Development 1

• What is developmental psychology?

  Development, Evolution, Neuroscience

• what is the role of genes and environment in development?

• What traits do we study?

• What is the impact on development?

• How do you measure it?

Maturation: the biologically timed unfolding of changes within the individual according to their genetic plan.

e.g. in the right environment, a baby’s genetic plan will create a maturation timeline where it gets his baby teeth at 5 months, walks at 8 months, etc.

Learning: permanent changes in our thoughts, behavior, and feelings due to experiences. learning processes store information through neural connections that guide your response to stimuli.

interactions perspective

most of developmental changes reflect the interaction of maturation and learning.

e.g. you won’t learn to walk until muscles and limbs mature enough to support walking.

e.g. in the same way, learning affects maturation. a child is given proper nutrition but isolated in a dark room. the kid does not learn from input from the outside world and will not mature and get proper speech vision, etc.

Marshmallow test

• the kid can wait to get two marshmallows or eat the one in front of them now

• then they’re grouped into high/ low-restraint

• it reflects self-regulation and is correlated to adulthood

• high restraint have better more successful lives.

How do you ask babies questions?

Habituation procedure:

• Infant sensory interactions with the environment

• detecting the difference between two stimuli

• presents a stimulus repeatedly and measures changes in physiological changes like heartbeat or eye movement

• a new stimuli will provoke a burst of activity until the infant goes back to baseline levels when it is repeated (gets habituated to the stimulus)

• the stimulus is changed and if the baby recognizes it and has a burst of physiological responses displaying dishabituation

• e.g. eye tracking for babies looking at a face

• can the baby tell if the stimulus has changed?

Event-related potentials (ERP)

• Infant sensory interactions with the environment

• a special cap with an array of electrodes is placed on the baby and decent changes in electrical activity in neurons

• the behavior being measured triggers changes in different parts of the brain

• e.g. visual would trigger occipital lobe

• how does the brain react to stimulus?

High amplitude sucking method

• measure baseline sucking rate

• baby is given control over the stimulus

• e.g. if the baby sucks faster it triggers more music to be played and if they like the music they suck more if they don’t they suck slower

• does the baby like the stimulus?

Preference method

• uses a looking chamber with two different stimuli and measures the time and direction the baby is looking

• have to make sure the baby can tell the stimuli apart

• which stimuli does the baby like more?

Limitations

• e.g. babies have to be a certain age because sometimes babies can’t see meaning they cannot complete a task. but if babies grow up (e.g. 4 months) they get used to and rewarded for looking at faces so they would prefer faces.

Nature vs. Nurture

• behaviors are complex and driven by both processes

• e.g. a person can be susceptible to schizophrenia due to genetics but environmental factors like stress trigger it. even age can be added as a factor.

Role of genes and environment on development

• newborn babies were shown two images with one that looked like a face and one not. the babies look at the one similar to faces. (genes only not behaviour)

• phoneme sensitivity changes based on age and environment (young infants, 10 month olds and Hindi adults can recognize the difference between English and hindi da but anglophone adults cant)

• your eyes are conditioned to see sounds on lips what you hear vs what you see is different for adults vs babies

Developmental research designs

• you can combine both longitudinal and cross-sectional

longitudinal design

• researchers examine the characteristics of the same individual over their lifespan

• very expensive and time-consuming

• selective attrition: some people might quit or die meaning it doesn’t represent the original population and is biased since only enthusiastic participants are left

• practice effects: the participants may improve over time since the same test is being performed over many years

cross-sectional design

• people from many age groups are tested at once

• cohort effects: cannot tell apart age effects from generational effects (e.g. millennials have technology)

• not directly tracking developmental change with age only making inferences

Quasi-experiments

• group our subjects based on their existing attributes

• can’t manipulate key variables like age or sex

• e.g. two-year-olds placed in one group and five-year-olds into a separate group. subjects are not randomly assigned to different levels of age

• cannot make ‘cause and effect’ conclusions

• make correlation conclusions

Question Types

Normative

• how behaviors or processes change as one ages

• e.g. what are the behavioral and physiological changes throughout an individual’s normal development? and what specific behaviors are correlated to each age.

Analytic Questions

• the underlying mechanisms that drive changes in behaviors or processes as one ages

Development 2

Neural Development

• Neurogenesis is the process by which new neurons are formed in the brain

Prenatal

• nervous systems starts developing 21 days after conception forming the neural plate which turns into neural tube and eventually to brain and spine

• neural tube is lined with stem cells that create all nervous system cells

• human brain regions (forebrain, midbrain, hindbrain) are visible after 28 days

• the brain is distinctly human after 100 days

• after 210 days (7 months) sulci and gyri (raised and folded structures on the cerebral cortex of the brain) are formed

Infancy and Childhood

• rapid increase in synapses because learning patterns make new neural connection

• after the first year of life until 10 synaptic pruning decreases synapses in the brain

• synaptic pruning is an adaptive process that makes an overabundance of synapses and gets rid of necessary and incorrect ones so only the strongest and most useful stay

• experiences and genetic predisposition determined which synapses persist

Adolescence

• second wave of synapse production that gets pruned

• changes in the frontal lobe (self-control, judgment, emotions, and planning)

