Complete Developmental Psychology Midterm I

Developmental Psychology

A method of studying human behavior that spans many discipline within psychology

Human development

The multidisciplinary study of how people systematically change over time

Hierarchical/self-organizing change

Each change is dependent on the preceding series of changes

Sea turtles vs. humans

Sea turtles never meet their parents; instead, they follow the moon after hatching. Humans, by contrast, depend on parental presence from birth for survival. Parenting is metabolically costly, burning about 50,000 extra calories a month to raise a single child.

Why are humans designed to need their parents for years when it is so expensive to raise one?

Evolutionarily, humans developed a long period of childhood because it comes with a payoff. Unlike apes, who become adults at 10, we have extra developmental stages. The benefit of a longer juvenile phase is that it gives humans extra brain plasticity.

Brain plasticity

Changes in neural pathways and synapses due to changes in behavior, environment, neural processes, thinking, and emotions, as well as changes resulting from bodily injury.

What does a longer time spent with a parent lead to?

A more sophisticated adult outcome

What does stimulating the brain do?

Can lead to changes that result in more cells and more sophisticated connections

Monkey Taped Finger Experiment

In monkeys, the somatosensory cortex has five regions for the five fingers. In an experiment, two fingers were tied together for months. After 5 months, the brain areas controlling the fingers merged, since separate control was no longer needed. In monkeys, the somatosensory cortex has five regions for the five fingers. In an experiment, two fingers were tied together for months. After 5 months, the brain areas controlling the fingers merged, since separate control was no longer needed.

Adult Juggling Experiment

A study taught adults with no juggling experience how to juggle. After three months of practice, they became skilled, and brain scans revealed that the region responsible for hand-eye coordination had almost tripled in size.

Theory

A set of concepts and propositions designed to organize, describe, and explain observation

Why do we need theories?

They give us explanatory structures for lots of the facts we get from experiments that we do; constrain interpretations of our research findings; help us predict future behavior; and help us understand the mechanisms of how things work

John Locke (1600s)

Saw children as tabula rasa (blank slates); our environment shapes who we are as individuals

Social Reform Movement

Established a legacy of research conducted for the benefit of children and provided some of the earliest descriptions of the adverse effects that harsh environments can have on child development (I.e., kids working in factories brought on reform for children's welfare)

What did Darwin’s theory of evolution do?

Inspired research in child development in order to gain insights into the nature of the human species.

Darwin (1800s)

The level of detail of human behavior across ontogeny parallels change at a species level or phylogeny. In ontogeny, there is a lot of variation in behaviors.

Ex) In babies, it shows they are constantly trying different ways to perform a specific task. Eventually, they will select the most efficient way.

Ontogeny

Change across a person’s lifetime

Phylogeny

Evolutionary change of a species over time

Variation (Darwin)

Refers to differences in thought and behavior within and among individuals

Selection (Darwin)

Describes the more frequent survival and reproduction of organisms that are well adapted to their environment

Sigmund Freud (1900s)

Founder of the psychoanalytic method, he believed people act on intrinsic and unconscious motives and drives, and that personality can only be understood by examining early childhood experiences.

Psychoanalytic/Psychodynamic Method

We have multiple parts of our personality that are at war with each other constantly. The Id, Ego, and Superego

Id (Freud)

It lives in our deep unconscious, driven by instincts and the desire to feel good. It is present at birth and already well developed

Ego (Freud)

Develops in early childhood and lives in both the conscious and unconscious. Grounded in reality, it gives us a sense of “I,” thinks rationally, and balances the demands of Id and Superego

Superego (Freud)

Mostly unconscious, it acts as our moral compass and is shaped by the standards we absorb from our environment.

Why is Freud important?

He showed that we are often driven by motives and mental processes we are unaware of, and that early experiences shape our personalities.

John Watson

One of the earliest leaders of behaviorism, he rejected Freud’s introspection and argued we are born as a blank slate. He believed our personalities, skills, and IQ develop through learning, and that conclusions about humans should be based only on observable behavior.

Classical (Pavlovian) conditioning

A learning process where something neutral is paired with something meaningful until it triggers an emotional or behavioral response.

Little Albert Experiment

Albert had no fear of rats at first, but every time he saw a rat, a metal bar was loudly struck behind his head. This conditioned him to fear the rat.

Unconditioned Stimulus

Something that reliably produces a naturally occurring reaction in an organism (ex. A loud noise startling a baby)

Unconditioned Response

A reflexive reaction that is reliably produced by an unconditioned stimulus (Ex. baby crying after hearing a loud noise)

Conditioned stimulus

A previously neutral stimulus that produces a reliable response (Ex. A rat paired with a loud noise)

Conditioned response

A learned reaction to a conditioned stimulus that resembles the unconditioned response. (Ex. Crying when seeing the rat, even without the noise.)

