PSY 2105

Developmental Science

The field of study that focuses on the range of children's physical, intellectual, social, and emotional developments.

1) To understand the basic biological and cultural processes that account for the remarkable complexity of human development
2) To devise and develop effective methods for supporting and promoting children's health and well-being, and to evaluate these methods

Periods of Development

Periods of time marked by major changes in children's bodies, thought processes, feelings and patterns of interaction, as well as how children are treated

Five broad periods:
1) The prenatal period 2) Infancy
3) Early childhood
4) Middle childhood
5) Adolescence

Domains of Development

social, emotional, cognitive (intellectual), and physical

preformationism

The belief that adultlike capacities, desires, interests, and emotions are present in early childhood

contexts

settings where children live and that influence behavior

nature

The inherited biological predispositions of an individual

Nurture:

The influences exerted on development by an individual's social and
cultural environments and their personal experiences in different environments

plasticity:

The degree to which, and the conditions under which, development isopen to change

Critical:

a specific kind of event must occur for normal development

Sensitive:

a time in development when an experience has an especially profound effect

Developmental stages:

Qualitatively distinctive,coherent patterns of behavior that emerge during thecourse of development

1) Involve qualitative change
2) Marked by simultaneous changes in manydomains
3) Involve rapid change
4) Numerous changes form a coherent pattern

Assessing Individual Differences in Development

Certain developmental traits are highly stable and highly constrained by evolution
Other developmental traits are more easily modified by experience, and it is often these traits that make us different from one another

Culture

Material and symbolic tools thataccumulate through time, are passed onthrough social processes, and provideresources for the developing child

Culture is rooted in everyday activities

Everyday activities are interconnected andorganized over time, forming complexnetworks (or systems) of culture

There is much debate over how to best defineculture, and how human cultural inheritancesmay differ from those of non-human animals

The Tools of Culture

material and symbolic

Material tools:

Focus on physical objects, or on observable patterns of behavior

Symbolic tools:

Focus on abstract knowledge, beliefs, and values affecting development

Mediation:

Organization of the environment through the use of cultural tools

The Processes Involved in Cultural Inheritance

Social Enhancement:
Imitation:
Explicit Instruction:

Social Enhancement:

the most basic social process, children use culturalresources because another person's activity has enhanced the child's immediateenvironment by making these resources available

Imitation:

Children learn to use their cultures resources by observing and copyingthe behaviours of others in their community

Explicit Instruction:

Children are purposefully taught to use the resources of theirculture.

Cumulative cultural evolution:

The ongoing process of cultural change thatis a consequence of variation produced by individuals in the use of culturaltools

Heredity:

Biological, generational transmission of characteristics

Genes:

Basic units of heredity, consist of DNA molecule segments that serve as blueprints

Genotype:

Individual's exact set of inherited genes

Phenotype:

Individual's observable characteristics that result from interaction of genotype with environment

phenotypic variation

It is variations in expressed traits or behaviors that are selected

development of adaptive phenotypes

We inherit genetic tendencies for particular phenotypes that are expressed through an interaction with the environment

Germ cells

sperm and ovum cells in humans

Germ cells contain only 23 pairs of chromosomes

In reproduction the sperm and ovum fuse to form a zygote containing 46 pairedchromosomes (half from the father, half from the mother)

Monozygotic Twins:

one zygote and identical genotypes

Though their genotype is the same, their phenotype is rarely exactly alike due to the influence of subtle variations in their environments

Dizygotic Twins:

two zygotes

No more likely to resemble one another genetically than any other siblings

alleles

Genes that influence a particular trait can have different forms that influence an individual's phenotype

Homozygous:

two inherited genes of the same allelic form

Heterozygous:

two inherited genes of different allelic forms

Gene expression types

1) Dominant and recessive alleles
2) Expressed characteristics could be intermediate between the two alleles (e.g., skin color)
3) Codominance: fully displaying the characteristics associated with each allele (e.g., ABblood type)

Mutation:

