, Solution manual for Life-Span Human
Development, 10th Edition Carol K. Sigelman
Notes
1- The file is chapter after chapter.
2- We have shown you 10 or five pages.
3- The file contains all Appendix and Excel
sheet if it exists.
4- We have all what you need, we make
update at every time. There are many new
editions waiting you.
5- If you think you purchased the wrong file
You can contact us at every time, we can
replace it with true one.
Our email:
, Solution and Answer Guide: Chapter 1: Understanding Lifespan Human Development
Solution and Answer Guide
Sigelman/Rider, Life-Span Human Development 10e, 9780357373651
Chapter 1: Understanding Lifespan Human Development
Table of Contents
Checking Mastery ........................................................................................................................................................... 1
I How Should We Think of Development? ............................................................................................. 1
II What is the Science of Lifespan Development? ................................................................................... 2
III How is Development Studied? ............................................................................................................. 2
IV What Special Challenges Do Development Scientists Face? ................................................................ 3
Checking Mastery
I How Should We Think of Development?
1. What is the difference between an age grade and an age norm?
Answer: An age grade is an age group with certain rights and responsibilities; an age norm is
an expectation about how to behave if you are a certain age.
2. When is the “emerging adulthood” phase of the life span and why has it come into existence?
Answer: Emerging adulthood extends from about age 18 to age 25 or even 29 and was
proposed as a stage of life because the need for advanced education to prepare for more
complex jobs has postponed entry into adult roles.
3. What are two positive messages about old age in the seven themes of the life-span perspective?
Answer: The themes that development is a lifelong process and that there is life-long
plasticity are the most positive themes, but the theme that development is multidirectional
and the theme that it involves gain and loss in every phase imply that old age involves
improvement, not just decline and loss
© 2022 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible
website, in whole or in part. 1
, Solution and Answer Guide: Chapter 1: Understanding Lifespan Human Development
II What is the Science of Lifespan Development?
1. What are the two meanings of discontinuity in development?
Answer: Discontinuity could involve (a) abrupt rather than gradual change, (b) qualitative
rather than quantitative differences (i.e., differences in kind rather than degree), or (c) lack of
carryover of traits from an early period to a later period.
2. What would be an example of a “nature” argument and what would be an example of a “nurture”
argument about why boys are more physically aggressive on average than girls?
Answer: A nature argument might focus on male-female biological differences (e.g., higher
levels of the hormone testosterone in males). A nurture argument might focus on
socialization of boys to compete with other boys and use aggression to gain status in male
peer groups.
3. What are a couple of key differences between how cognitive-developmental theorist Jean Piaget
and learning theorist B. F. Skinner view development?
Answer:
Piaget saw development as stagelike; Skinner saw it as a gradual learning process.
Piaget saw development as leading toward more mature functioning; Skinner believed
development could head in a variety of directions depending on experience.
Piaget saw development as the outcome of an interaction of maturation and experience;
Skinner saw it as the product of experience.
4. What basic question does evolutionary theory raise about development that other theories do
not?
Answer: Evolutionary theorists ask how characteristics and behaviors we commonly observe
in humans today may have evolved—that is, how they may have helped our ancestors adapt
to their environments and survive.
III How is Development Studied?
1. Focusing on the development over childhood of self-esteem, state a research question that
illustrates each of four main goals of the study of life-span development.
Answer: Description: What do children say about their sense of self-worth? Prediction: What
is the relationship between gender and self-esteem? Explanation: What causes gender
differences in self-esteem? Optimization: Can praise boost children's self-esteem?
© 2022 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible
website, in whole or in part. 2
, Solution and Answer Guide: Chapter 1: Understanding Lifespan Human Development
2. Design an experiment to determine whether a college’s arranging for some freshmen to meet and
interact online with their new roommates before they start college helps them get along with
each other better than if they had only met at the start of the school year. Make it clear that your
experiment is really an experiment that has the key features of an experiment and label the
independent and dependent variables.
Answer: Randomly assign a sample of freshmen to two groups to manipulate the
independent variable, pre-college experience with roommate: either a “meet in advance
online” treatment group or a control group receiving no such treatment. Later in the fall,
measure the dependent variable, how well roommates get along with each other. All other
treatment of students in the two groups would be kept the same to achieve experimental
control.