Operant Conditioning

A way of learning about behavior through consequences, where a natural behavior increases if reinforced and decreases if punished. Ex) giving a baby what it wants to stop crying reinforces crying.

_{3 Dimensions of developmental theory}

Nature vs Nurture, Activity vs Passivity, and Continuity vs Discontinuity

Nature vs Nurture

Nature = traits from DNA and genes from our parents. Nurture = the wide range of our physical environment and experiences that shape us. Development comes from both together. Ex) intelligence is shaped by genes and schooling

Activity vs Passivity

Passivity = development means being passively shaped by genes and environment. Activity = development means individuals influence their own growth through choices and actions. Ex) Picking classes or clubs actively shapes development. Letting external factors such as social norms and cultural influences have a greater impact on an individual's behavior passively shapes development.

Continuity vs Discontinuity 

Continuity is gradual, cumulative growth. Ex) steady increases in height. Discontinuity involves large, stage-like shifts where development looks qualitatively different. Ex) puberty is a discontinuous change.

Ecological Systems Approach (Bronfenbrenner)

Development occurs within concentric circles of environment. The microsystem is close settings (family, school, friends). The mesosystem is interactions among microsystems. Our exosystem are environments that indirectly affect us like parent’s job or media. The macrosystem is cultural and societal systems taht influence else. The chronosystem descirbes how all the levels change over time.

Key concepts in dynamic system theory

There are multiple influences, self-organizing, and have nonlinear change

Multiple Influences (DST)

Development is shaped by many systems all acting at once—biological (muscles, brain maturation), psychological (motivation, attention), environmental (parent support, physical surroundings), plus evolutionary history.

Self-Organizing (DST)

No single factor “causes” development. Instead, behavior emerges from the interaction of all the parts working together. Ex) a flock of birds creates a spontaneous pattern that emerges from collective movement

Rat Study on Genes and Environment

Two “bright-ish” and two “dull-ish” rats were bred. In a typical environment, the bright rats made about five errors while the dull rats made many more, showing genetic differences. But when raised in enriched or deprived environments, those differences disappeared. This shows that traits are not fixed by genes or environment alone. Instead, development is shaped by the interaction of rearing environment, evolutionary history, and the activity of the body and brain. These are developmental consequences, not simple genetic or environmental effects.

Nonlinear Change (DST)

Development doesn’t always follow a straight line. Progress can be sudden, with leaps forward, regressions, or plateaus.

Scientific Method

A way to test beliefs while reducing bias. Involves forming a research question, developing a hypothesis, and testing it. Used to study developmental change.

Ways to Approach Developmental Questions

Normative Development: Focusing on how a group changes (i.e., how most people are alike). Ex) At what age do most children begin walking?

Individual difference: Looking at individual variations in development (i.e., how people differ from each other). Ex) Why does one child start to walk earlier than another?

Longitudinal Design

Studies the same group over time to see age-related changes. Ex) Following 6-year-olds until age 10. Limitations include: attrition, funding loss, changing methods, and long study durations.

Cross-Sectional Design

Studies different age groups at the same time to infer age-related differences. Ex) Studying 6- and 10-year-olds at once. Challenge: does not directly measure change.

Cohort Effects

A disadvantage of both longitudinal and cross-sectional designs. Differences may reflect generational effects, not development. Ex) texting styles of 40-year-olds vs 20-year-olds show generational habits, not age-related change.

Sequential Design

Combines longitudinal and cross-sectional approaches by studying multiple cohorts over time. Allows researchers to compare different generations at the same ages and detect cohort effects.

Experimental Design

Uses random assignment so everyone has an equal chance of being in either condition. This removes external bias and allows researchers to infer causation. Ex) studying if listening to music while studying lowers test scores.

Correlational design

Measures how strongly two variables are associated. The correlation coefficient r ranges from -1 to 1. The closer to -1 or 1, the stronger the relationship. Correlation does not equal causation; a third variable may explain it. Ex) smoking and depression.

Developmental Methods

Ways to study development include observation, parent/teacher report, self-report surveys, and biological measures.

Habituation

A decrease in response to a repeated stimulus, showing learning and memory. Ex) babies lose interest in the sound “Ba”

Dishabituation

Renewed response to a new stimulus after habituation has occurred, showing the infant can tell the difference. Ex) baby re-engages when “Ba” changes to “Pa.”

Visual Paired Comparison Test

Infants prefer novelty. After habituation to one object, they are shown both the old and a new object. If they look more at the new one, it shows memory of the old.

