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Chapter 3 : Human Development
Transcript of Chapter 3 : Human Development
Genotypes & Phenotypes
: physical characteristics that are observable (e.g. hair and eye color, height, skin tone, etc.)
: genetic information in our DNA that determines phenotypical information. Biological influence on phenotypes
Phenotypes are also influenced by environmental factors (exposure to pollution can cause asthma, certain diets influence development, etc)
the 22 pairs of chromosomes that are
sex chromosomes--responsible for all development of a person except biological sex.
Sex Chromosomes :
the final, 23rd pair of chromosomes. XX = Female, XY = Male
sex cells (sperm and ovum combined) that create sex chromosomes. Gametes are created through meiosis.
the process by which gametes are formed. It reduces the number of chromosomes present in half (46 to 23 pairs)
XX - Female
XY - Male
XXY - Klinefelter Syndrome
XO - Turner Syndrome
(Diamond, 1994; Fausto-Sterling, 2007)
Most chromosomal mutations occur during meiosis when duplicates are being formed.
Mutations typically cover multiple genes instead of one specific marker (like originally believed)
: most common type of chromosomal mutation, occurs in 1 out of every 1,000 live births.
Trisomy X :
how Down Syndrome develops. The person has 3 (X) chromosomes instead of 2 in the 21 pair.
Influence of Heredity on Behavior
Science is not advanced enough to determine 40% of your behavior comes from the environment and 60% comes from your DNA.
Many researchers argue that we will never be able to separate the two factors and determine their unique contributions
examining a whole population to examine individual differences that are influenced by genetic factors (e.g., why some people are more intelligent than their neighbor)
Kinship Studies :
the opposite of heritability estimates, in Kinship Studies we only research people that are related by biological DNA.
Adopted children's intelligence scores resemble their biological parents more than adopted parents
Personality is less influenced by heredity than intelligence (.40-.50 correlation for identical twins on personality measure).
Schizophrenia has a very high correlation rate between identical twins (r = .90)
Environmental Influences on Behavior
Environmental researchers argue and question the reliability of hereditary estimates.
People in the same environment will display similar characteristics.
It is important to study people from
to acknowledge environmental influences
Think of the classic stories of identical twins raised in different environments, most of the time they
still display very similar characteristics.
Environmental researchers also argue that genetic perspectives have lead to faulty, racist based "findings"
Researchers also state that the two factors will always influence each other. People with "intelligent genes" cannot develop to their full potential in non-stimulating environments. People with lower IQ can become "smarter" if they are exposed to intellectual resources.
The research is still overwhelmingly inconclusive (i.e. more research is needed!)
a person's unique, genetically determined response to the environment. People develop differently depending on their level of stimulation in the environment combined with their genetic predispositions.
the concept that certain human characteristics follow very strict paths of development creating only one or two outcomes. The environment must provide extremely harsh conditions to cause canalized traits to not develop.
Most canalized traits are believed to be traits that are essential to survival.
Genetic - Environmental Correlation :
the statement that our genes influence and predict the environments that we expose ourselves to.
Passive Correlation :
in this case the child has little control over the environment that their parents expose them to.
the child's disposition exposes them to specific developmental influences based on their personality.
Active Correlation/Niche-Picking :
the last stage of genetic - environmental correlations where the person picks environments that suit their genetic dispositions. Commonly starts in late junior high and high school.
Many factors can influence problems during fetal development
disorders that develop in the womb that are not due to inheritance of genes (e.g., exposure to radiation, pregnant mother with STDs or drug addiction, etc).
Any substance or stimuli that is harmful to the development of fetal development.
Drug and alcohol addictions are one of the most common teratogens in the United States
Fetal Alcohol Syndrome :
Congential disorder where children have lower birth rates, a smaller head, physical abnormalities, and emotional disorders.
Tobacco exposure while in the womb is harmful to development. Children of smoking mothers have lower birth rates, higher rates of infant mortality, higher rates of asthma, and lower intelligence scores.
