Modern skulls house a
stone age mind
Basics of Evolutionary
1. Evolutionary Psychologists argue that
natural selection designed our minds
to deal with problems that we faced on
the African savannahs.
– The savannah was our Environment of
Evolutionary Adaptedness (EEA).
Environment of Evolutionary
• Therefore our mind consists of a collection of
adaptations. Each individual adaptation has
evolved to meet challenges faced in our EEA.
• "a characteristic that has arisen through and been
shaped by natural and or sexual selection. It
regularly develops in members of the same species
because it helped to solve problems of survival and
reproduction in the evolutionary ancestry of the
organism. Consequently it can be expected to have
a genetic basis ensuring that the adaptation is
passed through the generations." (Williams, 1966)
The three products of
• Adaptations: Inherited and reliably developing
characteristics that came into existence through
natural selection because they aided in solving
problems related to survival and/or reproduction.
• Example: umbilical cord
• By-products: Characteristics that do not solve
adaptive problems and do not have functional design.
They are coupled to adaptations.
• Example: belly button
• Noise:Random effects produced by genetic drift and
chance mutations that do not affect survival and/or
Behavioral tendencies as
• It can be shown that humans have evolved
physiological traits in response to adaptive
• The brain is the basis of all behavior, and the
brain is a physiological structure that has
evolved over time.
• Therefore, the product of the brain, human
behavior, has evolved certain characteristics
as well to better meet the demands of the
• We can see the cumulative effects of
selective pressures when we observe human
• An evolved psychological mechanism EPM
exists in the form that is does because it
solved a specific adaptive problem.
• EPM’s respond to a narrow range of stimuli.
• Input of an EPM orients the organism to the
adaptive problem it is facing.
• Example: pizza smell vs. snake
• Input to an EPM is subject to decision rules
before producing output.
– Decision rules: if-then statements based upon
• Output can be either physiological activity,
cognitive processing or behavior.
• Output is directed towards solving the
• Important Point: EPM’s that led to effective
solutions in the past may no longer be
effective now (vestigial).
– Example: piloerrection (I.e. goose bumps)
EPM’s lead to behavioral
• EPM’s are not rigid instincts, they
depend upon modulation by the
– E.g., Language.
• Decision rules create response options.
• EPM’s cut down on learning time and
constrain behaviors into a range that
inhibits behaviors that are maladaptive.
• Imagine a population of omnivores that lacked the
capability to digest rancid meat.
– The byproducts of bacterial activity in rancid meat are
therefore toxic to this species.
• Imagine that this species had no EPM to stimulate
avoidance of rancid meat.
• Each individual would have to learn through trial and
error what smells, tastes etc… signaled that meat
was not fit for consumption.
• Now imagine that certain individuals were born with
an aversion to the smell of rancid meat.
• Which individuals would have a higher fitness?
The Standard Social Science
Model (SSSM) and Evolutionary
• SSSM is the prevailing orthodoxy in
anthropology, sociology, and has dominated
psychology since the 1940's.
• The SSSM is under challenge from
Evolutionary Psychology (EP) which has
mounted a critique of contemporary
psychology because it has largely ignored the
role of evolution in shaping human behavior.
According to the SSSM: According to EP:
Body structure (e.g. hands, kidneys, eyes) Body structure (e.g. hands, kidneys, eyes) has
has evolved evolved
There are several types of scientific All science is a single coherent entity consisting of
Endeavour e.g. natural sciences (biology, many disciplines e.g. physics, biology, psychology,
botany, zoology etc.); social sciences sociology etc. - all characterized by adoption of the
(sociology, psychology, politics etc.) scientific method.
Psychology is a social science. Social Biology is a natural science. Biology is built upon the
sciences are concerned with how culture rock of evolutionary theory. Psychology is a branch
and experience produce wide variation in of biology.
human behavior. Therefore social sciences
do not need to consider the role of
evolution in the development of behavioral
Animal behavior is controlled by their Animal and human behavior are biological
biology. Human behavior is determined by phenomena that have evolved.
culture and experience. Animal behavior is Ignorance of evolutionary theory can lead some
more appropriately studied by biologists. psychologists to appear to view humans as having
progressed to be above apes and other 'lower'
animals on a 'scale of nature' or scala naturae.
Humans are born with a few reflexes and The human mind consists of specialized
the ability to learn. Essentially we are modules that are innate and have
'empty computers' or 'blank slates' at evolved via natural and sexual selection
birth, written on by the hand of culture to cope with adaptive problems. Modules
and experience. resemble debugged computer programs
Fodor (1998) expresses this idea as designed for a particular process e.g.
follows: word processor, spreadsheet, database.
"Most cognitive scientists still work in a Fodor (1998) writes that evolutionary
tradition of empiricism and psychologists view
associationism whose main tenets "..the mind as computational system; the
haven't changed much since Locke and mind is massively modular; a lot of
Hume. The human mind is a blank slate mental structure, including a lot of
at birth. Experience writes on the slate, cognitive structure, is innate; a lot of
and association extracts and mental structure, including a lot of
extrapolates whatever trends there are in cognitive structure, is an evolutionary
the record that experience leaves. The adaptation - in particular, the function of
structure of the mind is thus an image, a creature's nervous system is to abet
made a posteriori, of the statistical the propagation of its genome (its selfish
regularities in the world in which it finds gene, as one says)."
itself. I would guess that quite a
substantial majority of cognitive
scientists believe something of this sort;
so deeply, indeed, that many hardly
notice that they do."