3. You conduct a longitudinal study of the development of self-esteem in college students from age
18 to age 22. What would you be able to learn that you could not learn by conducting a cross-
sectional study of the same topic?
Answer: In a longitudinal study as opposed to cross-sectional study, you would learn about
age changes (not just age differences). You would be able to correlate self-esteem at age 18
with self-esteem at age 22 in the sample to determine whether self-esteem is a consistent
characteristic; you could look at differences between individuals in their trajectories of change
over their college careers; and you could examine relationships between early experiences
with parents or other factors (if you ask about them) and later self-esteem.
IV What Special Challenges Do Development Scientists Face?
1. How many of the characteristics of WEIRD people do you have?
Answer: WEIRD people live in societies that are Western, Educated, Industrialized, Rich, and
Democratic.
2. A researcher deceives research participants into thinking they are in a study of learning when the
real purpose is to determine whether they are willing to inflict harm on people who make learning
errors if told to do so by an authority figure. What ethical responsibilities does this researcher
have? (Yes, this about the famous obedience research conducted by Stanley Milgram, featured in
the recent film The Experimenter.)
Answer: The researcher must debrief the participants afterward about the true purpose of the
study and ensure that they do not leave feeling upset about how they behaved. In this study,
the researcher might also need to be concerned about protection of participants from harm if
some are stressed during the experience or upset afterward.
© 2022 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible
website, in whole or in part. 3
, Solution and Answer Guide: Chapter 2: Genes, Environment, and Development
Solution and Answer Guide
Sigelman/Rider, Life-Span Human Development 10e, 9780357373651
Chapter 2: Genes, Environment, and Development
Table of Contents
Checking Mastery ........................................................................................................................................................... 1
I Evolution and Species Heredity ........................................................................................................... 1
II Individual Heredity............................................................................................................................... 2
III Studying Genetic and Environmental Influences ................................................................................. 2
IV Selected Behavioral Genetic findings .................................................................................................. 3
V Gene-Environment Interplay ............................................................................................................... 3
Checking Mastery
I Evolution and Species Heredity
1. Biological evolution will not necessarily make humans better and better over time, but it will make
them ______________.
Answer: Biological evolution will make humans better adapted to the particular environment
in which they live. (However, genes that are selected by natural selection because they
enhance survival in one environment may prove maladaptive in another.)
2. How are ethology and evolutionary psychology similar in their main goal?
Answer: Both ask how behaviors characteristic of species may have evolved—how they may
have helped earlier members of the species adapt to their environments and consequently
may have become embedded in the genetic endowment of the species.
3. If Ron follows a slow life history track and Don follows a fast life history track from childhood on,
how will their lives be different?
Answer: Ron will likely initiating sexual and romantic relationships and having children until
he is prepared for a career and has the resources to marry and have children, whereas Don
may focus on the present rather than the future, having many relationships and many
children now rather than building toward a future that may be uncertain.
4. Explain why cultural evolution is faster than biological evolution.
Answer: Cultural evolution requires only communicating information from one generation to
the next and sharing innovations along the way, whereas biological evolution must await
natural selection and a gradual increase over many generations in the prevalence of genes
associated with adaptation to the group’s environment.
© 2022 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible
website, in whole or in part. 1
, Solution and Answer Guide: Chapter 2: Genes, Environment, and Development
II Individual Heredity
1. Ted and Ned, fraternal twins, are not very alike at all. Give both a “nature” explanation and a
“nurture” explanation of their differences.
Answer: Nature: By the luck of the draw (which parent chromosomes end up in a particular
zygote), fraternal twins may inherit far less than 50% of the same genes. Nurture: Their
prenatal or postnatal environments could have differed, and these differences in experience
could have affected them either directly or through environmental effects on gene
expression. Examples: One was positioned more favorable in the womb and got more
nourishment, one was favored by parents.
2. Huge nose syndrome (we made it up) is caused by a single dominant gene, H. Using diagrams
such as those in Figure 3.2, figure out the odds that Herb (who has the genotype Hh) and Harriet
(who also has the genotype Hh) will have a child with huge nose syndrome. Now repeat the
exercise, but assume that huge nose syndrome is caused by a recessive gene, h, and that both
parents again have an Hh genotype.