Critical and Sensitive Periods
time frame in development where an organism is ready to learn a new skill but must be exposed to environmental stimulation or they will not learn the skill
If the skill is not learned within a specific time, the skill will never be acquired.
less restrictive than a critical period. Development is most efficient during the sensitive period, but can still occur before or after (but is usually harder to develop)
Sensitive periods are more common for humans than critical periods. Toilet training is a common example for sensitive periods.
Bowlby’s attachment studies are a classic example of sensitive periods in humans.
Is it better to develop early or late?
Research shows it depends on the developing process, but typically it is easier to develop later than earlier.
The most common examples of critical periods in humans are deprivation of visual stimulation and language deprivation.
Deprivation and Development
Children growing up in poverty stricken areas experience negative developmental influences (e.g., poor nutrition, pollution/unsafe housing, gangs, violent crime, etc.)
Educational quality is significantly lower for Inner City children than it is for other children.
Experimental research demonstrated that living in high poverty areas is detrimental to physical and psychological health as well as school success compared to children who out of poverty (Goering, 2003; Leventhal & Brooks-Gunn, 2003).
Parents in lower SES are also likely to have more children than people in high SES.
Parents of lower SES often center their parenting styles around children following orders, staying out of trouble, and physical punishment.
Children make up 19% of poverty in America.
Children in poverty typically experience lifelong physical problems, cognitive deficiencies, mental illnesses, and antisocial behavior.
the process by which an environment is stimulating, safe, loving, and promotes intellectual learning.
Parents of high SES develop more hands on approach (reading, spending time together, sharing experiences) and allow their children "freedom to grow"
Babies should be bombarded with sensory information (expose them to colors, sounds, things to touch, etc). This is how they learn!
There is a believed correlation between social interactions as an infant and "social skills" as one ages.
Children form abstract thinking faster when they are given the chance to view themselves in the mirror often
"It is wise to view all of childhood as a
relatively sensitive period
" Coon & Mitterer, pg. 103, 2012.
term used to define newborn infants less than six months old
Infants are born with certain instinctual reflexes, they are :
Motor Development for Infants
Children follow a structured path of motor development
Time of start for motor development varies, but the stages are almost always in order (e.g., infants crawl before walking and walk before running).
The process is so structured due to biological and muscular development in the human body
muscular development follows the directional pattern of head to toe.
refers to that muscular development also extends from the center of the body to the extremities.
Children require time to "master" a motor development skill after their initially learn it
Emotional attachments are the close bonds that infants form with their caregivers
The quality of this attachment drastically influences the infant forming healthy relationships for the rest of their life.
The Harlow Monkey studies experimentally verified that close physical contact influences psychological health.
Animals need interaction too!
Harlow Monkey Study (1962) :
Baby monkeys were raised without mothers.
They had two "mother figures": a wire mommy that held their milk bottle and a second mommy who was made of warm terrycloth.
When stressed or scared by audio clips of dogs barking, the infant monkeys always ran to the terrycloth mother. In other words, physical contact increased a bond, not feeding.
Unfortunately, all monkeys raised without a mother were not able to transition to life with other monkeys. They lacked the social development to succeed in the monkey hierarchy.
Monkeys who were introduced to the social group before six months adapted---monkeys introduced after six months could not.
Again, this reinforces critical development periods.
Contact comfort :
reassuring physical touch from caregiver that is very important during the first year of development
Separation Anxiety :
common for children, but too much contact comfort will cause a child to be hypersensitive to separation (separation anxiety disorder)
It is easy to treat too much affection, sometimes it is impossible to reverse damage from too little affection
Periods of Development
the cellular process by which DNA duplicates itself. An ongoing process throughout development. A key element being the DNA is an exact copy of it's "parent"
Complementary Base Pairing:
DNA's "ladder structure" is composed of
four base pairs
in humans. This aspect is what makes us highly unique to other organisms. The process by which the pairs form is called complementary base pairing.
Reproductive Medical Technology
Genetic counseling :
the medical process by which geneticists assist prospective parents in determining if the benefits outweigh the risks if one parent has a inheritable disease.
Ethical problem with designer babies?
