Biology and Behavior
How Children Develop (3rd ed.)
Siegler, DeLoache & Eisenberg
Chapter 3
Overview
 I. Nature and Nurture
 II. Brain Development
 III. The Body: Physical
Growth and Development
I. Nature and Nurture
A. Genetic and Environmental Forces
B. Behavior Genetics
A. Nature and Nurture
 Both heredity and
environment influence
individuals’
characteristics.
 When scientists first bega...
1. Genetic and Environmental Influences
 The interplay between
genes and experience
is very complex.
 This model of
here...
Three Key Elements of the Model
 Genotype: the genetic material an
individual inherits
 Phenotype: the observable expres...
Four Fundamental Relations
1. Parents’ genetic contribution to the
child’s genotype
2. Contributions of the child’s genoty...
Four Fundamental Relations
Parents’
Genotype
Parents’
Genotype
Child’s
Genotype
Child’s
Genotype
Child’s
Environment
Child...
Relation 1: Parents’ and Child’s
Genotypes
 Genetic material is
passed on as
chromosomes—long,
threadlike molecules
made ...
Sex Determination
Sex chromosomes determine an
individual’s sex.
Females have two X chromosomes in the 23rd
pair,
whereas ...
Diversity and Individuality
 Mutations: changes in sections of DNA caused by
random or environmental factors
 Random ass...
Relation 2: Child’s Genotype
and Phenotype
 Although every cell
in your body
contains copies of
all the genes you
receive...
Gene Expression:
Developmental Changes
 Regulator genes largely control the
continuous switching on and off of genes
that...
Gene Expression
About a third of human genes have two
or more different forms, known as alleles.
 The dominant allele is ...
Mendelian Inheritance Patterns
Polygenic Inheritance
 When traits are governed by more than
one gene
 Applies to most traits and behaviors of
interest ...
Relation 3: Child’s
Environment and Phenotype
 As the model indicates, the child’s
observable characteristics result from...
Norm of Reaction
Refers to all the
phenotypes that
could theoretically
result from a given
genotype, in
relation to all th...
PKU
 Children with phenylketonuria (PKU)
—a disorder that is related to a
defective gene on chromosome 12—
are unable to ...
Genetic Transmission of
Diseases and Disorders
 Over 5,000 human diseases and disorders are
presently known to have genet...
Genetic Transmission of
Diseases and Disorders
 Sex-Linked inheritance: male-pattern baldness, red-
green color blindness...
Genetic Transmission of
Diseases and Disorders
 Regulator gene defects: genetic male with female
genitalia
 Unidentified...
The Case of MAOA
 Young men who had
experienced severe
maltreatment were in
general more likely
to engage in
antisocial b...
Parental Contributions to the
Child’s Environment
 A highly salient and
important part of a
child’s environment
is the pa...
Relation 4: Child’s Phenotype
and Environment
 Children are active creators of the
environment in which they live.
 By v...
B. Behavior Genetics
 The science concerned with how
variation in behavior and
development results from the
combination o...
B. Behavior Genetics
 Behavioral geneticists believe that most
traits of interest are multifactorial.
 They are affected...
1. Behavior Genetics Research Designs
 The family study is the mainstay of modern behavior-
genetics research.
 Measure ...
Types of Family Studies
 Twin-Study Designs:
Correlations for pairs of
monozygotic twins on a
trait of interest are
compa...
Family Studies of Intelligence
Identical Twins Reared Apart
 Studied twin siblings who have not
met since they were infants
 The team of investigators ...
2. Heritability
 A statistical estimate of the proportion of the
measured variance on a given trait among
individuals in ...
3. Environmental Effects
 Most obvious source of shared environment is growing up
together in the same family.
 Behavior...
II. Brain Development
A. Structures of the Brain
B. Developmental Processes
C. The Importance of Experience
D. Brain Damag...
A. Structures of the Brain
 Neurons are specialized cells that are
the basic units of the brain’s
information system.
 C...
The Neuron
2. Glial Cells
 Glial cells are the brain’s white matter and
outnumber neurons 10 to 1.
 Cells in the brain that provide...
3. Cerebral Cortex
 Lobes are major areas of the cortex that are
associated with different categories of behavior.
 Occi...
Cerebral Cortex
Cerebral Lateralization
 The cortex is divided into two separate
halves, called cerebral hemispheres,
which communicate t...
B. Developmental Processes
 Question: How does the structure of the
human brain come into being?
 Answer: It is a partne...