Human behavior is controlled by a Modules are specialized to solve
general purpose systems which rely particular adaptive problems: For
on imitation, general intelligence, example, mate selection, language,
culture, reward and punishment. These social co-operation.
systems are content-independent or
Human behavior is acquired during the Modules are inherited from ancestors
lifetime of the individual. who adapted to the EEA. The individual's
internal and external environment plays a
role in the expression of modules. Rather
like setting the preferences for a
Culture determines what is learnt. Culture is a product of specialized
modules. For example a page of text is
the product of a word processing
We can arrive at a conscious decision Many of the reasons for our behavior are
about the best solution to many unconscious
Problems Faced by Ancestral
• Problems of Survival: Getting the organism to
a point where it is capable of reproducing.
• Problems of Mating: Selecting, attracting and
retaining a mate long enough to reproduce.
• Problems of Parenting: Helping offspring
survive long enough that they are capable of
• Problems of aiding genetic relatives: Tasks
relevant to assisting non-descendent kin.
Human Survival Problems
• Food selection: The most general problem in
food selection is how to obtain adequate
amounts of calories and essential vitamins.
– However, we must also avoid poisoning ourselves.
• Plants have adapted toxins that help reduce
the odds that the plant will be eaten.
• Hypothesis: humans have evolved taste
preferences to avoid toxic materials.
• How do we test this?
• Evidence suggests that the materials that
smell and taste bad to humans are also the
materials that are potentially harmful to us.
– Broccoli and brussel sprouts contain
allylisothiocynate which can be toxic in children
(Nesse & Williams 1994)
• We have adaptive mechanisms for removing
harmful materials from our body.
• The percentage of women who experience morning
sickness has been reported to be anywhere from 75 –
89%. However, estimates suggest that the actual %
is near 100.
• Hypothesis: Morning sickness is an adaptation to
avoid consuming teratogens during the critical period
in the development of the fetus.
– Evidence: The foods that pregnant women report to be most
nauseating are correlated with high levels of toxins.
– Evidence: Morning sickness occurs at the same time that the
fetus is most vulnerable to toxins.
– Evidence: Morning sickness decrease around the same time
that the period critical for fetal development has passed.
• Remember, an adaptation must confer an
increase in fitness.
• Hypothesis: Women who do not experience
morning sickness will be more likely to have
problems during their pregnancy.
– Evidence: Women who do not experience M.S.
are 3 times more likely to experience a
spontaneous abortion (Profet, 1992)
Stimulus Expectant vs.
• Expectant • Dependent
– Walking – Driving
– Language (1st) – Reading
– Attachment – Chess
– Love – Algebra
– Sex – Language (2nd)
• In the 60’s John Garcia conducted a series of
studies on taste aversion in rats.
– Rats could quickly associate a novel taste with
sickness even if the sickness did not occur until
hours after experiencing the novel taste.
– Rats could not associate a novel color or texture
with sickness without repeated exposure.
• Harlow (1971) experiments with infant
– Infant monkeys prefer soft terry cloth surrogate
mothers to wire mesh mothers even if only the
wire mesh mothers feed the infants.
• There appears to be adaptive predispositions
to quickly acquire specific associations.
• That is, learning is biologically constrained.
• Organisms can quickly form associations
between stimuli and responses that are (or
were) relevant to their survival in normal
• Fear can be viewed as an adaptive
response to avoid situations that may
lead to injury or death.
• Have humans evolved adaptive fear
responses to specific stimuli? Or do
humans learn fear responses through
Common Fears and Phobias
• The majority of reported fears and phobias
– Spatial stimuli: heights, confined spaces
– Specific animals: snakes, bats, spiders
– The dark
– Public speaking
• There have been very few reported phobias
of electricity, cars, busses, power tools, wood
stoves, lawn mowers, mountain bikes, X-ray
machines, cell phones etc…
• Mineka (1983) observed that rhesus monkeys
raised in captivity did not show a fear
response when confronted with a snake.
• If these monkeys were shown videos of other
monkeys displaying fear in the presence of a
snake the subject monkeys quickly acquired
the same fear response. (same for crocodile)
• If captive raised monkeys were shown a
video of monkeys displaying fear in the
presence of a pot of flowers the subject
monkeys did not acquire a fear response to
flower pots. (same for rabbit)
Prepared Fears in Humans
• Human subjects more quickly form
associations between images of snakes or
spiders and a mild electric shock than
between images of electrical cords or
mushrooms and a mild electric shock.
• They also report that the shocks that occur
after images of snakes and spiders are more
The Case of Language
Inborn Universal Grammar
The Case of Language
•Skinner – like rats
–Associate, imitate, repeat
–Trial and error learning
–Taught how to speak
–Hard-wired for language acquisition
–Endowed with core rules and ability to
apply those rules
The Case of Language
•children do learn language used in
their environment, but:
•rate at which this happens can’t be
explained by learning principles
•children generate all sorts of novel
•rarely exposed to correctly formed
•adults are inconsistent
The Case of Language
•Children apply logical
•General rules for plural forms of
nouns, past tense of verbs
•Impose regular forms on irregular
The Case of Language
There are 3,628,000 ways to
arrange this sentence’s 10 words.
•Language (even sign) just happens.
•Our 5000 languages are dialects of the
universal grammar pre-wired in human
Language Acquisition Device
•LA is like a box - LAD - in which
grammar switches are thrown as
children experience their language.
–English-speaking children learn to put
object last (“She ate an apple.”)
–Japanese-speaking children learn to
put object before verb (“She an apple
–deep structure - meaning
–surface structure - exact wording
–sentences may differ in SS but
convey the same DS, or vice
“John kicked the ball.”
“The ball was kicked by John.”
“Visiting relatives can be a nuisance.”
Mind as Swiss Army Knife
• The human mind is
the Swiss Army
Knife that has all the
• Different species
have different sets