Prenatal diagnostic methods :
procedures used by medical doctors to determine if problems are occurring while in the womb.
Anatomy of a human
From larger to smaller we have : cells, nucleus, and chromosomes.
contain our unique genetic information. Most humans have 23 pairs of chromosomes. Chromosomes are found in the nucleus of cells.
a chemical substance located inside chromosomes. Shaped like a "ladder", referred to as a double helix. Each connection serves as a genetic instruction for development
specific segments of DNA. We have an estimated 25,000 genes.
Both dogs and rats have more genes than humans. Rats have about 3 times more genes than humans.
99.5% of human genes are identical regardless of who you examine (e.g., sex, race, nationality).
Humans and chimpanzees share 98% of the same genes.
All mammals are at least 90% genetically identical to humans.
Identical twins are the only humans that share 100% identical genes.
Children receive pairs of identical genes from each of their parents (this is often referred to as "crossing over") .
The identical genes will appear on the place (marker) on their corresponding chromosome.
identical genes that the offspring receives from both parent.
the alleles from both parents are identical (both hair genes are blonde).
the alleles from both parents differ, one gene will dominate the other (brown hair outweighing blonde hair)
: an allele that determines the offspring's characteristic. Viewed as the "active" allele. Referred to as "
" in genetic research.
the allele that has no influence or effect. Is always "submissive" to the dominant allele. Referred to as "
" in genetic research.
Dominant alleles always win out
--the only instance a recessive trait is passed on is when there is a homozygous pairing of two recessive (
) alleles. An example is blond hair.
sometimes people carry a recessive gene and do not experience the trait. They still could potentially pass on the gene to their offspring (e.g., hemophilia, sickle cell anemia, Tay-Sachs disease, etc.)
Imprinting and Mutation
the process by which the dominant-recessive inheritance pattern is not followed. Usually attributed to negative development (e.g., fragile x syndrome)
Imprinting usually only lasts one generation
a sudden change or development in a segment (gene) of DNA.
Mutations occur by chance or environmental exposure (e.g., radiation, chemicals like asbestos or mercury, etc.) Mutations are either
Polygenic Inhertiance :
the process of multiple different genes influencing development
Examples of polygenic inhertiance are eye color, height, weight, intelligence, and personality.
A newer area of study in genetic research
There are more questions than answers when it comes to polygenic inheritance
With the 43 chromosomes, there are 8,388,608 variations that could occur.
a chemical process that surrounds DNA and RNA but is not directly attached to the genes. After the chromosomes are formed exposure to methylation causes the genes to alter. This was discovered by chemists in 2013.
DNA that geneticists believe have no use OR we simply have no idea what the purpose is.
Genetic diversity is often discussed in relation to mutations. Low genetic diversity in an ecosystem tends to cause lower rates of survival.
High rates of mutations are more common in ecosystems with higher amounts of genetic diversity.
By the 1930s researchers already knew children in orphanages reported lower IQ scores than children reared by parents.
They created an experiment to test the effects of nurturing and socialization. Twelve infants that lived in an orphanage were observed (control) and thirteen infants were placed in a mental institution for women with intellectual disabilities. The women were aged 18-50, but had mental ages ranging from 5-12.
Further explaining the level of interaction: infants in the orphanage received little individual attention whereas the infants in the wards were doted upon all the time (Skeels, 1966).
Two years later the researchers found that children in the mental institution who
received attention gained 28 IQ points
but children in the orphanage who
received no attention lost 30 IQ points!
Follow-up testing 21 years later revealed that the children who received attention in the mental institution were more successful in life compared to the children who grew up in the orphanage.
Similar results were found in Indian orphanages (Taneja et al., 2002).
Failure to Thrive :
a concept used to explain that emotionally neglected children typically do not physically develop.
Absence of Attachment
Infants who do not develop a deep attachment with a caregiver experience a loss in weight, excessive crying, and withdrawal from the environment (fetal position)
Additional infant studies have found that with adopted children attachments can form as late as six years of age.