1. Neurogenesis and
Neuron Development
 Neurogenesis is the proliferation of neurons
through cell division, is largely co...
Myelination
A fatty sheath of myelin that
forms around some axons in
order to speed and increase
information-processing
ab...
Mapping the Mind
 Techniques used to map the mind and its
workings in children:
 Neuropsychological Approach: examining
...
Electrophysiological Recording
 EEG (electroencephalographic)
recordings of electrical activity
generated by active neuro...
ERP Responses
 These graphs show ERP waveforms in response to novel (red line)
and familiar (yellow line) stimuli.
 The ...
Brain Imaging Techniques
 fMRI (functional magnetic
resonance imaging) uses a
powerful magnet to produce
colorful images ...
2. Synaptogenesis and Synapse Elimination
 Synaptogenesis
 Each neuron forms synapses with thousands of
other neurons, r...
Synapse Production and Elimination
The Adolescent Wave
 Recent research indicates that the
amount of gray matter increases
dramatically in adolescence and
t...
Brain Maturation
The bluer the image, the more mature that part of the cortex is
(i.e., the gray matter has been replaced ...
C. The Importance of Experience
 Plasticity is the capacity of the brain
to be affected by experience.
 Experience plays...
1. Experience-Expectant Processes
 Experience-expectant plasticity is the
process through which the normal wiring of
the ...
Sensitive Periods
 A key element in experience- expectant
plasticity is timing.
 There are a few sensitive periods when
...
Experience-Dependent Processes
 Experience-
dependent plasticity
is the process
through which
neural connections
are crea...
D. Brain Damage and Recovery
Timing and plasticity play
important roles.
 The worst time to suffer brain damage is
when ...
Emergent Effects
of Early Brain Damage
 At 6 years of age, children with congenital brain damage scored
the same as norma...
III. The Body: Physical
Growth and Development
A. Growth and Maturation
B. Nutritional Behavior
A. Growth and Maturation
 Compared with most other species, humans
undergo a prolonged period of physical
growth, which o...
Growth Curves
Variability
 Secular trends are marked changes in physical
development that have occurred over
generations, resulting fro...
Failure-to-thrive (FTT)
 A condition in which infants
become malnourished and fail to
grow for no apparent medical
reason...
B. Nutritional Behavior
 1. Infant Feeding:
Although breast
milk is nutritionally
superior, the
majority of infants
in th...
2. Development of Food Preferences
and Regulation of Eating
 While some food preferences are
innate, experience has a maj...
3. Obesity
 The proportion of U.S. children
who are overweight has
tripled in the past two decades.
 Both genetic and
en...
Overweight—a growing problem
“Fat runs in families”
The overweight children and adults in this painting are all
genetically related, and they are all o...
4. Undernutrition
 Forty percent of the world’s children under
age 5 are undernourished.
 Undernutrition and malnutritio...
Malnutrition and
Cognitive Development
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Biological Foundations

  1. 1. Biology and Behavior How Children Develop (3rd ed.) Siegler, DeLoache & Eisenberg Chapter 3
  2. 2. Overview  I. Nature and Nurture  II. Brain Development  III. The Body: Physical Growth and Development
  3. 3. I. Nature and Nurture A. Genetic and Environmental Forces B. Behavior Genetics
  4. 4. A. Nature and Nurture  Both heredity and environment influence individuals’ characteristics.  When scientists first began to investigate the contributions of heredity and environment, they generally emphasized one factor or the other as the prime influence.  Recent efforts to map the human genome established that individuals differ from one another by only about 1 to1.5% of their genes.
  5. 5. 1. Genetic and Environmental Influences  The interplay between genes and experience is very complex.  This model of hereditary and environmental influences can help to simplify this interplay.
  6. 6. Three Key Elements of the Model  Genotype: the genetic material an individual inherits  Phenotype: the observable expression of the genotype, including body characteristics and behavior  Environment: includes every aspect of the individual, and his or her surroundings, other than genes
  7. 7. Four Fundamental Relations 1. Parents’ genetic contribution to the child’s genotype 2. Contributions of the child’s genotype to his or her own phenotype 3. Contribution of the child’s environment to his or her own phenotype 4. Influence of the child’s phenotype on his or her environment
  8. 8. Four Fundamental Relations Parents’ Genotype Parents’ Genotype Child’s Genotype Child’s Genotype Child’s Environment Child’s Environment Child’s Phenotype Child’s Phenotype
  9. 9. Relation 1: Parents’ and Child’s Genotypes  Genetic material is passed on as chromosomes—long, threadlike molecules made up of DNA  Carry all the biochemical instructions involved in the formation and functioning of an organism  Genes are sections of chromosomes that are the basic units of heredity for all living things Karyotype
  10. 10. Sex Determination Sex chromosomes determine an individual’s sex. Females have two X chromosomes in the 23rd pair, whereas males have an X and a Y chromosome. A gene on the Y chromosome encodes the protein that triggers the formation of the testes, which subsequently produce testosterone, which in turn takes over the molding of maleness.
