask A for help
- Capuchins & baboons have triadic awereness of this kind
Chimp kin recognition found chimps can match mother-son but not mother daughter pairs because a migrating female should probably not settle into a community in which many males look like their mother, as these males might be related to her
Machiavellian Intelligence?
Is primate intelligence an adaptation to the special complexities of their social lives, rather than to ecological problems such as finding food?
- Manipulate other for personal gain
- make (& break) alliances and friendships to meet ones own personal needs
Theory of Mind
-Social Manipulation & Deception
Ability to understand the presence of mental states: Beliefs, feelings, intentions, knowledge
Takes two Forms:
1- understand what YOU are thinking
2-Understand what OTHERS are thinking
**Theory of Mind allows predictions of what the other is thinking..how they feel…what they know… & what they will do
Mirror Recognition: Tests of Self
Monkeys & apes differ in their response to mirrors
- Monkeys respond as if it is another monkey or act confused
- Apes eventually use mirror to inspect self (butt)
- Human children dont pass until 1 yrs old
**Not taxon specific - dolphins, giant manta rays, Eurasian magpies, cleaner wrasse (a fish), and some ant species. Few do pass though
Problems? Focuses on visual sense (what about olfaction?) Problems with testing - does it really mean anything?
-Chimp dolls -> capacity for imagination?
Cultural Component:
- Executive brain ratio = vol of neocortex relative to the rest of the brain
- Life History : long lifespans, cultural buffer, social species = allows emphasis on social learning - driving enhanced brain to store info?
Ecology & Social Influences Together?
EX: Chimp hunting an ex of an extremely complicated behavior:
- needs extreme cooperation & planning
- requires “theory of mind” & social learning as well as ecological knowledge
- need understanding of what others “deserve” after the hunt
- requires as least a complex brain
**Brains have been selected for their ability to store & manage info via some combo of individual (asocial) or social learing -> CULTURAL BRAIN HYPOTHESIS
