The Primate Brain
Raymond Dart
--raised on a cattle farm in Australia -- excelled in school and won a scholarship to medical school in Sydney. After graduating, served in a medical corps in World War I. --In 1922, became professor of anatomy at the newly founded University of Witwatersrand in Johannesburg, South africa.
primate brains
1) are later than would be expected for our body size 2)are also more complex than those of most mammals 3) have larger areas associated with body control and coordination4) have larger areas associated with visual abilities, learning and intelligence
other amazing feats of the brain : language
1) broca's area : language production, grammar, syntax 2) wernicke's area : language perception and comprehension
two types of tissue in the brain
1) grey matter = color is gray, contains the cell bodies of the neurons, the cerebral cortex is made of gray matter 2) white matter = fibers that connect the neurons into information processing networks. Axons are covered with myelin which is white colored.
types of social learning
1) local enhancement 2) stimulus enhancement 3) emulation 4) imitation
allometry
= study of the change in proportion of various body parts as a consequence of different growth rates. In this context, we are looking at how traits change with body size. Relationship between brain and body size is fairly predictable among primates, with the exception of humans. Humans have brains 3 times the size of what is expected for our body size!
relationship between body size and brain size
Absolute brain size is not a useful measure of comparison or mental abilities. To compare the brains of different organisms...we must understand the relationship between brain size and body size. WE can estimate predicted brain size for a primate, of a particular body size.
social learning
An individual learns a new behavior or behavioral strategy by observing and attempting to reproduce a conspecific's behavior.
Gua and Donald
Chimp and babe: raised together so that scientists could compare the development of language and other skills across species. Brain of modern humans is an evolutionary and developmental outlier - At birth, it has the size of an adult chimp brain and expands by a factor of 2 during the first postnatal year.
neocortex
Cognitive abilities of humans are often attributed to a greatly expanded neocortex : rational of thinking brain--'the crowning achievement of evolution and the biological substrate of human mental prowess'
comparing endocasts
Compared to chimpanzee and bonobo endocasts, the frontal lobes of the Taung endocast are wide (arrows), and the overall shape is more elongated.
what is the brain comprised of?
Comprised of 100 billion info processing cells, calls neurons. Neurons communicate with each other by making connection, called synapses. Estimated there are 60 trillion connections in the human brain. Analogy is that the neurons are similar to the number of trees in the Amazon, and the number of synapses is similar to the number of leaves.
Why is the Hominoid cerebellum unique?
Dentate nucleus has pattern of elaborate folding and increased surface areas. Proposed that this specialization supports the computations necessary for longer and more complex sequences of motor acts. Capacity to flexibly construct and imitate hierarchically nested action sequences underlies specialized extractive foraging skills and tool use.
trendline
Distance above or below the trend line tells us relative size...which can be further quantified as quantifying relative brain size (encephalization quotient)
our social brains
Housing monkeys in larger large increased the amount of gray matter in several parts of the brain involved in social cognition. Particularly areas important in interpreting facial expressions, gestures, and predicting what others intend to do. Also a correlation between gray matter and a monkey's dominance rank--neural circuitry in certain areas promotes or enables social success.
other amazing feats of the brain: memory
Humans have exceptional short and long term memory capabilities. There are three basic processes 1) encoding : storing info 2) maintenance : keeping it alive 3) retrieval : finding encoded info. We can ask humans what they remember, but how would you test memory of the other living primates?
comparing brains
Humans have larger brains than the other living primates. However, we must take body size into consideration. Larger organisms tend to have larger brains.
Taung Child
In 1924, learned of a fossil baboon skull found at a nearby limestone quarry at Taunt. Asked to be sent any more bones or fossils that were found. The first two crates arrived in November of that year, and Dart found a fossil cast of the inside of a primate skull. Taunt child was about 3 years old: full face, teeth and jaws, endocranial cast of the brain.
the human brain
In comparison to other mammals...our skulls are rounded to accommodate a large brain, our faces are smaller and flatter than other organisms.
do apes show language
Kanzi, a bonobo. Washoe, a chimp. Koko, a gorilla : 'koko love', 'baby' , 'gorilla' , 'good'
social learning
Many primates rely extensively on learned behavior. This can be demonstrated by introduction of new behaviors into a group that are subsequently learned by others. On the island of Koshima, macaques were provisions with yams. Imo began washing the yams, and this spread throughout the group. She also invented the method method of separating wheat from sand.
brain cell development of the human brain
Nearly half of your brain cells are developed during the first of pregnancy. Actually, an infant has twice as many cells and connections as an adult! Development requires pruning back of this overproduction. Brain development continues after birth, through adolescence.
why are our brains so big?
Numerous studies have found correlations between size of social networks and that of specific areas of the brain linked to sociality. One study found a positive relationship between gray matter and number of Facebook friends.
encephalization quotient
Relative brain size can be quantified using the Encephalization Quotient. More refined measurement than the brain to body mass ratio because it takes into account allometric effects. EQ = observed brain volume / predicted brain volume . Humans have a 5.1 to 7.4 EQ, chimps have a 2.2.
Do apes show advanced memory?
Research at the primate research institute in Japan has revealed that chimpanzees have excellent short term memory. Their capacity in this realm may exceed that of humans. What is the adaptive advantage of having such skills?
why are out brains so big!