  11. 11. Diversity and Individuality  Mutations: changes in sections of DNA caused by random or environmental factors  Random assortment: the shuffling of the 23 pairs of chromosomes in the sperm and egg; chance determines which member of the pair goes into the new sperm and egg  Crossing over: the process by which sections of DNA switch from one chromosome to another during meiosis, further increasing genetic variability
  12. 12. Relation 2: Child’s Genotype and Phenotype  Although every cell in your body contains copies of all the genes you received from your parents, only some of those genes are expressed.
  13. 13. Gene Expression: Developmental Changes  Regulator genes largely control the continuous switching on and off of genes that underlie development across the lifespan.  A given gene influences development and behavior only when it is turned on.
  14. 14. Gene Expression About a third of human genes have two or more different forms, known as alleles.  The dominant allele is the form of the gene that is expressed if present.  The recessive allele is not expressed if a dominant allele is present.  A person who inherits two of the same alleles for a trait is described as homozygous.  A person who inherits two different alleles for a trait is described as heterozygous.
  15. 15. Mendelian Inheritance Patterns
  16. 16. Polygenic Inheritance  When traits are governed by more than one gene  Applies to most traits and behaviors of interest to behavioral scientists
  17. 17. Relation 3: Child’s Environment and Phenotype  As the model indicates, the child’s observable characteristics result from the interaction of environmental factors and the child’s genetic makeup.
  18. 18. Norm of Reaction Refers to all the phenotypes that could theoretically result from a given genotype, in relation to all the environments in which it could survive and develop
  19. 19. PKU  Children with phenylketonuria (PKU) —a disorder that is related to a defective gene on chromosome 12— are unable to metabolize phenylalanine.  With early diagnosis and a properly restricted diet, however, mental retardation resulting from PKU can be avoided.
  20. 20. Genetic Transmission of Diseases and Disorders  Over 5,000 human diseases and disorders are presently known to have genetic origins.  Recessive gene: PKU, sickle-cell anemia, Tay-Sachs disease, cystic fibrosis  Single dominant gene: Huntington’s disease, neurofibromatosis  Polygenic inheritance: cancer, heart disease, asthma, psychiatric disorders, behavior disorders
  21. 21. Genetic Transmission of Diseases and Disorders  Sex-Linked inheritance: male-pattern baldness, red- green color blindness, hemophilia, Duchenne muscular distrophy, fragile-X syndrome  Chromosomal anomalies: Down syndrome (trisomy 21), Kleinfelter syndrome (XXY), Turner syndrome (XO)
  22. 22. Genetic Transmission of Diseases and Disorders  Regulator gene defects: genetic male with female genitalia  Unidentified genetic basis: autism spectrum disorder (ASD)
  23. 23. The Case of MAOA  Young men who had experienced severe maltreatment were in general more likely to engage in antisocial behavior than those who had experienced none.  However, the effect was much stronger for those individuals who had a relatively inactive MAOA gene.
  24. 24. Parental Contributions to the Child’s Environment  A highly salient and important part of a child’s environment is the parents’ relationship with the child.
  25. 25. Relation 4: Child’s Phenotype and Environment  Children are active creators of the environment in which they live.  By virtue of their nature and behavior, they evoke certain kinds of responses from others.  They also actively select surroundings and experiences that support their interests, talents, and personality characteristics.
  26. 26. B. Behavior Genetics  The science concerned with how variation in behavior and development results from the combination of genetic and environmental factors  Question: Why are people different from one another?  Answer: Behavioral traits are heritable—influenced by hereditary factors
  27. 27. B. Behavior Genetics  Behavioral geneticists believe that most traits of interest are multifactorial.  They are affected by many environmental factors as well as by many genes.