An alteration in the molecular structure of an individual's DNA

Mutations occur for a variety of reasons including: errors in chromosome replication, exposure to a number of external agents (e.g., chemicals, radiation), among others

polygenetic inheritance

expression of these traits is influenced by multiple genes

Phenotypic plasticity:

the degree to which the phenotype is open to influence from the environment, rather than determined by the genotype

Some traits (e.g., eye color) have low plasticity and are highly canalized, while others (e.g., intellectual skills) have higher plasticity

Landscape of Phenotypic Development

Conrad Waddington's

Niche construction:

The behaviors, activities and choices of individuals shape the environments (niches) in which they live

E.g., quiet and non-demanding children may received less experiences relevant to the development of social interaction skills, this could influence the child's relationships when they enter school

Ecological inheritance:

Environmental modifications that affect the development of one's offspring

E.g., When people move from one area to another (a new country) they reconstruct the niche in which their children will develop

Organizing Principles for (Prenatal) Development

1) Sequence is fundamental
2) Timing is crucial
3) Development consists of differentiation and integration processes
4) Development proceeds unevenly
5) Development is characterized by changes of organism form and environmental interactions
6) Development is epigenetic

The Periods of Prenatal Development

1.Germinal Period
2.Embryonic Period
3.Fetal Period

Germinal Period

- Begins at conception
- Lasts until the zygote enters the uterus and becomes implanted (8 to 10 days after conception)
- Organism has grown from a single cell to hundreds of cells

Cleavage:

The series of mitotic cell divisions that transform the zygote into the blastocyst

Stem cells:

have the potential to become a variety of different cells (at first totipotent, then multipotent)

Heterochrony:

different parts of the organism develop at different rates

Heterogeneity:

variability in the levels of development of different parts of the organism at a given time.

Embryonic Period

- Begins at implantation (8 to 10 days after conception) and lasts until the end of the 8th week
- By the end of this period
~All major organs have taken primitive shape
~Sexual differentiation has begun
- The placenta allows the exchange of nutrients and waste products between the mother and the embryo.

Development of the Placenta

Early on in the embryonic period the amnion develops to hold the amniotic fluid

Amniotic fluid

protects the organism and provides environment for movement

Placenta:

An organ made up from tissues from both the mother and the fetus that serves as a barrier and filter between their blood streams
- Provides embryo with nutrients and oxygen from the mother's blood
- Transmits embryo's waste products to the mother

Umbilical cord:

A flexible helical structure containing blood vessels that connects the developing organism to the placenta

Ectoderm:

becomes outer surfaces like skin and the central nervous system (brain and spinal cord)

Endoderm:

becomes the digestive system and lungs

Mesoderm:

becomes the muscles, bones and circulatory system

Cephalocaudal pattern:

proceeds from the head down

Proximodistal pattern:

proceeds from the middle of the organism to the periphery

Epigenesis:

The process by which a new phenotypic form emerges through the interactions of the preceding form and its current environment
- For cell differentiation, the environment consists of surrounding cells which exchange information and regulate each other's gene activities
- Cells "know" what to do because surrounding cells "tell" them what to do through the release of signaling proteins

Sexual differentiation

- For the first 6 weeks there are no differences between male and female embryos
~Both have gonadal ridges which will eventually develop into the sex organs
- During the 7th week the gonadal ridges begin to form testes in males, for females the gonadal ridges form ovaries several weeks later
~The development of external genitalia is governed by hormones
~If enough testosterone is present a penis and a scrotum develop, otherwise female genitalia are formed
- Levels of testosterone in the fetal environment may be related to several outcomes after birth:
~Links have been found to slower brain growth prenatally among females, and to sex-typed play in later childhood
~Simon Baron-Cohen and colleagues (Auyeung, et al., 2009) proposed that testosterone exposure during the womb may be related to higher levels of "autistic" traits, though this theory has been critiqued
~ Importantly, these proposed links are correlational and far from clear, they point to potential relationships between aspects of fetal development and childhood behaviour

Fetal Period

- Begins at the 9th week and lasts until birth
- The fetus dramatically grows in weight and length.
- The brain and all organ systems increase in complexity.
- By 15 weeks the fetus exhibits all movements observable at birth.

