The Biological Roots of Behavior

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The Biological Roots of Behavior

• Part I the complex interaction between our genes
  and the environment to the music of evolution

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Geneticsthe basics

• Chromosomes strands of hereditary material
• Humans have 46 23 from their mother, 23 from
  their father
• Found in the nucleus of each cell
• The master blueprint or recipe for each individual

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Genetic basics ii

• Genes sections along a chromosome which control
  the chemical reactions that direct development
• Humans have around 25,000
• Composed of DNA
• Play an essential role in not only in how we
  develop, but when we develop, as switches,
  turning other genes off on
• 2001- the Human Genome Project

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Does one gene control anything?

• Media reports seem to indicate that certain genes
  are responsible for certain traits or abilities.
• True or false?
• Very few traits or abilities are controlled by a
  single gene, most rely on an interaction between
  several genes and the environment.

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Nature vs. nurture ?

• Is the person we are today a result of the genes
  we inherited from our parents?
• Or, instead, are our traits, abilities, strengths
  and weaknesses caused by our environment?
• This question, which caused furious debate for
  centuries, has been answered.

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A mysterious dance

• Now we know that neither nature (genes) nor
  nurture (the environment) are primarily
  responsible for the person we are.
• A complex, ever-changing, interaction between
  these two forces creates the complex, unique
  people we are today, ready to change as our lives
  and circumstances do.

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Why are we so similar?

• 6 billion and counting, yet we are remarkably
  alike
• How can this be?
• Evolutionary psychologists claim that this is due
  to genetic qualities, carried in our DNA that
  developed while we evolved from our ancestors

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Mental Modules

• Evolutionary psychologists - mind not as a
  general-purpose computer waiting to be programmed
  by our experiences
• Instead, a collection of specialized and
  independent modules developed to solve specific
  survival problems
• One module often involves different parts of the
  brain working together

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Born to conquer

• These mental modules are put into place by
  messages from our DNA as we mature
• They allow us to be proficient at various tasks
  and abilities without much, or any, experience or
  teaching

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We all share

• Without any work or effort, and at an early age,
  humans show certain characteristics
• a) Infant reflexes no one needs to teach
  us to nurse
• b) curiosity we are eager to try new
  things and manipulate objects
• c) play develops physical/social skills

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Our innate cognitive tool set

• At birth we can
• a) interpret gestures expressions,
• b) identify faces,
• c) understand what others are thinking or
  feeling,
• d) understand, to some extent, numbers
• e) acquire language

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The wonder and mystery of Language

• How do we readily turn random sounds into words
  and sentences that convey thoughts, feelings and
  complex information?
• Darwin said that there is something unique and
  special about the human brain that allows a baby,
  with limited aide from the environment, quickly
  master language.

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Dont animals have language?

• Yes, but only in a limited sense.
• Chimpanzees, gorillas and even parrots can, with
  exhaustive coaching, pick up many aspects of
  language
• But its not easy or natural
• Humans, on the other hand, develop extraordinary
  language abilities naturally given the most basic
  of opportunities

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Languages key ability

• But still, many animals communicate in their
  environment, isnt that language?
• Not in the fullest sense.
• A true language must have productivity the
  capacity to express an infinite number of novel
  utterances, right there on the spot, as
  circumstances demand

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The puzzle of language development

• How do we learn to talk (sign)?
• Is it through imitation and positive
  reinforcement?
• Partially, but not completely.
• Poverty of stimulus adults do not give children
  sufficient instruction to explain their rapid
  acquisition of proper language

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How do we do it?

• Noam Chomsky, way back in 1957, claimed that we
  are all born a mental module, the language
  acquisition device, that is just waiting, as the
  child matures, to understand and use universal
  grammar
• We are born with a software package that
  employs primitive grammar and understands nouns,
  verbs, negatives, etc.

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Evidence supporting Chomsky

• 1) World-wide consistency
• 2) Novel word combinations
• 3) Poor or non-existent adult modeling
• 4) Spontaneous language development

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On the other hand ..