  28. 28. 1. Behavior Genetics Research Designs  The family study is the mainstay of modern behavior- genetics research.  Measure trait of interest among people who vary in genetic relatedness  Correlations between the measure of the trait in individuals with different relationships are examined to see if they are higher for individuals who:  Are genetically more similar  Share the same environment
  29. 29. Types of Family Studies  Twin-Study Designs: Correlations for pairs of monozygotic twins on a trait of interest are compared to those of dizygotic twins.  Adoption Studies: Researchers examine whether adopted children are more like their biological or their adopted relatives.
  30. 30. Family Studies of Intelligence
  31. 31. Identical Twins Reared Apart  Studied twin siblings who have not met since they were infants  The team of investigators were struck by the similarities they found in traits like IQ, reaction to stress, and traditionalism.  These similarities may be influenced by selective placement and similarities in fostering environments as well as by genetic factors.
  32. 32. 2. Heritability  A statistical estimate of the proportion of the measured variance on a given trait among individuals in a given population that is attributable to genetic differences among those individuals.  Limitations:  They apply only to populations, not to individuals  They apply only to a particular group living at a particular time  They can differ markedly for groups of people who grow up in very different environments  High heritability does not imply immutability  They say nothing about differences between groups
  33. 33. 3. Environmental Effects  Most obvious source of shared environment is growing up together in the same family.  Behavioral geneticists, however, have found surprisingly little effect of shared environment on some aspects of development.  Nonshared environment effects include experiences unique to the individual.  Siblings may have quite different experiences within the same family and their experiences outside the family may diverge sharply.  The primary effect of nonshared environmental factors is to increase the differences among family members.
  34. 34. II. Brain Development A. Structures of the Brain B. Developmental Processes C. The Importance of Experience D. Brain Damage and Recovery
  35. 35. A. Structures of the Brain  Neurons are specialized cells that are the basic units of the brain’s information system.  Cell body: contains the basic biological material that keeps the neuron functioning  Dendrites: receives input from other cells and conducts it toward the cell body  Axon: conducts electrical signals to connections with other neurons  These connections are called synapses
  36. 36. The Neuron
  37. 37. 2. Glial Cells  Glial cells are the brain’s white matter and outnumber neurons 10 to 1.  Cells in the brain that provide a variety of critical supportive functions  For example, glial cells form a myelin sheath around certain axons, providing insulation that increases the speed and efficiency of information transmission.  Play a role in communication within the brain.
  38. 38. 3. Cerebral Cortex  Lobes are major areas of the cortex that are associated with different categories of behavior.  Occipital lobe: primarily associated with processing visual information  Temporal lobe: involved in memory, visual recognition, and the processing of emotion and auditory information  Parietal lobe: governs spatial processing and integrates sensory input with information in memory  Frontal lobe: organizes behavior and is responsible for planning  Information from multiple sensory systems is processed and integrated in the association areas.
  39. 39. Cerebral Cortex
  40. 40. Cerebral Lateralization  The cortex is divided into two separate halves, called cerebral hemispheres, which communicate through a dense tract of fibers, the corpus callosum.  The two hemispheres are specialized for different modes of processing, a phenomenon referred to as cerebral lateralization.
  41. 41. B. Developmental Processes  Question: How does the structure of the human brain come into being?  Answer: It is a partnership between nature and nurture.
  42. 42. 1. Neurogenesis and Neuron Development  Neurogenesis is the proliferation of neurons through cell division, is largely complete by about 18 weeks after conception.  Neurons migrate to their destinations, where they grow and differentiate.  Axons elongate.  Dendrites form spines that increase their capacity to form connections with other neurons.  In the cortex, the most intense period of growth and differentiation occurs after birth.
  43. 43. Myelination A fatty sheath of myelin that forms around some axons in order to speed and increase information-processing abilities.
  44. 44. Mapping the Mind  Techniques used to map the mind and its workings in children:  Neuropsychological Approach: examining effects of brain damage on behavior
  45. 45. Electrophysiological Recording  EEG (electroencephalographic) recordings of electrical activity generated by active neurons  ERPs (event-related potentials) record changes in the brain’s electrical activity in response to the presentation of a particular stimulus.
  46. 46. ERP Responses  These graphs show ERP waveforms in response to novel (red line) and familiar (yellow line) stimuli.  The infants who later recalled how to assemble a toy (left panel) had clearly discriminated between the familiar and novel items on an earlier recognition test.  The infants who did not recall the assembly sequence (right panel) had not discriminated between the components on the earlier test.