Some Milestones in Fetal Development

- The intestines have assumed their characteristic position by the 10th week
- At 12 weeks, external sexual characteristics are often (not always) clearly visible
- At 16 weeks the head is upright, the limbs are well developed, and the ears have migrated to their proper position
- At 5 months almost all the nerve cells have developed
- At 7 months the age of viability is reached, the lungs are capable of breathing air and the eyes can open and respond to light.
- In the 8th and 9th months the brain becomes more and more wrinkled and in the last few weeks before birth the infant doubles in weight

Touch:

the fetus begins to respond to touch from itself and the umbilical cord as early as 8 weeks

Motion:

the vestibular system begins functioning at 5 months

Sight:

After 26 weeks the fetus has been found to respond to light with changes in heart rate and movement

Hearing:

The fetus has been found to respond to sounds at 5 to 6 months and to recognize changes in sound by 6 and 7 months

Fetal Movement

- By the end of the 4th month mothers can usually feel their baby moving around
- Ultrasounds have suggested that fetal movement often begins 8 weeks after pregnancy
- Research suggest that fetal movement may play a significant role in later development
- For example, studies on chick embryos (baby chickens) have found that limiting fetal movement may influence nerve development in their limbs
- Some researchers suggest fetal movements may play a similar role in humans

Dynamic systems theory:

explains how complex systems of behavior emerge from the interaction of less complex parts

Teratogens:

Environmental agents that can cause deviations from normal development and can lead to abnormalities or death.

Six general principles of the effects of teratogens:

1.The susceptibility of the organism depends on its developmental stage.
2.A teratogen's effects are likely to be specific to a particular organ.
3.Individual organisms vary in their susceptibility to teratogens.
4.The mother's physiological state influences susceptibility to teratogens.
5.The greater the concentration of a teratogenic agent, the greater the risk.
6.Teratogens that have little or no effect on the mother can seriously affect the developing organism

Prescription drugs

- Used by between 65 and 94 percent of women during pregnancy
- Some drugs (e.g., thalidomide) have been found to cause abnormalities

Tobacco

Maternal use related to an increased rate of spontaneous abortion, stillbirth, and neonatal death; as well as birth defects and lower birth weight

Alcohol

- Fetal alcohol spectrum disorder (FASD)
- Fetal alcohol syndrome (FAS)

Marijuana

- Most commonly used drug among pregnant women
- No causal links to use have been demonstrated, some concern about effects on placenta growth and effects on development

Cocaine

- Babies of cocaine-addicted mothers are at risk for variety of problems
- Residual effects to exposure may be long term
- Effects of prenatal exposure may be compounded by other maternal circumstances

Methamphetamine

- Common among illicit drugs used during pregnancy
- Significant incidence of deficient fetal growth and small fetal size

Heroin and methadone

- Addicted mothers give birth to addicted babies
- Increased risk of being premature, underweight, and vulnerable to respiratory illness

The Stages of Labor

- Normally begins approximately 266 days after conception
- Proceeds through three stage
1) Uterine contractions cause the cervix to dilate
2) The baby is pushed through birth canal
3) The baby is delivered, and the afterbirth is delivered

differentiation

new skills

integration

these skills are organized and coordinated

Early infancy

- In about 12 weeks infants
~Gain about 6 pounds (2.7 kilograms)
~Grow more than 4 inches (10 centimeters)
~Have a rapidly expanding head circumference

- Growth of the skull
~Fontanels allows molding of the skull during birth
~Developing brain pushes against the skull
~Head circumference expands

Brain at birth

- Contains most of the neurons it will ever have (about 100 billion neurons)
- Will grow about four times larger by adulthood
- Most of the growth in the size of the brain happens in the first few years after birth

Synaptogenesis

The process of synapse formation

myelination

insulates axons and speeds transmission of impulses

synaptic pruning

- use it or lose it
- The selective dying off of non-functional synapses

Grey Matter

- dendrites and axons
- increases when dendrites develop new branches and axons grow longer.
- This leads to the formation of new synapses