Answer: If the gene is dominant (H), 75% or three of four of the couple’s children would be
expected to have Huge Nose Syndrome (only the child with an hh genotype will not). If the
gene is recessive (h), the couple has only a 25% chance of having a child with the hh
genotype and the syndrome.
3. Juan has red-green color blindness. Knowing that he is color blind, what can you infer about his
parents?
Answer: Red–green color blindness is sex-linked and the recessive gene for it is on the X
chromosome. A boy gets his X from his mother, so Juan’s mother must be a carrier of the
color-blindness gene (but would be color blind herself only if she has a second color
blindness gene). Juan’s father may or may not have the gene (and would be color blind like
Juan if he did).
III Studying Genetic and Environmental Influences
1. What does the following (hypothetical) table of correlations tell you about the contributions of
genes, shared environment, and nonshared environment to frequency of use of marijuana?
Raised together Raised apart
Identical twins +0.70 +0.40
Fraternal twins +0.40 +0.10
Answer: In this example, genes are important because identical twins are more similar in
frequency of marijuana use than fraternal twins; shared environment is important because
both types of twins are more alike when raised together than when raised apart, and
nonshared environment is somewhat important too because we see some dissimilarity
between identical twins raised together (.70 is less than 1.00).
2. What is one problem with adoption studies of genetic influence and one problem with twin
studies?
© 2022 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible
website, in whole or in part. 2
, Solution and Answer Guide: Chapter 2: Genes, Environment, and Development
Answer: Adopted children can be affected not only by their biological parents’ genes but also
by the prenatal environment their biological mother provided before they were adopted
away; they may be placed in homes similar to those they were adopted from; and they are
typically placed in above-average environments (so adoption studies may underestimate the
full effects of good versus bad environments on a trait). Twin studies are limited in that
identical twins typically have more similar prenatal environments than fraternal twins or other
siblings and are likely to be treated alike based on their similar appearance (although studies
suggest that it is their genetic similarity that causes them to be treated alike rather than their
similar treatment that causes them to be psychologically alike).
3. If twin studies show that social anxiety disorder is heritable, what could we learn from molecular
genetics studies of molecular genetics studies of people with and without this disorder?
Answer: Molecular genetics research can help identify which specific genes are responsible
for the findings of twin studies (for example, researchers can scan the genomes of people
with and without social anxiety disorder to see which specific gene variants the socially
anxious individuals often have and the non-socially anxious individuals do not have).
IV Selected Behavioral Genetic findings
1. Rank the following from highest to lowest in heritability: IQ score, weight, religiosity, personality
traits.
Answer: Weight, IQ score, personality traits, religiosity
2. From infancy to late adolescence, the heritability of IQ increases, whereas the contribution of
shared environmental influences to IQ decreases. Why is this?
Answer: As identical twins get older, they seek similar experiences and remain intellectually
similar, but fraternal twins become less similar as they each go their own ways based on their
genetic predispositions. This means that the gap between the correlation for identical twins
and the correlation between fraternal twin pairs enlarges and heritability increases. As twins
spend more time out of the house or move away from home, they have even more freedom
to choose and build environments that suit their predispositions, so shared environmental
influences decrease.
3. Professor Gene Ohm is studying genetic and environmental influences on individual differences in
extraversion/introversion. Based on previous behavioral genetics studies, what should he expect?
Answer: Research suggests that about 40% of the variation among people in major
dimensions of personality like extraversion-introversion will be attributable to genetic
differences, 55% to nonshared environmental influences, and only 5% to shared
environmental influences.
V Gene-Environment Interplay
Label each example below as an example of (a) gene–environment interaction, (b) passive gene
environment correlation, (c) evocative gene–environment correlation, (d) active gene–
environment correlation, or (e) epigenetic effects.
1. Roger inherited genes for artistic creativity from his parents and grew up watching them sketch
and paint.
© 2022 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible
website, in whole or in part. 3
, Solution and Answer Guide: Chapter 2: Genes, Environment, and Development
Answer: passive gene—environment correlation
2. Tamara was abused as a child and this seems to have made her stress response system overly
reactive.
Answer: epigenetic effects
3. Kayla inherited genes for mathematical ability and has been taking extra math and science
courses in college.