  47. 47. Brain Imaging Techniques  fMRI (functional magnetic resonance imaging) uses a powerful magnet to produce colorful images representing cerebral blood flow in different areas of the brain.  PET (positron emission tomography) uses a radioactive material injected into the brain for diagnostic purposes.
  48. 48. 2. Synaptogenesis and Synapse Elimination  Synaptogenesis  Each neuron forms synapses with thousands of other neurons, resulting in the formation of trillions of connections.  Synaptic Pruning  The extensive generation of neurons and synapses results in an overabundance that must be eliminated.  Synaptic pruning occurs at different times in different areas of the brain and is not fully completed until adolescence.
  49. 49. Synapse Production and Elimination
  50. 50. The Adolescent Wave  Recent research indicates that the amount of gray matter increases dramatically in adolescence and then begins to decline.  This second wave of synapse production and pruning may be linked to the impulsive, irrational behavior, which is characteristic of adolescence.
  51. 51. Brain Maturation The bluer the image, the more mature that part of the cortex is (i.e., the gray matter has been replaced with white matter).
  52. 52. C. The Importance of Experience  Plasticity is the capacity of the brain to be affected by experience.  Experience plays a central role in determining which of the brain’s excess synapses will be pruned and which will be maintained.  Synapses that are frequently activated are preserved, a process described as “neural Darwinism.”
  53. 53. 1. Experience-Expectant Processes  Experience-expectant plasticity is the process through which the normal wiring of the brain occurs in part as a result of the kinds of general experiences that every human who inhabits any reasonably normal environment will have.  Is accompanied by vulnerability.  If the expected experience is not available, as in the case of congenital cataracts, development will be impaired.
  54. 54. Sensitive Periods  A key element in experience- expectant plasticity is timing.  There are a few sensitive periods when the human brain is particularly sensitive to particular kinds of external stimuli.
  55. 55. Experience-Dependent Processes  Experience- dependent plasticity is the process through which neural connections are created and reorganized throughout life as a function of an individual’s experience.
  56. 56. D. Brain Damage and Recovery Timing and plasticity play important roles.  The worst time to suffer brain damage is when neurogenesis and neuron migration are occurring (during prenatal development and the first year after birth).  The greatest plasticity is observed when synapse generation and pruning are occurring during early childhood.
  57. 57. Emergent Effects of Early Brain Damage  At 6 years of age, children with congenital brain damage scored the same as normal children.  However, the children with brain damage failed to improve and fell progressively farther behind the normal children, so that by adolescence there were large differences between the two groups.
  58. 58. III. The Body: Physical Growth and Development A. Growth and Maturation B. Nutritional Behavior
  59. 59. A. Growth and Maturation  Compared with most other species, humans undergo a prolonged period of physical growth, which occurs during about 20% of the life span.  Growth is uneven across age, occurring most rapidly during the first 2 years of life and early adolescence.  Growth is also uneven over different parts of the body.
  60. 60. Growth Curves
  61. 61. Variability  Secular trends are marked changes in physical development that have occurred over generations, resulting from environmental changes such as improvement in health and nutrition.  One such change that occurs during puberty, especially among American girls, relates to how an individual perceives and feels about her or his physical appearance, or body image.
  62. 62. Failure-to-thrive (FTT)  A condition in which infants become malnourished and fail to grow for no apparent medical reason.  It is associated with disturbances in mother-child interaction that are thought to stem from characteristics of both child and mother.
  63. 63. B. Nutritional Behavior  1. Infant Feeding: Although breast milk is nutritionally superior, the majority of infants in the United States are exclusively or predominantly formula-fed.
  64. 64. 2. Development of Food Preferences and Regulation of Eating  While some food preferences are innate, experience has a major influence on children’s food preferences and consumption from infancy onwards.  Children whose parents try to control their eating habits tend to be worse at regulating their food intake themselves than children of parents who let their children have more control over their eating.
  65. 65. 3. Obesity  The proportion of U.S. children who are overweight has tripled in the past two decades.  Both genetic and environmental factors contribute to this increase.  Overweight children and teens suffer a variety of social problems.
  66. 66. Overweight—a growing problem
  67. 67. “Fat runs in families” The overweight children and adults in this painting are all genetically related, and they are all overeating.
  68. 68. 4. Undernutrition  Forty percent of the world’s children under age 5 are undernourished.  Undernutrition and malnutrition are almost always associated with poverty.  Malnutrition affects development directly and indirectly by leading children to withdraw from their environments to reduce energy expenditure.
  69. 69. Malnutrition and Cognitive Development

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