Transcript Lecture 9A

Brodmann measured the PFC size as percent of the total
cortex using the cytoarchitectonic method:
29% of in humans,
17% in the chimpanzee,
11.5% in the gibbon and the macaque,
8.5% in the lemur (Prosimians of Madagascar) ,
7% in the dog, and
3.5% in the cat
PFC-associated evolution
1. Inhibitory functions of the PFC (The candy
game)
2. Social function of the PFC (by British
anthropologist Robin Dunbar)
3. PFC-controlled synthesis of neuronal
ensembles (mental synthesis)
Candy Game by
Sally Boysen
• The Candy Game is played by two chimpanzees, Sheba
and Sara, who have been put in a room together.
• A researcher offers two unequal arrays of candy to Sheba.
• Whichever tray Sheba points to is given to Sara, and Sheba
receives the other tray (the one she did not point to).
• Therefore, to get a bigger array of candy, Sheba has to
point to the tray with a smaller array of candy.
• Human adults learn this lesson quickly
after a single trial, but chimpanzees are
just unable to behave “rationally” when they see candy.
• Even after 400 trials, they still point to the larger array of candy
and end up with the smaller amount. It's not that chimpanzees
don't try.
• They seem to know that they are getting it wrong.
• After every unsuccessful attempt, Sheba’s face is twisted in a
grimace and she slams her fist down on the experimental
apparatus in frustration.
• If I didn’t tell you anything else, what would your conclusion
be on chimps rational / abstract thinking abilities?
• The researcher, Dr. Sally Boyson, trained chimpanzees to recognize Arabic
numbers written on plastic chips. After Sheba demonstrated her
understanding of Arabic numbers, Boyson repeated the Candy Game but
replaced the candies with plastic chips.
• For example, Sheba would be presented with two chips with the numbers
one and six. If Sheba picks a plastic chip with the number six, Sara gets six
candies and Sheba gets one candy.
• Dealing with plastic instead of candies, chimpanzees quickly learn to pick
the smaller Arabic number and get the bigger reward for themselves.
• Thinking of candies in terms of symbols (Arabic numbers) allows the
chimpanzees to get what they want.
• Boyson explains: “The poor performance with candy arrays
observed in the present study may reflect a simple but
generally adaptive perceptual strategy that would likely
be appropriate under natural foraging conditions, a
strategy that would permit a chimpanzee to respond to a
larger, more concentrated food source with minimal
higher level cognitive processing.”
• In other words, chimpanzees have a shortcut system in
their brain that quickly selects a bigger array of food. This
system (most likely part of the phylogenetically older
subcortical brain regions) acts so quickly and strongly at the
sight of candies that the rational input from the neocortex
is arriving too late.
• The PFC-driven inhibitory signal arrives just a little bit too
late – the chimpanzee has already pointed to the bigger
array of candies.
• There are no candies in sight and therefore
no urge to grab them
• The use of symbols as representations
for quantities of food freed the chimpanzees
from the tyranny of the fast-acting limbic system.
• The associative memory between the Arabic numbers (symbols)
and the number of elements in an array are stored in neocortex.
• To react to symbols, chimpanzees have to interpret the Arabic
numbers (so any decision has to wait for this interpretation by
neocortex) and only then decide which Arabic number
corresponds to a greater array of items using their rational
neocortex.
• As a result of slowing down of decision making process, the PFC
has time to select a correct action that will lead to a greater
reward.
• While in the wild, the fast-acting limbic system is indispensible –
every millisecond is important when reacting to a predator – in the
Candy Game the subcortical system forces chimpanzees into
suboptimal performance.
•
…I can relate to chimps. During an argument with my wife, my fast-acting limbic system often gets
before the rational thinking neocortex; the basal ganglia throws words before the cortex…
Candy Game for human children
• James Russell of Cambridge University
devised a version of the Candy Game for
human children (Russell J, 1991). This was a game
played between a child and an experimenter in which a
child tried to win chocolates.