Answer: active gene—environment correlation
4. Sydney inherited a gene that can cause intellectual disability but only in children who do not
receive enough folic acid in their diet.
Answer: gene—environment interaction
5. Jorge got genes for anxiety, and his anxious behavior makes his parents overprotective of him.
Answer: evocative gene—environment correlation
© 2022 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible
website, in whole or in part. 4
, Solution and Answer Guide: Chapter 3: Prenatal Development and Birth
Solution and Answer Guide
Sigelman/Rider, Life-Span Human Development 10e, 9780357373651
Chapter 3: Prenatal Development and Birth
Table of Contents
Checking Mastery ........................................................................................................................................................... 1
I Prenatal Development ......................................................................................................................... 1
II The Prenatal Environment and Fetal Programming ............................................................................. 2
III The Perinatal Environment .................................................................................................................. 2
IV The Neonatal Environment ................................................................................................................. 3
Checking Mastery
I Prenatal Development
1. What is conception, and what techniques can be used to assist conception?
Answer: Conception occurs when a single sperm penetrates an ovum (or egg cell), quickly
creating a zygote containing the 46 chromosomes that are the blueprint for that individual’s
life. There are several Assisted Reproductive Technologies (ARTs) that are used to assist
conception. These include drugs to stimulate the release of eggs, artificial insemination, and
in vitro fertilization.
2. How does the development of the brain and nervous system unfold during the embryonic and
fetal periods?
Answer: The brain and nervous system undergo dramatic change during the embryonic and
fetal periods. From the interior of the primitive blastocyst, the ectoderm layer of cells gives
rise to the brain and nervous system. The ectoderm folds into the neural tube and buds
emerge at the top of this tube that will become the brain and the spinal cord emerges from
the bottom of the tube. During the fetal period, neurons proliferate (multiply), migrate, and
differentiate into what they will finally become.
3. When is survival outside the womb possible and what are two factors that influence infant
viability?
Answer: The age of viability is reached at around 23–24 weeks of gestation and is influenced
by many factors including access to excellent healthcare and maturity of the lungs and other
vital organs. Those infants surviving such early arrivals may experience serious health
complications.
© 2022 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible
website, in whole or in part. 1
Development, 10th Edition Carol K. Sigelman
Notes
1- The file is chapter after chapter.
2- We have shown you 10 or five pages.
3- The file contains all Appendix and Excel
sheet if it exists.
4- We have all what you need, we make
update at every time. There are many new
editions waiting you.
5- If you think you purchased the wrong file
You can contact us at every time, we can
replace it with true one.
Our email:
, Solution and Answer Guide: Chapter 1: Understanding Lifespan Human Development
Solution and Answer Guide
Sigelman/Rider, Life-Span Human Development 10e, 9780357373651
Chapter 1: Understanding Lifespan Human Development
Table of Contents
Checking Mastery ........................................................................................................................................................... 1
I How Should We Think of Development? ............................................................................................. 1
II What is the Science of Lifespan Development? ................................................................................... 2
III How is Development Studied? ............................................................................................................. 2
IV What Special Challenges Do Development Scientists Face? ................................................................ 3
Checking Mastery
I How Should We Think of Development?
1. What is the difference between an age grade and an age norm?
Answer: An age grade is an age group with certain rights and responsibilities; an age norm is
an expectation about how to behave if you are a certain age.
2. When is the “emerging adulthood” phase of the life span and why has it come into existence?
Answer: Emerging adulthood extends from about age 18 to age 25 or even 29 and was
proposed as a stage of life because the need for advanced education to prepare for more
complex jobs has postponed entry into adult roles.
3. What are two positive messages about old age in the seven themes of the life-span perspective?
Answer: The themes that development is a lifelong process and that there is life-long
plasticity are the most positive themes, but the theme that development is multidirectional
and the theme that it involves gain and loss in every phase imply that old age involves
improvement, not just decline and loss
© 2022 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible
website, in whole or in part. 1
, Solution and Answer Guide: Chapter 1: Understanding Lifespan Human Development
II What is the Science of Lifespan Development?
1. What are the two meanings of discontinuity in development?
Answer: Discontinuity could involve (a) abrupt rather than gradual change, (b) qualitative
rather than quantitative differences (i.e., differences in kind rather than degree), or (c) lack of
carryover of traits from an early period to a later period.