• Intense observation of mothers interacting with
  infants showed much more interaction than
  researchers had anticipated
• The power of positive reinforcement
• Expansions

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Evolutionary perspective?

• This amazing facility for language evolved,
  through natural selection, because it helped
  humans survive and have children who also
  survived to have children
• We could, easily and precisely, tell each other
  about dangers and opportunities, as well as
  cooperate and band together

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Physical evidence?

• Genes have been located which conclusively
  influence language development
• Brain structures (left hemisphere) also have a
  direct link to language capabilities
• a) Wernickes area - comprehension
• b) Brocas area - production
• c) Heschls gyrus learning a new
  language

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But what about behavior?

• Sure, some capacities have developed through
  evolutionary processes we see it in the brain
  and genes
• Complex social behaviors though?
• The realm of sociobiology evolutionary
  explanations for social behaviors, including
  humans

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Sociobiology examples

• Jackal helpers why do they sacrifice their
  own reproductive opportunities?
• Mongoose rescues
• Lion infanticide

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Humans?

• Can we explain the origins of human behaviors?
• Junk food obsessions
• Social behaviors?
• Niece/nephew adulation

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Better yet, .

• Do male and female sexual strategies arise from
  evolutionary influences?
• Huge controversy

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David Buss big question

• What do males and females look for in a mate?
• In 37 wildly different countries he found the
  same answers
• From Scandinavia to the South Pacific they were
  looking for the same thing

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Males like

• Why do women try so hard to look young and
  healthy?
• Because those are the qualities that men, all
  over the world, select in picking a wife.
• They offer the best chance of producing the most
  children.

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What women really want

• Why do men, everywhere, strive so hard for
  status, dominance and ?
• Because that is what women look for in a mate.
• Someone who could provide a stable home and
  adequate resources to raise children.

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Other Points

• Evolution is a battle fought by individuals not
  species.
• Its not really, the survival of the fittest.
• More accurately, it is. You must breed to
  succeed.

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It takes all kinds

• Evolution explains why we share basic features
  and capabilities
• But why are we so different?
• We have inherited differing traits

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Heritability

• an estimate of the variance within a population
  that is due to genetics
• A measure of nature, excluding nurture
• Ranges from 0 (no genetic influence) to 1

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Measuring heritability

• The heritability of a behavior is estimated in
  three ways
• 1) comparing monozygotic (identical) and
  diozygotic (fraternal) twins
• 2) looking at identical twins raised in
  different households
• 3) seeing whether children more closely resemble
  their adoptive or biological parents

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Limits on heritability

• Applies only to a group living in a particular
  environment
• Children who face severe malnutrition might not
  grow very tall, even if their parents were giants
  

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IQ and Heritability

• Strong relationship up to 87 for identical
  twins raised together
• Amazingly, the genetic influence grows even
  stronger as we age
• Correlations between those adopted and their
  adopted family disappear altogether

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What about group differences?

• We find consistent differences between races.
• Are some races genetically inferior?
• Huge controversy
• Long history
• The Bell Jar

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Group differences in IQ
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Why its not the genes

• The Tomato Plant Experiment
• Differing environments lead to different outcomes
• Expectations
• Overlap
• Raised elsewhere?
• African purity means nothing

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The guy you are talking to

• Heritability estimates dont tell us anything
  about an individual, just a large group
• Huge numbers
• Big overlap
• Tremendous variations in environment
• Your genetic blueprint and your environment are
  unique

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Nature or Nurture

• It is the interaction of our genes and the
  environment in which they are expressed that
  determine our behavior, experiences and
  personality

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Genes behavior

• Researchers have found moderate levels of
  heritability for almost all behaviors
• Some genes influence behavior directly
• But often genes influence our behavior indirectly
  by giving us advantages or deficits that have
  great effect on both what we do within our
  environment and how it responds to us