Children who formed attachments at later ages displayed antisocial behaviors such as : excessive need to be around caregiver, trusting of strangers, and lower amounts of friendships.
The previously mentioned Romanian orphanage studies found that attachment problems extend into later childhood. These features included cognitive impairments, peer rejection, inattention, and hyperactivity.
Neurological studies find that children without caregiver attachments have different brain waves.
Quality of Caregiving
Sensitive Caregiving :
a parent that responds to their child's needs with the three factors in mind : timing, consistency, and with physical contact.
The mom who views infant care as a "chore", rolls her eyes, and expresses negative mannerisms is the exact opposite of sensitive caregiving.
As previously discussed, SES plays a role in parenting styles.
Interactional Synchrony :
The process of caregivers and infants expressing positive emotional expressions. It helps the child develop and regulate emotional responses.
Insecurely attached children often have parents who overstimulate their child instead of participating in interactional synchrony.
Children who experience abuse or maltreatment are much more likely to display disorganized or insecure attachment styles.
Mothers under extreme duress often have children who display similar insecure attachment styles
It is important to remember that attachment styles are completely social constructs, there is no relation between attachment styles and heredity (that we know of)
Fathers and Caregiving
There is a gendered difference (this does not mean it is biological) in many countries on how fathers and mothers interact with their children.
Mothers are typically given the dirty work (literally) while being responsible for their children's physical and emotional needs.
Fathers focus more on being a "buddy" to their children and promote physical interactions.
Fathers are most likely to engage in physical play with the child. This play is helpful in child development. It is believed to increase spatial understanding and increase confidence in the world.
As gender egalitarian beliefs have increased in America, there is a less gendered divide in specific behaviors (i.e., fathers will now change diapers and mothers will engage in physical interactions with the child).
Studies show that stay @ home fathers kick ass! They are typically not influenced by gendered beliefs and display both parental styles to their children.
Fathers with highly gendered beliefs (e.g., the father who believes the wife's place is at home) typically spend less time with their children than fathers who have less strict gendered beliefs.
Just like maternal caregiving, paternal caregiving is highly influenced by their marriage/relationship stability.
The more information an infant focuses on, the quicker the infants processes information.
After infants are exposed to novel stimulation, they often experience sensory overload and take a couple of minutes to recover.
We also know that it is hard for infants to remove their attention once focused.
The cerebral cortex (still developing in children) is responsible for shifting your focus of attention.
Sustained Attention :
the ability to hold attention increases as one ages (positive correlation)
It is argued sustained attention develops as tasks become more complex and require more time.
The process that we go through to learn what is acceptable and punishable in our society. It helps us gain abilities to successfully navigate our social world.
One of the strongest socialization processes in all cultures is gender socialization
Thoughts on the different parental treatment of boy and girl infants?
Childhood socialization is often centered around if children work or do not work in a particular society.
The children who work are often treated like adults compared to children who do not work at early ages
Do parents "regress" to childhood states to deal with children?
A personal "description" of how masculine or feminine a person is
in relation to their culture.
Typically, gender identity matches a person's biological sex.
specific roles or tasks that are assigned to people based on their biological sex. These gender roles are not hardwired into us, we learn them through socialization.
Some gender roles change according to the culture (e.g., fathers), but other roles are almost universal (aggressiveness and masculinity).
Not innate in children (Biernet, 1991)
Most common attributes for men:
adventurous, independent, stoicism, and sexual prowess
. For women:
sentimental, submissive, helpless, and dependent.
Biological Determinism :
the idea that males and females are born different. This argument states our biology (read : genes and cellular makeup) make men and women drastically different.
Differential Socialization :
the opposite of biological determinism. Differential Socialization is the argument that men and women are taught to act differently.
Socialization of Emotions
Research shows that the basic universal emotions are: Happiness, Sadness, Disgust, Anger, Fear, and Surprise.
Even blind people who have never seen facial expressions display these basic emotions (Matsumoto & Willingham, 2009)
Unlike facial expressions, body language has more variability between the cultures (Henslin, 2013).