2. What would be an example of a “nature” argument and what would be an example of a “nurture”
argument about why boys are more physically aggressive on average than girls?
Answer: A nature argument might focus on male-female biological differences (e.g., higher
levels of the hormone testosterone in males). A nurture argument might focus on
socialization of boys to compete with other boys and use aggression to gain status in male
peer groups.
3. What are a couple of key differences between how cognitive-developmental theorist Jean Piaget
and learning theorist B. F. Skinner view development?
Answer:
Piaget saw development as stagelike; Skinner saw it as a gradual learning process.
Piaget saw development as leading toward more mature functioning; Skinner believed
development could head in a variety of directions depending on experience.
Piaget saw development as the outcome of an interaction of maturation and experience;
Skinner saw it as the product of experience.
4. What basic question does evolutionary theory raise about development that other theories do
not?
Answer: Evolutionary theorists ask how characteristics and behaviors we commonly observe
in humans today may have evolved—that is, how they may have helped our ancestors adapt
to their environments and survive.
III How is Development Studied?
1. Focusing on the development over childhood of self-esteem, state a research question that
illustrates each of four main goals of the study of life-span development.
Answer: Description: What do children say about their sense of self-worth? Prediction: What
is the relationship between gender and self-esteem? Explanation: What causes gender
differences in self-esteem? Optimization: Can praise boost children's self-esteem?
© 2022 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible
website, in whole or in part. 2
, Solution and Answer Guide: Chapter 1: Understanding Lifespan Human Development
2. Design an experiment to determine whether a college’s arranging for some freshmen to meet and
interact online with their new roommates before they start college helps them get along with
each other better than if they had only met at the start of the school year. Make it clear that your
experiment is really an experiment that has the key features of an experiment and label the
independent and dependent variables.
Answer: Randomly assign a sample of freshmen to two groups to manipulate the
independent variable, pre-college experience with roommate: either a “meet in advance
online” treatment group or a control group receiving no such treatment. Later in the fall,
measure the dependent variable, how well roommates get along with each other. All other
treatment of students in the two groups would be kept the same to achieve experimental
control.
3. You conduct a longitudinal study of the development of self-esteem in college students from age
18 to age 22. What would you be able to learn that you could not learn by conducting a cross-
sectional study of the same topic?
Answer: In a longitudinal study as opposed to cross-sectional study, you would learn about
age changes (not just age differences). You would be able to correlate self-esteem at age 18
with self-esteem at age 22 in the sample to determine whether self-esteem is a consistent
characteristic; you could look at differences between individuals in their trajectories of change
over their college careers; and you could examine relationships between early experiences
with parents or other factors (if you ask about them) and later self-esteem.
IV What Special Challenges Do Development Scientists Face?
1. How many of the characteristics of WEIRD people do you have?
Answer: WEIRD people live in societies that are Western, Educated, Industrialized, Rich, and
Democratic.
2. A researcher deceives research participants into thinking they are in a study of learning when the
real purpose is to determine whether they are willing to inflict harm on people who make learning
errors if told to do so by an authority figure. What ethical responsibilities does this researcher
have? (Yes, this about the famous obedience research conducted by Stanley Milgram, featured in
the recent film The Experimenter.)
Answer: The researcher must debrief the participants afterward about the true purpose of the
study and ensure that they do not leave feeling upset about how they behaved. In this study,
the researcher might also need to be concerned about protection of participants from harm if
some are stressed during the experience or upset afterward.
© 2022 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible
website, in whole or in part. 3
, Solution and Answer Guide: Chapter 2: Genes, Environment, and Development
Solution and Answer Guide
Sigelman/Rider, Life-Span Human Development 10e, 9780357373651
Chapter 2: Genes, Environment, and Development
Table of Contents
Checking Mastery ........................................................................................................................................................... 1
I Evolution and Species Heredity ........................................................................................................... 1
II Individual Heredity............................................................................................................................... 2
III Studying Genetic and Environmental Influences ................................................................................. 2
IV Selected Behavioral Genetic findings .................................................................................................. 3
V Gene-Environment Interplay ............................................................................................................... 3
Checking Mastery
I Evolution and Species Heredity
1. Biological evolution will not necessarily make humans better and better over time, but it will make
them ______________.