Mobile Conjugate Reinforcement Study

Designed to test infant memory. An infant lies in a crib with a ribbon tied from their ankle to a mobile. By chance, the baby kicks, the mobile moves, and the baby learns the connection. Weeks later, the infant is tested again. Results: 2-month-olds remembered for about 3 days, 3-month-olds for over a week, and older infants remembered even longer. Shows memory duration increases with age.

Eyetracking in Developmental Research

Measures infant attention by tracking pupil and corneal reflection with infrared light. Shows infants are more sensitive to motion than angular deviations. Advantages: no response needed, works across ages and species. Disadvantages: hard with wiggly infants, motion-sensitive, needs individual calibration

Developmental Cognitive-Affective Neuroscience

Studies human behavior and brain development at a different phenotype level. Earlier relied on non-human models or children with illness, but now uses less invasive tools.

Structural Methods

Show what the brain looks like, not its activity. Ex) MRI for brain images, Diffusion Tensor Imaging (DTI) for connections between brain regions.

Functional Methods

Show brain activity. EEG records electrical signals at the scalp and generates ERPs. fMRI highlights brain areas active during a stimulus. fNIRS (“baby fMRI”) uses small sensors to track brain activity in infants.

EEG (Electroencephalography)

Measures brain activity from voltage at the scalp, producing wave-like readouts that reflect thought processes. A portion of the EEG tied to a stimulus is called an ERP. Advantages: excellent temporal resolution (milliseconds), real-time measurement, relatively cheap. Disadvantages: poor spatial resolution, sensitive to movement.

ERP (Event-Related Potential)

A segment of EEG that shows the brain’s response to a specific stimulus. Ex) babies who know the word “dog” show different ERP responses to matching vs non-matching sounds.

fMRI (Functional Magnetic Resonance Imaging)

Non-invasive measure of brain activity using blood flow changes. High spatial resolution but poor temporal resolution (seconds off). Disadvantages: very expensive, sensitive to movement (>0.5 mm movement can ruin data).

Limitations of fMRI

Uses subtractive methodology (Task A – Task B). Results can mislead if the control is poorly chosen. Ex) children vs adults and fearful vs neutral faces: children responded strongly to both, so subtraction falsely suggested weaker responses.

Rene Descartes

Asked how the mind and body are connected. Concluded the link was the pineal gland. Introduced dualistic thinking: the mind and body are separate.

Cerebral Cortex

The outer layer of the brain, split into two hemispheres with four lobes: occipital, parietal, temporal, and frontal.

Occipital Lobe

Located at the back of the brain. Responsible for vision and processing visual information.

Parietal Lobe

In front of the occipital lobe. Governs spatial processing and integrates sensory input with memory. Represents a visual stimulus in space even when you are not looking directly at it.

Temporal Lobe

On the sides of the brain. Control memory, visual recognition, processing of emotion, and auditory information.

Frontal Lobe

At the front of the brain. Includes the primary motor cortex and prefrontal cortex. The prefrontal cortex regulates attention, impulses, emotions, and thoughts.

Subcortical Cortex

Located under the lobes. Includes structures such as the amygdala, which is central to processing emotions.

Cortex in Evolution and Development

The mammalian brain has a cortex that controls behavior. It developed last both evolutionarily and in individual development.

C-Shaped Brain Development

Brain regions deep and in the back develop first. Growth then curls forward, with the frontal lobe developing last.

Neuron

The basic unit of the brain. Signals begin in dendrites and cell body, convert to electrical signals down the axon (covered by myelin), and cross the synapse via neurotransmitters.

Myelin Sheath and Saltatory Conduction

Myelin insulates the axon, speeding signals. Electrical impulses jump from node to node at the Nodes of Ranvier, a process called saltatory conduction.

Stages of Neural Development 

Neurons first proliferate (overproduced at birth), then migrate along chemical paths, aggregate with similar cells, differentiate into specialized types, form synapses (synaptogenesis), undergo apoptosis (cell death and synapse pruning), and finally myelinate for faster signaling.

Synaptogenesis

Formation of synapses through growth of axons and dendrites. Key to childhood development and human plasticity. Overproduction followed by pruning lets the brain adapt to any environment.

Peter Huttenlocher (1931–2013)

Neuroscientist who studied post-mortem human brains across ages to count synapses. His research revealed that all brain regions show synaptic overproduction followed by elimination (pruning) over time. Compared the occipital lobe (vision) with the prefrontal cortex (impulse control). Both showed this pattern but at different times.

Why does the brain go through the energy-intensive process of making and eliminating synapses?