Social Brain hypothesis = brain size (particularly the size of the neocortex) shows a relationship with the size a species' social group. Keeping track of who is doing what to whom requires considerable processing power...and so bigger groups, demand bigger brains.
quick tour of the anatomy of the brain
The human brain is modular : cerebrum, cerebellum, medulla.
other aspects of the human brain
The human brain is not only larger than that of other mammals, but also shows expansion of the prefrontal cortex.
other aspects of the human brain
The human brain is not only larger than that of other mammals, but also shows increased convolution (folding of brain tissue). While the neocortext is smooth in mice and some small mammals, it has deep grooves and wrinkles in primates and several other mammals. This means the brain of a human child with the same volume as a chimpanzee has more cerebral cortex.
benefit of social learning
Those with ability to learn socially may increase reproductive success...1) take advantage of things learned by other members of the group 2) pass on skills to their offspring that would other 3) exploit the past experiences elders in key circumstances (such as droughts). Processes of organic evolution may be supplemented by cultural evolution.
our plastic brains
To qualify as a licensed london taxi driver, a trainee must acquire the knowledge--the complex layout of central London's 25,000 streets and thousands of places of interest. Previous studies showed greater volume of grey matter in posterior hippocampus, relative to non taxi drivers. This study looked at the same individuals...before they started studying, and then after. Found that acquiring 'the knowledge' caused changes in the taxi drivers' brains.
primate brains
Trendline shows the expected brain size for a given body. Above the trend line - bigger than expected. Primates have large brains! (are above the line, and humans are the most above the line)
human cognition
What makes human cognition different is not more individual brainpower, but rather : the ability to learn through other persons and their artifacts, the ability to collaborate with others in collective activities
do apes show insight
Wolfgang Kohler's the mentality of apes (1917, german) provides classic examples
medulla
automatic actions, such as breathing and digestion
bones to behavior
brains are great, but how can we study soft tissue in extinct hominids? Surface of the brain has been preserved in some fossilized specimens!
The human brain is not only larger than that of other mammals but also
consumes more energy! : -- brains of dogs and cats use 4 to 6% of their body metabolism -- old world monkey brain uses 9% of their body metabolism --human brain uses 20% of their body metabolism
cerebrum
directs the conscious or volitional motor functions of the body, sense
limbic brain
emotional or feeling brain
endocast
external cast of a hollow object
behavioral reflections of the brain
greater size and complexity of the primate brain is reflect in behaviors : social cognition, and learning. The strong relationship between reproduction, care of offspring and learning. Primates spend a longer time growing up, both biologically and socially...they have much to learn about their environment and society!
prefrontal cortex
has been implicated in planning complex cognitive behaviors, personality expression and decision making
comparing brains, bodies, and lifestyle
increase in brain size occurred relatively late in the evolution of our lineage. There has been a three fold increase in brain size over the last 4 million years!
other amazing feats of the brain: insight
insight = a penetrating and often sudden understanding of a complex situation or problem. More technical definitions of insight...-capacity for understanding one's own or another's mental processes. Immediate understanding of the significance of an event or action.
reptilian brain
instinctual or dinosaur brain
imitation
learning from seeing it be done, learning about the form of the act. Observers attempt to reproduce the change of state in the world that the demonstrator produced, but do so using their idiosyncratic methods. They achieve the same ends, but not using the same means. In the past, it was claimed that apes (other than humans) had only emulative abilities. Imitation can be differentiated by emulation by the form of the act. Very similar between the model and the learner, even in not adaptive. Imitation is a quick way of acquiring a complex skill, while avoiding costly errors. Not as relevant to simpler tasks, where one can learn by trial and error. Previously considered to be uniquely human.
emulation
learning from seeing the end result, not how to accomplish the task. Observers attempt to reproduce the change of state in the world that the demonstrator produced, but do so using their own idiosyncratic methods. They achieve the same ends, but not using the same means. In the past, it was claimed that apes (other than humans ) had only emulative abilities.
cerebellum
motion, balance, learning, planning, and comprehension of complex sequences. Don't overlook the cerebellum: Human cerebellum contains 4X more neurons than the neocortex. Cerebellum underwent rapid size increase throughout the evolution of apes. Humans have significantly larger cerebella relative to neocortex size than other anthropoid primates. Humans have neocortex that is 818% larger than baboon, but cerebellum is 940% larger.
individual versus social learning
one can learn individually through trial and error, but this many not always be the most efficient or safe means of acquiring information. In what ways could primates augment their own individual acquired knowledge and skills?
cerebral cortex
sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. Plays a critical role in memory, attention, perceptual awareness, thought, language, and consciousness. The human cerebral cortex is 2-4 mm.
local enhancement
transmission of behavior by attention being drawn to a particular locale in the environment. Transmission of behavior the learner's attention being drawn a particular locale in the environment. Example : parties of chimpanzee being attracted to tool use sites. Do not learn about the particular technique or goal, but are attracted to sites which may facilitate the behavior.
stimulus enhancement
transmission of behavior by attention being drawn to an object or part of an object, irrespective of its location. In situations of stimulus enhancement, the probability of an animal approaching or contacting something is increased by seeing an individual interacting with it. Once your attention is focused on a particular object, then your ability to learn by trail an derror is increased.