Answer: Biological evolution will make humans better adapted to the particular environment
in which they live. (However, genes that are selected by natural selection because they
enhance survival in one environment may prove maladaptive in another.)
2. How are ethology and evolutionary psychology similar in their main goal?
Answer: Both ask how behaviors characteristic of species may have evolved—how they may
have helped earlier members of the species adapt to their environments and consequently
may have become embedded in the genetic endowment of the species.
3. If Ron follows a slow life history track and Don follows a fast life history track from childhood on,
how will their lives be different?
Answer: Ron will likely initiating sexual and romantic relationships and having children until
he is prepared for a career and has the resources to marry and have children, whereas Don
may focus on the present rather than the future, having many relationships and many
children now rather than building toward a future that may be uncertain.
4. Explain why cultural evolution is faster than biological evolution.
Answer: Cultural evolution requires only communicating information from one generation to
the next and sharing innovations along the way, whereas biological evolution must await
natural selection and a gradual increase over many generations in the prevalence of genes
associated with adaptation to the group’s environment.
© 2022 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible
website, in whole or in part. 1
, Solution and Answer Guide: Chapter 2: Genes, Environment, and Development
II Individual Heredity
1. Ted and Ned, fraternal twins, are not very alike at all. Give both a “nature” explanation and a
“nurture” explanation of their differences.
Answer: Nature: By the luck of the draw (which parent chromosomes end up in a particular
zygote), fraternal twins may inherit far less than 50% of the same genes. Nurture: Their
prenatal or postnatal environments could have differed, and these differences in experience
could have affected them either directly or through environmental effects on gene
expression. Examples: One was positioned more favorable in the womb and got more
nourishment, one was favored by parents.
2. Huge nose syndrome (we made it up) is caused by a single dominant gene, H. Using diagrams
such as those in Figure 3.2, figure out the odds that Herb (who has the genotype Hh) and Harriet
(who also has the genotype Hh) will have a child with huge nose syndrome. Now repeat the
exercise, but assume that huge nose syndrome is caused by a recessive gene, h, and that both
parents again have an Hh genotype.
Answer: If the gene is dominant (H), 75% or three of four of the couple’s children would be
expected to have Huge Nose Syndrome (only the child with an hh genotype will not). If the
gene is recessive (h), the couple has only a 25% chance of having a child with the hh
genotype and the syndrome.
3. Juan has red-green color blindness. Knowing that he is color blind, what can you infer about his
parents?
Answer: Red–green color blindness is sex-linked and the recessive gene for it is on the X
chromosome. A boy gets his X from his mother, so Juan’s mother must be a carrier of the
color-blindness gene (but would be color blind herself only if she has a second color
blindness gene). Juan’s father may or may not have the gene (and would be color blind like
Juan if he did).
III Studying Genetic and Environmental Influences
1. What does the following (hypothetical) table of correlations tell you about the contributions of
genes, shared environment, and nonshared environment to frequency of use of marijuana?
Raised together Raised apart
Identical twins +0.70 +0.40
Fraternal twins +0.40 +0.10
Answer: In this example, genes are important because identical twins are more similar in
frequency of marijuana use than fraternal twins; shared environment is important because
both types of twins are more alike when raised together than when raised apart, and
nonshared environment is somewhat important too because we see some dissimilarity
between identical twins raised together (.70 is less than 1.00).
2. What is one problem with adoption studies of genetic influence and one problem with twin
studies?
© 2022 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible
website, in whole or in part. 2
, Solution and Answer Guide: Chapter 2: Genes, Environment, and Development
Answer: Adopted children can be affected not only by their biological parents’ genes but also
by the prenatal environment their biological mother provided before they were adopted
away; they may be placed in homes similar to those they were adopted from; and they are
typically placed in above-average environments (so adoption studies may underestimate the
full effects of good versus bad environments on a trait). Twin studies are limited in that
identical twins typically have more similar prenatal environments than fraternal twins or other
siblings and are likely to be treated alike based on their similar appearance (although studies
suggest that it is their genetic similarity that causes them to be treated alike rather than their
similar treatment that causes them to be psychologically alike).
3. If twin studies show that social anxiety disorder is heritable, what could we learn from molecular
genetics studies of molecular genetics studies of people with and without this disorder?
