The Genetics of Behavior

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The Genetics of Behavior

• Are we nature or nurture?

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Two basic views

• Nativists
• Empiricists

Emphasize genes and inborn characteristics
Emphasize learning and experience
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Evolutionary Psychology

• Emphasizes evolutionary mechanisms that may help
  explain human commonalities in
• Cognition, development, emotion, social practices
  and other behavior.

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Behavioral Genetics

• An interdisciplinary field of study concerned
  with the genetic basis of behavior and
  personality.

5
An Understanding

• All scientists understand there is an interaction
  between heredity and environment.
• Set point - a genetically influenced weight
  control mechanism vs. obesity in the US.

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The Secrets of Genes

• Genes - are the basic units of heredity located
  on chromosomes which contain threadlike strands
  of DNA.
• Egg and Sperm contain 23 chromosomes each.
• Creating the genome

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Genome and what it means

• After conception each cell has 23 pairs of
  chromosomes. (46)
• Most traits depend on more than one gene pair.

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How are traits studied?

• Linkage studies - look for patterns of
  inheritance of genetic markers in large families.
• A genetic marker is a segment of DNA that varies
  among individuals.

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The Genetics of Similarity

• Evolution is a change in gene frequencies within
  a population over many generations. (mutation)
• Natural Selection is a process in which
  individuals adapt to a particular environment and
  survive.

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Evolutionary Psychologists

• They look to the prehistoric record to draw
  inferences about behavior that solved survival
  problems
• Because of evolutionary history some qualities
  are universal

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Evolutionary Psychologists

• Universal qualities are.
• Reflexes
• Attraction to novelty
• A desire to explore and manipulate objects
• An impulse to play and fool around
• Basic mental skills

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Our Human Heritage

• The origins of perception
• Sensation - the detection of physical energy
  emitted or reflected by physical objects.
• Perception - the process by which the brain
  organizes and interprets sensory information

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Our Human Heritage

• Some abilities develop from certain experiences
  at certain times.
• Complex features are processed by specialized
  detectors
• Inborn perceptual abilities include
• Startle reflex 3. Voice recognition
• Audio location 4. Discrimination of smells

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The Face of Emotion

• Some expressions are universal and present from
  birth
• Universal facial expressions function in
  communication.

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Sociability and Attachment

• Synchrony and sociability
• Newborns are sociable from birth
• They pay attention to human faces and show
  synchrony
• Attachment - the emotional tie that children and
  their caregivers feel toward each other

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Sociability and Attachment

• Attachments contd
• Contact comfort which is the innate pleasure
  derived from close physical contact.
• Infants who do not develop secure attachments may
  develop emotional and physical problems.

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The Capacity for Language

• Language is a system for combining meaningless
  elements into utterances that convey meaning.
• A childs vocabulary increases at a rapid rate.

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Language Development

• Requires the mastering of a complex set of rules
  including
• Surface structure - the way a sentence is
  actually spoken
• Deep structure - the meaning inferred by a
  sentence
• Syntax - the rules of grammar

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Language Development

• Children do not simply imitate adults
• They are able to perceive deep structure
• Noam Chomsky theorized that we have a
  biologically based language acquisition device
  that aids in language development.

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Chomskys Examples

• Children of different cultures go through similar
  stages of linguistic development

• Children combine words in ways that adults never
  would
• Adults do not consistently correct their
  childrens syntax yet they learn to speak or sign
  correctly.

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Chomskys Examples

• Even children who are profoundly retarded acquire
  language.

• Infants as young as 7 months can derive simple
  linguistic rules from a string of sounds.

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Does Nurture Play a Role?

• Imitation does play a role because parents
  correct the childs ungrammatical sentence.
• There appears to be a window of opportunity to
  learn language.

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Evolution, Courtship and Mating

• Sociobiology - an interdisciplinary field that
  emphasizes evolutionary explanations of social
  behavior in animals.
• The view is that nature has selected
  psychological traits and social customs that
  promote propagation.

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Evolution, Courtship, and Mating

• Sociobiologists argue that males and females have
  evolved different mating strategies.
• Males to inseminate as many females as possible
  and females be more selective.
• As a result, males are thought to be more
  promiscuous and drawn to sexual novelty, females
  are more interested in stability.

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Sociobiology vs. Evolutionary

• Sociobiologists tend to argue by analogy to
  nonhuman animals. Evolutionary biologists
  recognize these are simplistic and misleading.
• Critics argue that evolutionary explanations are
  based on stereotype of gender. Theories are also
  nonfalsifiable.

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The Genetics of Difference

• Heritability - is the statistical estimate of the
  proportion of the total variance in some trait
  that is attributable to genetic differences among
  individuals within the group

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The Genetics of Difference

1. An estimate of heritability applies only to a
   particular group living in an particular
   environment.
2. Heritability estimates do not apply to
   individuals, only to variations within a group.
3. Even highly heritable traits can be modified by
   the environment.

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Computing Heritability

• Research methods are used in an attempt to infer
  heritability by studying people whose degree of
  genetic similarity is know.
• Adopted children share half their genes but not
  environments with birth parents.

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Computing Heritability

• Identical (monozygotic) twins develop when a
  fertilized egg divides into two parts.
• Fraternal (dizygotic) twins develop from two
  separate eggs fertilized by different sperm.
• Identical twins raised apart from each other are
  of special interest because they have identical
  genes but a different environment.

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Heritability and Intelligence

• Intelligence quotient (IQ) - is a measure of
  intelligence originally computed by dividing a
  persons mental age by his or her chronological
  age multiplied by 100
• Currently it is norms based.

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Genes and Individual Differences

• IQ scores are highly heritable with estimates
  averaging around .50 in children and .60 to .80
  in adults.
• Scores of identical twins are always more highly
  correlated than those of fraternal twins.
• Scores with adopted children correlate higher
  with birth parents vs. adoptive parents.

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The Question of Group Difference

• Race differences are controversial
• Asians as a group score higher than whites who
  score higher than African Americans.
• Some theorists have confused intra-group findings
  with inter-group.

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The Question of Group Difference

• Minority children tend to have access to fewer
  educational and material resources.
• Well designed studies have failed to reveal
  genetic differences.

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Genes and Personality

• Temperaments - physiological dispositions to
  respond to the environment in certain ways
  present in infancy and are assumed to be innate.

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Heredity and Temperament

• Differences in childrens temperaments appear
  early in childhood.
• Temperaments tend to remain stable throughout
  childhood.

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Heredity and Traits

• A trait is a characteristic of an individual,
  describing a habitual way of behaving, thinking
  and feeling.

• Clusters of measures or scores that are highly
  correlated are assumed to measure the same
  underlying trait or ability.

• Factor analysis - a statistical method for
  analyzing the inter-correlations among different
  measures now applied to traits.

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Big Five Factors

• Introversion vs. extroversion
• Neuroticism or negative emotionality
• Agreeableness
• Conscientiousness
• openness

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Why are genes not everything?

• Not all traits are equally heritable or
  unaffected by shared environments
• Some studies may underestimate the impact of the
  environment
• Even traits that are highly heritable are not
  rigidly fixed and can be modified by experience.