Developmental Psychology

Cognitive development

Mental capacities that help a person think and reason, including memory, retention, and knowledge about facts.

Sensorimotor stage

Piaget's first stage of development, occurring from age $0-2$ years, where children use physical senses and motor skills to explore the world.

Preoperational stage

Piaget's second stage ($2-6$ years) where children use symbols and language to represent objects but still do not reason logically.

Concrete operational stage

Piaget's third stage ($7-12$ years) where children begin to think logically about concrete objects following rules like conservation.

Formal operational stage

Piaget's final stage starting at $12+$ years where thought becomes increasingly flexible and abstract.

Discontinuous development

Piaget's theory that children stay in one stage for a period before making a sudden, qualitatively different leap to the next stage.

Primary circular reactions

The first sensorimotor substage ($1-4$ months) where children repeat pleasurable actions centered on their own body.

Secondary circular reactions

The second sensorimotor substage ($4-8$ months) where children repeat actions using their bodies and other objects to trigger a response.

Tertiary circular reactions

The sensorimotor substage ($12-18$ months) where children engage in trial and error experimentation with the environment.

Object permanence

The cognitive milestone where a child understands that an object continues to exist even when it is out of sight.

Preconceptual stage

The first substage of preoperational thought ($2-4$ years) characterized by egocentric speech and symbolic play.

Intuitive stage

The second substage of preoperational thought ($4-7$ years) where speech becomes more social and children show curiosity about others' perspectives.

3 mountains task

A task used by Piaget to investigate perspective-taking, showing that young preoperational children are often egocentric.

Conservation task

A test of concrete operational thought proving the understanding that quantity remains constant despite changes in container shape.

Information Processing Theories

Theories focusing on the underlying quantitative processes of thinking, such as encoding, memory, and attention, similar to a computer.

Vygotsky's Sociocultural Theory

A theory emphasizing that cognitive development is shaped by social interactions and cultural context rather than independent exploration.

Zone of Proximal Development (ZPD)

The gap between what a child can do unassisted and what they can achieve with the guidance of a more competent person.

Scaffolding

A process where a more experienced person provides a temporary framework to support a child's learning at a level just beyond their current ability.

Functional play

Play typical of the first $2$ years involving simple, repetitive movements and learning about cause and effect.

Constructive play

Play occurring from age $3-15$ involving the physical manipulation of objects to build or create something.

Games with rules

Formal play governed by fixed conventions, typical of children aged $6-15$ in the concrete operational stage.

Theory of Mind (ToM)

The ability to understand and comprehend that someone else's perspective, thoughts, or knowledge may differ from one's own.

Core Knowledge Theories

Theories proposing that infants are born with innate, domain-specific knowledge in areas of evolutionary importance like objects, number, and agents.

Violation of expectation

An experimental paradigm where infants' surprise at 'impossible' events is used to infer their innate knowledge or expectations.

Cephalocaudal trend

The general principle that motor development proceeds from the head downward to the arms, torso, and legs.

Rooting reflex

An innate reflex where an infant turns their head with an open mouth when touched on the cheek, assisting in feeding.

Visual acuity

The clarity of vision, which is poor at birth ($14\text{ cm}$ distance) but develops to adult-like levels by $8-12$ months.

Joint attention

The social act of focusing on the same object or event with another person, often involving eye gaze alternation.

Shared intentionality

The ability to participate with others in collaborative activities with shared goals, intentions, and enjoyment.

Private speech

Self-directed speech used by children for self-guidance and problem-solving, which eventually is internalized as thought.

Behaviorist view of language

The theory by Skinner that language is learned through imitation and positive reinforcement without innate mechanisms.

Linguistic/Nativist view

Chomsky's theory that children possess an innate Universal Grammar and a language acquisition device to solve the poverty of stimulus.

Statistical learning

The domain-general ability to track patterns and distributional regularities in the environment to learn phonemes or word boundaries.

Broca's area

A region in the left inferior frontal gyrus essential for speech production.

Wernicke's area

A brain region in the left superior temporal gyrus involved in processing word meanings and linguistic input.

Critical period

A specific time window (e.g., up to age $5$ or $17$) during which an individual must be exposed to language to achieve native-like proficiency.

Phonemes

The shortest segments of speech that distinguish one word from another in a specific language.

Categorical perception

The phenomenon where the brain imposes discrete categories on a continuous physical stimulus, such as voice onset time ($\text{VOT}$).

Transitional probabilities (TPs)

The likelihood of one syllable following another, used by infants to identify word boundaries in continuous speech.

Fast mapping

The ability of children to learn the meaning of a word after only one or two exposures to the label.

Indeterminacy of reference

Quine's problem (Gavagai) that a word's meaning is logically under-constrained and could refer to many different things.

Shape bias

The tendency of children, emerging in the second year, to categorize novel objects based on their form rather than color or texture.