Complex emotions are combinations of basic emotions (e.g., Anger + Fear = Jealousy; Anger + Disgust = Aggression; Sadness + Fear = Depression).
Even after being locked in her bedroom for a decade, Genie still knew how to use basic emotional expressions.
Psychological studies show that emotions are suggestive and "contagious".
The Influence of Birthweight
Low birthweight (LBW):
born under 5.5lbs. Around 22 million children are born low birthweight according to UNICEF.
Very low birthweight (VLBW):
under 3.5lbs at birth.
Extremely low birthweight (ELBW):
under 2 pounds, 3 ounces. There is a 50% survival rate for children classified as extremely low birthweight.
The previous classifications are most commonly associated with preterm births.
Small for gestational age (SGA):
infants born full term but are still small
There are many causes for low birthweight and most of them actually occur simultaneously. The following factors influence low birthweight: maternal illness during pregnancy, malnutrition, underweight mother, younger age (very noticeable pre-16), pollution, absent fathers, and smoking.
25% OF ALL LOW BIRTHWEIGHT CHILDREN IN AMERICA ARE INFLUENCED BY TOBACCO EXPOSURE.
Protective factors of negative effects:
mother's education, household income, and family support.
There is a correlation between adult diabetes and heart disease with low birthweight at infancy.
12% of Mississippi children are born classified as low birthweight. This is the highest in the country.
A person physically develops in the first two years more than any other period of life.
Infants grow 50% greater than their birth size in the first year
By the end of the second year, toddlers are almost 3 feet tall. That's a 75% increase when compared to birth weight!
Infants double their weight in the first 5 months! Average weight for a one year old child is around 22 pounds.
By the second year, infants are four times the size of their birth weight. The average weight being around 30 pounds.
Growth is not periodic (timed) and actually occurs in "spurts"
Baby fat in the first year is normal and helps the infant maintain body temperature
Childhood obesity rates have almost tripled in America over the past decade http://www.cdc.gov/healthyyouth/obesity/facts.htm
Muscle development is almost non-existent in childhood development. This occurs the most during puberty.
Breast VS. Bottle
Infants require more energy than adults due to their rapid growth. Therefore, proper nutrition is paramount in growing children.
The ongoing debate of breast feeding or formula has pretty much ended with a victor (very rare in science!)
Breast feeding is highly beneficial for multiple reasons :
Higher levels of nutrients (assuming the mother is healthy!)
Breast fed children grow faster than formula babies
Breast milk contains antibodies that improve the infants immune system
Less stomach problems (change a diaper between the two and you will notice a difference!)
Prevents tooth decay and jaw abnormalities that occur due to using a bottle excessively.
Perfect way to form secure mother/infant attachment
In developing countries, infants breast feeding are the healthiest children.
Given lacking resources, once children are weaned they experience malnutrition in many developing countries.
1/3 of the world's children suffer from malnutrition.
across the board malnutrition resulting from a complete lack in nutrients.
malnourishment most commonly shown in commercials. Distended stomach due to a
lack of protein in diet.
These two diseases cause lifelong developmental problems for physical and intellectual traits.
Lots of protein in a diet-note the tummy differences
Research about Down Syndrome
very rare outcome where the part of a chromosome attaches to the wrong chromosome.
For people with Down Syndrome, the part of the 21st chromosome that doesn't develop properly attaches to a random chromosome.
rarest way Down Syndrome develops. In this outcome, the chromosomes appear to have multiple deficits instead of focused on just the 21st chromosome.
People with mosaic pattern mutations appear to have the least severe symptoms of Down Syndrome.
Common harmful symptoms associated with down syndrome:
mental retardation, memory and speech deficits, increased risk of cancer and Alzheimers, and a lower life expectancy.
In the early 1900s, most people with Down Syndrome did not live to their 30s. Today, many are living into their 60s.
The risk of a woman having a child with down syndrome increases as she ages (
this is only half of the study though!!
Men over the age of 45 are more likely to father children who have down syndrome (why does this part of the study never get mentioned??)
Obviously, one of the major determinants of success for a child with Down Syndrome is the quality of parenting from the family.