• In the training phase, the child was presented with two
opaque closed boxes, one of which contained a
chocolate. Once the child selected a box, by pointing, it
was opened by the experimenter. If the child had
selected an empty box, the other box would be opened
and the child would be given a chocolate.
• Thus, in the training phase, the child learned that he
must select the empty box in order to be rewarded with
the chocolate from the other box.
• In the testing phase, the boxes had large windows
facing the child so he could see which was the
empty box.
• The 4-year-olds, but not the 3-year-olds, pointed to
the empty box on the first trial. Moreover, the 3year-old children frequently continued to point to
the box filled with chocolate for the full 20 test
trials.
• Like the chimpanzees, they were overpowered by
the initial reaction of pointing to sweets, instead of
the rational choice of selecting an empty box in
order to get the chocolates.
• The Candy Game illustrates that the presence of ‘symbolic thinking’ is
necessary but not sufficient for successful performance in the Candy Game
 the brain also needs an ability to control the first impulse.
• The crucial difference between the four-year-olds and three-year-olds and
between adult humans and chimpanzees may not be in ‘symbolic thinking’
per se as much as in the ability to control the first impulse coming from
subcortical regions:
• both three-year-olds and chimpanzees are able to think symbolically using
abstract symbols stored in their rational cerebral cortexes, but humans after
the age of four are able to put their PFC into the driving seat of their
behavior.
• Between the age of three and four, a child’s brain matures to enable the
rational PFC to control the initial impulse of the subcortical structures.
• Conclusion: when interpreting
any experiment with animals
beware of behavioral shortcuts.
If you want to test the slower
neocortex, make sure that you
conduct an experiment in a
manner that allows neocortex
to react
Social function of the PFC (by British
anthropologist Robin Dunbar)
• “…way of reducing the risk of predation is to live in
large groups. Groups reduce the risk in a number of ways.
• One is simply by providing more eyes to detect stalking predators.
• Larger groups are also an advantage as a deterrent. Baboons have been known to
drive leopards up a tree, and have occasionally even killed them. Red colo bus
monkeys are significantly less likely to be attacked by chimpanzees if an adult male
of their group is nearby; even chimps seem unwilling to risk a mass counter-attack
launched by an animal that's barely a quarter of their own weight.
• Last but not least, a group creates confusion in a predator. Predators succeed by
locking on to a target animal and running it down. When the prey runs into a group,
there are animals running every which way and the predator becomes momentarily
confused. That moment of lost attention is often just enough for the prey to make
good its escape.
• So primates live in groups as a mutual defence against predation. Indeed, sociality
is at the very core of primate existence; it is their principal evolutionary strategy,
the thing that marks them out as different from all other species. It is a very special
kind of sociality, for it is based on intense bonds between group members, with
kinship often providing a platform for these relationships. Primate groups have a
continuity through time, a history built on kinship (usually mother-daughter
relationships, but very occasionally father-son ones too).”
Group size increased
• “Social animals hang in perpetual balance
between two forces: the centripetal forces,
driven by fear of predation, which have
produced the feelings of sociableness that
make us seek out company; and the centrifugal
forces, generated by overcrowding, that send
us scurrying for the sanity of a solitary life.
When predators become common (and for
humans, those predators can just as easily be
neighbouring human groups rampaging
through your territory on raids), we hanker for
the close proximity of friends and tolerate all
kinds of overcrowding. When predators are
rare, the stresses of crowding overwhelm us
and we disperse. Group size is the product of
this balancing act.”
• Group size increased in humans to about 150
from about 50 in chimps
• Inside a group primates form alliances.