Answer: Molecular genetics research can help identify which specific genes are responsible
for the findings of twin studies (for example, researchers can scan the genomes of people
with and without social anxiety disorder to see which specific gene variants the socially
anxious individuals often have and the non-socially anxious individuals do not have).
IV Selected Behavioral Genetic findings
1. Rank the following from highest to lowest in heritability: IQ score, weight, religiosity, personality
traits.
Answer: Weight, IQ score, personality traits, religiosity
2. From infancy to late adolescence, the heritability of IQ increases, whereas the contribution of
shared environmental influences to IQ decreases. Why is this?
Answer: As identical twins get older, they seek similar experiences and remain intellectually
similar, but fraternal twins become less similar as they each go their own ways based on their
genetic predispositions. This means that the gap between the correlation for identical twins
and the correlation between fraternal twin pairs enlarges and heritability increases. As twins
spend more time out of the house or move away from home, they have even more freedom
to choose and build environments that suit their predispositions, so shared environmental
influences decrease.
3. Professor Gene Ohm is studying genetic and environmental influences on individual differences in
extraversion/introversion. Based on previous behavioral genetics studies, what should he expect?
Answer: Research suggests that about 40% of the variation among people in major
dimensions of personality like extraversion-introversion will be attributable to genetic
differences, 55% to nonshared environmental influences, and only 5% to shared
environmental influences.
V Gene-Environment Interplay
Label each example below as an example of (a) gene–environment interaction, (b) passive gene
environment correlation, (c) evocative gene–environment correlation, (d) active gene–
environment correlation, or (e) epigenetic effects.
1. Roger inherited genes for artistic creativity from his parents and grew up watching them sketch
and paint.
© 2022 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible
website, in whole or in part. 3
, Solution and Answer Guide: Chapter 2: Genes, Environment, and Development
Answer: passive gene—environment correlation
2. Tamara was abused as a child and this seems to have made her stress response system overly
reactive.
Answer: epigenetic effects
3. Kayla inherited genes for mathematical ability and has been taking extra math and science
courses in college.
Answer: active gene—environment correlation
4. Sydney inherited a gene that can cause intellectual disability but only in children who do not
receive enough folic acid in their diet.
Answer: gene—environment interaction
5. Jorge got genes for anxiety, and his anxious behavior makes his parents overprotective of him.
Answer: evocative gene—environment correlation
© 2022 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible
website, in whole or in part. 4
, Solution and Answer Guide: Chapter 3: Prenatal Development and Birth
Solution and Answer Guide
Sigelman/Rider, Life-Span Human Development 10e, 9780357373651
Chapter 3: Prenatal Development and Birth
Table of Contents
Checking Mastery ........................................................................................................................................................... 1
I Prenatal Development ......................................................................................................................... 1
II The Prenatal Environment and Fetal Programming ............................................................................. 2
III The Perinatal Environment .................................................................................................................. 2
IV The Neonatal Environment ................................................................................................................. 3
Checking Mastery
I Prenatal Development
1. What is conception, and what techniques can be used to assist conception?
Answer: Conception occurs when a single sperm penetrates an ovum (or egg cell), quickly
creating a zygote containing the 46 chromosomes that are the blueprint for that individual’s
life. There are several Assisted Reproductive Technologies (ARTs) that are used to assist
conception. These include drugs to stimulate the release of eggs, artificial insemination, and
in vitro fertilization.
2. How does the development of the brain and nervous system unfold during the embryonic and
fetal periods?
Answer: The brain and nervous system undergo dramatic change during the embryonic and
fetal periods. From the interior of the primitive blastocyst, the ectoderm layer of cells gives
rise to the brain and nervous system. The ectoderm folds into the neural tube and buds
emerge at the top of this tube that will become the brain and the spinal cord emerges from
the bottom of the tube. During the fetal period, neurons proliferate (multiply), migrate, and
differentiate into what they will finally become.
3. When is survival outside the womb possible and what are two factors that influence infant
viability?
Answer: The age of viability is reached at around 23–24 weeks of gestation and is influenced
by many factors including access to excellent healthcare and maturity of the lungs and other
vital organs. Those infants surviving such early arrivals may experience serious health
complications.
© 2022 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible
website, in whole or in part. 1