• aggravating teenage behaviors (poor decision-making, recklessness, emotional outbursts)

• can enhance brain development by engaging in activities like abstract thought, problem-solving, physical activity, music

Adulthood

• neurogenesis exists in learning and memory

• in cases of brain injury, stroke or diseases, neurogenesis is found in other brain areas

• experience-dependent plasticity helps adapt to change, injury, and decline in sensory input

• to promote plasticity you must give the brain relevant things to do

• e.g. exercise stimulates brain cell growth and connections, sharpens judgment, and improves memory

• fluid intelligence (abstract thinking and quick reasoning) declines with age

• crystallized intelligence (accumulated knowledge) remains stable and may even increase because of further experience

Brain development

• the development of the visual system is both experience-dependent and expectant

• e.g. ocular dominance columns: when one eye works better than the other because visual neurons respond to one eye better because one eye receives less input early in life so it depends on experience. it’s also expectant because our brain expects there to be the same strength of input for each eye

experience expectant brain growth

• the brain has evolved to expect a certain amount of environmental input to develop normally

• e.g. needs ordinary levels of social visual and auditory input

• sufficient stimulation

experience-dependent brain growth

• your brain develops according to personal experiences

• subtle changes in brain structures

• e.g. playing violin for years makes you develop calluses on your fingers

• beyond normal development

Twins

• monozygotic twins are genetically identical since they come from the same sperm and ovum

• dizygotic twins are separate zygotes so they are as similar as non-twin siblings

• the children of two monozygotic couples are cousins and genetic siblings

Genetic Transmission

• humans have 23 pairs of chromosomes, one from each parent

• the complete set of DNA of an organism is called genome

Genetic Expression

• genotype is an individual’s inherited genes

• phenotype is the expression of the genotype as an observable characteristic

• many factors can interact with a genotype to determine the observed phenotype such as environmental factors like nutrition

simple dominant receive inheritance

• expression of gene is determined by a single pair of alleles

polygenic inheritance

• most genes are polygenic rather than dominant-recessive

• the expression of a trait through the interaction of many traits like height and eye color

• the cascade gene model suggests that the sex gene is one of the many genes that determine sex

• e.g. androgen insensitivity syndrome is when someone is a male but resistant to male hormones. therefore they have female characteristics but male genitalia

codominance

• two dominant alleles are fully and equally expressed

• e.g. blood types: A and B are dominant and O is recessive

sex-linked inheritance

• recessive genes on the x chromosome are expressed in males since they have a Y

• females don’t usually express this since they have another X but they are carriers

• Y-linked disorders are rare and passed from father to son

Canalization principle

• the genotype restricts the phenotype to a closed number of possible developmental outcomes within a species

• e.g. all species will have the same phenotypic traits even if they have different environments

• therefore some developmental processes are protected from change by the environment

• e.g. all babies babble no matter where they’re from

Range of reaction principle

• the life experiences and environmental interactions produce a certain number of phenotypes and guides the expression of our genotype

combining both

• for your height, your species sets a limit on how tall or short you can be (canalization)

• where you fall within that range is determined by your environment and how it causes certain genes to be expressed (range of reaction)

• e.g. height range across optimal and poor environments is determined by genotype

Genes influence environment

passive genotype/environmental correlations

• parents raise their children in an environment that complements the parent’s genes

• e.g athletic parents create an athletic environment vs academic parents

evocative correlations

• inherited traits affect how others react and behave towards you

• e.g. a good kid receives positive responses from caregivers

active correlations

• genotype influences the environments you seek

• e.g. sensation seeking temperments seek thrilling environments

across lifespan

• when young, passive influence the most because you cannot choose your parents do

• as you grow older active increases since you can make your own decisions

• evocative stays the same throughout life

Headstart vs getting ahead

• hungry children going to school had interventions to help them get a breakfast and it improves academic performance, graduation rate, and adult health.

• extreme stimulation doesn’t predict extreme performance just because normal vs deprived stimulation differs

Biological Exuberance

• (excitement, curiosity, etc in babies) in babies is used to derive marketing for baby-enhancing products

Critical Periods

• a time in development when environmental stimulation is necessary to see permanent changes

• a kitten’s vision was deprived during a critical period and did not have normal visual input after. but this does not mean enhanced visual makes the visual input better after

• e.g. amblyopia or lazy eye happens if a cataract is not removed asap because ocular dominance columns were linked to nondeprived eye early in life

Sensitive Periods

• developmental periods where certain learning can happen easier but learning can also happen before or after

• less rigid than critical periods

• flexibility in timing and type of stimulation required for normal development

Plasticity

• if one sense doesn’t get enough stimulation the extra connections are used by other senses

• if someone was born blind, the brain modifies itself by maintaining extra connections between visual and somatosensory (touch) that would be pruned in a non-blind person. this is why blind people have a better sense of touch and the visual cortex is active when they read Braille

Mozart Effect

• the Mozart Effect tested music and spatial task performance. people who listen to classical music have higher IQ scores. However, only young adults were tested, only spatial reasoning improved and it only lasted a short amount of time.

Piaget

• Suggested specific stages of development, each with unique characteristics.

• reality is more fluid and children have a greater grasp of logic than Piaget originally proposed

• his theories were not perfect but he made a huge contribution to developmental research