Alliances are complex matter. One must
develop Theory of mind neocortex increased
Theory of mind
• Theory of mind - ability to understand that others have mental
states and perspectives different than our own
• Robin Dunbar: “The deliberations of the last decade have shown
that the central issue is something that psychologists now rather
confusingly refer to as a 'Theory of Mind' (or ToM for short). Having
a Theory of Mind mea ns being able to understand what another
individual is thinking, to ascribe beliefs, desires, fears and hopes to
someone else, and to believe that they really do experience these
feelings as mental states. We can conceive of a kind of natural
hierarchy: you can have a mental state (a belief about something)
and 1 can have a mental state about your mental state (a belief
about a belief) . If your mental state is a belief about my mental
state, then we can say that '1 believe that you believe that I believe
something to be the case'. These are now usually referred to as
orders of 'intensionality'. I Thinking about mental states in this way
yields the fo llowing rough hierarchy.“
Social function of the PFC (by British
anthropologist Robin Dunbar)
• Robin Dunbar: “These alliances are established and maintained by grooming, the
most social activity in which monkeys and apes engage. In some species, as much
as a fifth of the entire day may be spent grooming, or being groomed by, other
group members.”
• “The central argument revolves around four key points: (I) among primates, social
group size appears to be limited by the size of the species' neocortex; (2) the size of
human social networks appears to be limited for similar reasons to a value of
around 150; (3) the time devoted to social grooming by primates is directly related
to group size because it plays a crucial role in bonding groups; and finally, (4) it is
suggested that language evolved among humans to replace social grooming
because the grooming time required by our large groups made impossible
demands on our time. ” …*
• “The conventional view is that language evolved to enable males to do things like
co-ordinate hunts more effectively. This is the 'there's a herd of bison down by the
lake' view of language. An alternative view might be that language evolved to
enable the exchange of highfalutin stories about the supernatural or the tribe's
origins. The hypothesis I am proposing is diametrically opposed to ideas like these,
which formally or informally have dominated everyone's thinking in disciplines
from anthropology to linguistics and palaeontology. In a nutshell, I am suggesting
that language evolved to allow us to gossip.”
Theory of mind in apes
• Tomasello, 2016: Researchers showed the chimpanzees, bonobos
and orangutans a series of videos starring a regular person and a
man dressed up as King Kong. In a variety of scenarios, King Kong
would try to hide a rock-like object from the person.
• Scientists recorded the eye movements of three great ape species
while the animals watched videos of a man searching for a hidden
object that had been moved without his knowledge
• they looked more frequently at the location where the man
expected the object to be (a belief the apes knew was false), even
though the object was no longer there.
• The findings suggest the apes were able to intuit what the human
was thinking.
• Tecumseh Fitch: “final nail in the coffin of the long-standing idea
that humans are the only species with ‘theory of mind.’”
Evolution of the PFCcontrolled synthesis of
neuronal ensembles
1. Daniel Povinelli: Chimpanzees do not ask the
questions ‘why‘ and ‘how’, unlike children they do
not investigate why the modified block cannot
stand on it own.
2. Chimps lack the concept of weight
• - DANIEL J. POVINELLI (20min, 2013) https://www.youtube.com/watch?v=kX49dlbfG9E
• experiment with weight concept in chimpanzees
(8min, 2012):
https://www.youtube.com/watch?v=pdvRhs4z1CI
External manifestation of mental
synthesis in humans
Verbal Manifestations: communication of new images to a listener
1. Syntactic communication system
2. Storytelling
3. Active teaching
Creative Manifestations: mental synthesis of new objects
4. Representational art
5. Creativity and innovation
6. Design and construction
7. Natural sciences (seeking an explanation for invisible forces)
Behavioral Manifestations: mental synthesis manifests itself in pursuits that
are based around imagination
8. Pretend play
9. Strategy games
10. Religious beliefs
1. Chimpanzees do not ask the questions
‘why‘ and ‘how’; unlike children they do not
investigate why the modified block cannot
stand on its own 
2. Chimps lack mental synthesis
Synchronization
no enhanced
connections
Asynchronously
firing neuronal
ensembles
Perceived as
two different
objects
Synchronously
firing neuronal
ensembles
Perceived as
one morphed
image
• Stop here