White matter

- myelin sheath coat more axons allowing neural signals to be sent faster

Experience-expectant processes

- Anticipate experiences that are universal in normally developing infants
- Examples: the visual cortex prepares infants for certain types of visual experiences, language development
- Allows infants to take advantage of certain features of the environment and develop basic abilities

Experience-dependent processes

- Initiated in response to specific experiences of individuals
- Example: Research on rats in enriched environments
- Allows individuals to take advantage of and learn from changing information in the environment

exuberant synaptogenesis

there are far more synapses present than those required by particular experiences

infant sensory development

1) Infant perception begins with total confusion and becomes ordered with experience and insight about environment
2) Infants lose innate abilities to detect certain sensory features that do not fit in their environment through perceptual narrowing
- Perceptual narrowing: a process in which infants lose their apparently innate abilities to detect certain sensory features because those features do not occur very often in their environments.
3) Biology plays a critical role by endowing infants with special abilities to interact with environments

Methods for Studying Infant Sensory Capacities

- Overt behavioral or physiological responses
- Electroencephalography (EEG)
- Visual preference technique
- Habituation and dishabituation
- Interview with Judy DeLoache

Infant Hearing

- Fetuses respond to sounds outside womb, and newborns respond to sound immediately after birth
- Newborn infants distinguish and prefer the sound of a human voice
- Newborn infants are attuned to language sounds, especially infant-directed speech

- 2-month-olds can perceive distinctions in phonemes used in all the world's languages
- By about 6 to 8 months of age, infants only perceive the sounds made in the language(s) they hear
- This is an example of perceptual narrowing
Research on infants growing up in bilingual environments suggests these babies may remain sensitive to nonnative phonemic contrasts for a longer period of time than do babies in monolingual environments

Infant Vision

- All the anatomical visual system components are present at birth, but they are not fully developed
- Infants' vision is blurry and their eyes cannot form clear composite images
- Infants' visual acuity increases dramatically over the first few months of life.
- By the age of 4 months, a baby can see nearly as distinctly as an adult.

Perceiving Patterns and Faces

- Slightly blurred, slight double vision at birth
- Infants' can see best for things directly in front of them (like mothers' face)
- Evidence of colour vision by 2 months of age
- Newborn infants have the ability to distinguish patterned stimuli from plain
- Infants' show preferences for moving, facelike stimuli

Becoming Coordinated with the Social World

- This coordination involves adjustments from both infants and caregivers
~Reflexes involve infants reacting to the external world
~Through experience reflexes become organized into more complex behaviours allowing infants to more effectively interact with the world
~Responsive caregiving is necessary for infants to survive
~Infants' developing behavioural organization and abilities to coordinate their own actions with those of caregivers influences their early relationships

Sleep Patterns of Infants And Coordination with Caregivers

- newborn babies sleep approximately 16 ½ hours a day in the first week of life and this gradually decreases
- Newborn sleep patterns do not correspond to the day/night sleep cycle originally and must be coordinated with adult patterns
- This is a source of stress for both parents and children

- Cross-cultural studies have documented many differences in how parents and children coordinate their sleep patterns
~Sleep patterns are often a response to very different ecologies, and are based on cultural beliefs and values regarding children

Moral Principles "Constraining" Sleeping Arrangements

- The principle of "Incest Avoidance"
~Likely universal
- Moral Principles in India relevant to sleeping arrangements
~"Female Chastity": it is important for young unmarried girls to be chaperoned
~"Respect for Hierarchy": social hierarchy is expressed with deference and distance
~"Protection of the Vulnerable": children are highly valued and should not sleep alone
- Moral Principles in the United States relevant to sleeping arrangements
~"Autonomy": highly valued, children should be encouraged to be self-reliant
~"The Sacred Couple": co-habituating adults should sleep together and alone

Temperament

describes individual modes of responding to environment that appear to be consistent across situations and stable over time

Temperament: Chess and Thomas's approach

- Proposed nine key traits of temperament
- These can be organized into three broad temperament categories: 1) easy, 2) difficult, and 3) slow to warm up