Mutual exclusivity

A word-learning heuristic where children assume that each object has only one label.

Morphemes

The smallest units of language that convey meaning, such as prefixes, suffixes, and root words.

U-shaped curve

The developmental pattern in verb morphology where children start with correct usage, then overgeneralize rules (e.g., 'goed'), and finally return to correctness.

Genotype

The specific genetic information a person inherits that has the potential to influence observable properties of an organism.

Phenotype

The observable properties of an organism produced by the genotype and environmental influences.

Down's Syndrome (Trisomy 21)

A condition caused by non-disjunction results in 3 chromosomes on the 21st chromosome pair, totaling 47 chromosomes.

Mutations

Changes in the structure or amount of DNA caused by mutagenic agents like chemicals or radiation.

Meiosis

A reduction division process that produces four daughter sex cells (gametes), each with 23 chromosomes.

Karyotype

An image of a person's chromosomes isolated from an individual cell and arranged in numerical order and size.

Autosomes

The 22 pairs of non-sex chromosomes numbered 1-22.

Klinefelter Syndrome ($XXY$)

A condition occurring in males involving an extra X chromosome, resulting in 47 chromosomes and potential fertility or language issues.

Turner Syndrome ($XO$)

A chromosomal disorder in biological females characterized by a missing X chromosome ($45, X$).

Sister Chromatids

Two chromatids joined at the centromere to form a distinct X-shape after DNA replication.

Nucleotides

Subunits of DNA consisting of a phosphate group, a pentose sugar (deoxyribose), and a nitrogenous base.

Complementary Base Pairing

The specific alignment of nitrogenous bases where Adenine pairs with Thymine ($A \leftrightarrow T$) and Guanine pairs with Cytosine ($G \leftrightarrow C$).

Locus

A sequence of DNA situated on a specific region of a chromosome, representing the location of a gene.

Transcription

The process in the nucleus where a DNA strand acts as a template for the synthesis of messenger ribonucleic acid ($mRNA$).

Translation

The process in the cytoplasm where the code written as mRNA is converted into a chain of amino acids at the ribosome.

Codons

Groups of three bases of mRNA that specify a particular amino acid during protein synthesis.

Alleles

One or two or more forms or variations of a gene that influence the same trait or characteristic.

Tay-Sachs Disease (TSD)

A fatal, autosomal recessive neurodegenerative disease caused by mutations of the $HEXA$ gene on chromosome $15q23-q24$.

Huntington's Disease (HD)

An autosomal dominant neurodegenerative disorder caused by over 40 repeats of the $CAG$ trinucleotide on chromosome 4.

Fragile-X Syndrome (FXS)

The most common inherited intellectual disability, caused by a $CGG$ repeat expansion in the $FMR1$ gene on the X chromosome.

Polygenic Inheritance

When traits or disorders (like height or schizophrenia) are governed by the combination of many genes working together.

CRISPR-Cas9

A gene editing tool that uses a component to pinpoint a DNA sequence and an enzyme to snip through it for alteration or replacement.

Norm (Range) of Reaction

All the phenotypes that could theoretically result from a given genotype across all possible environments.

Orchid Children

Children who are highly sensitive to their environment, showing great susceptibility to both positive and negative situations.

Epigenome

A record of chemical changes to DNA and histone proteins that can turn genes on or off without changing the DNA sequence.

DNA Methylation

An epigenetic mechanism that silences gene expression by blocking transcription in the promoter region.

Standardized Residuals

Values in a Chi-Square test that identify which specific cells contribute most to an association; values greater than $\pm 2$ suggest significance.

Phylogenetic Continuity

The idea that humans share certain genetic characteristics and developmental processes with animals due to a shared evolutionary history.

Zygote

A fertilized egg with a full complement of 46 chromosomes (23 from each parent).

Teratogens

External environmental agents, such as medicine, drugs, or radiation, that can cause damage or death during prenatal development.

Marasmus

A nutritional disease affecting babies who receive insufficient protein and too few calories, leading to tissue wasting.

Kwashiorkor

A nutritional disease affecting children who receive enough calories but have a severe protein deficiency, often after being weaned.

Enteric Nervous System (ENS)

Known as the 'second brain,' it consists of 400-600 million neurons in the gastrointestinal tract and can function autonomously.

Glial Cells

Cells that provide structural support, produce myelin, and serve as the brain's immune system (microglia).

Myelination

The process where oligodendrocytes form an insulating fatty sheath around axons to increase signal speed and efficiency.

Neurogenesis

The process of generating new neurons from neural stem cells, which begins 42 days after conception.

Arborisation

The increase in the size and complexity of a neuron's dendritic tree, allowing for more connections.

Synaptic Pruning

A 'use it or lose it' process where the brain eliminates approximately 40% of unused synapses to maintain efficiency.

Experience-Dependent Plasticity

The process by which neural connections are constantly created and reorganized based on specific individual experiences.