It supports plasticity, the brain’s ability to adapt to any environment. Humans are born not knowing what world they will enter, so overproducing and pruning synapses allows flexible learning and adjustment. This Darwinian process ensures that only the most useful connections shaped by experience survive.

What determines which synapses survive?

Synapses that are activated by experience and environment remain, while unused ones are eliminated. Ex) infants start with synapses for all language sounds but lose those not reinforced by their native language.

Is synapse development uniform across the brain?

No, different brain regions develop at different times in a C-shaped pattern. Areas for vision mature early, while the prefrontal cortex, which controls impulse regulation and decision-making, develops last and continues pruning through adolescence into early adulthood.

What would human behavior be like without synaptic overproduction and pruning?

Without these processes, humans would lack diversity and adaptability. Everyone would develop the same away regardless of experiences. Plasticity allows us to mold to our environment, but efficiency increases as plasticity decreases over time.

Prefrontal Cortex Development

Develops slowly and continues pruning into adulthood. It supports impulse control, emotional regulation, and decision-making.

Phineas Gage (1848)

A railroad worker whose tamping iron accident severed connection between his prefrontal cortex and the rest of his brain. Afterward, he lost emotional control and social restrain, showing how the prefrontal cortex regulates behavior. Young children show similar immaturity because their prefrontal cortex is still developing.

Delay of Gratification Task (Marshmallow Test)

In this task, a child sits in front of a marshmallow and is told they will get more if they wait to eat it until the adult returns. Preschoolers usually do poorly, but performance improves around age 6. Children vary individually in how well they can delay gratification.

Go/No-Go Task and fMRI

Children see letters appear on a screen and must press a button for every letter except the letter “X.” Controlling the impulse to press the button is difficult for young children, who show more false alarms than older individuals. fMRI scans show developmental differences in the prefrontal cortex during this task.

Genetic Influences on Development

Genetic (Nature) refers to DNA. Humans have 46 chromosomes in each cell, except in ova and sperm, which have 23. Within chromosomes are nucleotides (G, T, A, C) that make up genes. Different versions of a gene are called alleles.

Genotype vs. Phenotype

Genotype is the genetic makeup (the sequence of G, C, T, and A). Phenotype is what is expressed. Traits like behavior, personality, height, and eye color. Genotype does not equal phenotype, since the environment also influences expression.

Central Dogma of Genetics

DNA is transcribed into mRNA and then translated into proteins, which affect brain function and behavior. This process is triggered by the chemical environment, which can be influenced by social or nutritional factors.

Rosalind Franklin, Watson, and Crick

Rosalind Franklin captured the X-ray image that allowed Watson and Crick to confirm the double-helix structure of DNA.

Phenylketonuria (PKU)

A genetic condition where individuals cannot metabolize phenylalanine, leading to intellectual disability if untreated. Changing the environment (diet) can prevent symptoms, showing that genes and environment interact.

Gene-Environment Interaction Example

Someone may have a gene for depression but never develop it if raised in a supportive environment. Environmental context influences gene expression.

Parent–Child Genetic and Environmental Influence

A parent’s genotype affects both the child’s genes and the child’s environment. The child’s behavior (phenotype) also influences how the parent responds, creating a feedback loop in development.

Reaction Range Principle

Imagine two people with different genotypes. The reaction range principle says that even in the same environment, the person with genotype A will never reach the height of the person with genotype B. If the person with genotype A is raised in the most favorable environment and the person with genotype B in the least favorable one, genotype A may end up taller. A factor influencing this could be access to nutrition.

Serotonin Gene and Depression

There are three genes involved with serotonin: s/s, s/l, and l/l. People with s/s have a high risk for depression if they experience early maltreatment, but if they do not, their risk is the same as someone with l/l. Those with l/l have a lower risk for depression regardless of maltreatment. People with s/l fall in between. This is why you also have to look at the environment and genetics together

Epigenetic Modification of DNA

Our gene activity can be influenced by the environment, which changes the structure of DNA, not the sequence. When a gene is tightly coiled, it is silenced because it cannot be transcribed. In a mouse study, controlling the maternal diet with folic acid led to identical twins having different phenotypes.

Twin Studies

Compare identical (monozygotic) and fraternal (dizygotic) twins to estimate heritability. If MZ twins share a trait more than DZ twins, it is seen as more genetically influenced. MZ twins also tend to share environments and evoke similar treatment from others.

Adoption Studies

Compare adopted children to biological and adoptive parents. If a child resembles biological parents more, the trait is genetically influenced. If the child resembles adoptive parents more, it is environmentally influenced.

Molecular Genetics

Identifies associations between specific genes and traits through studies like gene-wide association studies (GWAS) or candidate gene research. If a gene consistently appears with a trait, it is inferred that the gene influences that trait.