Learn something new in 60 seconds
A few hundred of the 106,000 ideas in edgi, each explained on its own page with a Lesson you can play right there. Grouped into Sets, the way edgi collects them.
Cancer Is Evolution, Sped Up
A tumor isn't an invader. It's your own cells, mutating and competing by the exact rules that built every species on Earth.
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Mutation
A mutation is a permanent change in the chemical sequence of an organism's DNA.
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Natural Selection
Natural selection is the process where organisms with traits better suited to their environment survive and reproduce more successfully.
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Oncogene
An oncogene is a mutated or overactive gene that has the potential to cause cancer.
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Tumor suppressor gene
A tumor suppressor gene is a stretch of DNA that produces proteins to control cell division and stop abnormal cell growth.
Every Word Is a Fossil
'Salary' really does come from the Latin for salt. Nobody knows why. Every word you know is hiding a story like that.
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Etymology
Etymology is the scientific study of the origins of words and how their sounds and meanings change over time.
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Loanword
A loanword is a word that one language adopts directly from another without translating it into existing native roots.
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History of English
How Anglo-Saxon roots, Viking grammar, Norman French vocabulary, and the Great Vowel Shift formed modern English.
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Comparative method
Linguists use the comparative method to trace systematic sound changes across modern languages and reconstruct prehistoric ancestral tongues.
How ChatGPT Actually Works
ChatGPT predicts the next token. The surprising part is what training and feedback can build on top of that.
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ChatGPT
ChatGPT is an artificial intelligence chatbot that generates text, speech, and images in response to user prompts.
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Hallucination (artificial intelligence)
An AI hallucination is a false or misleading statement generated by an artificial intelligence model and presented as true fact.
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Embedding (machine learning)
An embedding is a list of numbers that represents complex data like words or images so a computer can work with them mathematically.
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Self-Supervised Learning
Self-supervised learning has a model make its own labels from raw data: it hides part of an input and learns by predicting it.
How Forensics Actually Works
A cousin's ancestry test caught the Golden State Killer. A confident eyewitness is the most common way to convict the wrong person.
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Fingerprint
A fingerprint is an impression left by the raised friction ridges on the skin of a human finger.
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Investigative genetic genealogy
How police use consumer DNA databases and distant relatives to build family trees that identify criminal suspects and unidentified victims.
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DNA profiling
DNA profiling is a laboratory technique that determines an individual's unique genetic characteristics.
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Locard's exchange principle
Locard's exchange principle is the rule that whenever two objects make physical contact, they transfer material between them.
How Immune Cells Decide What to Kill
Almost every cell in your body carries an ID badge. Show the wrong one, or none, and your own immune system kills it.
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Immunology
Immunology is the branch of biology and medicine that studies how immune systems protect organisms from disease.
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Killer T Cells
Killer T cells are white blood cells that hunt and destroy infected or cancerous cells by recognizing antigens displayed on MHC molecules.
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Major histocompatibility complex
Learn how the Major Histocompatibility Complex (MHC) presents protein fragments on cell surfaces to help T cells detect viruses and cancers.
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Natural killer cell
Natural killer cells are white blood cells that destroy tumor and virus-infected cells lacking normal MHC class I identity markers.
How Living Cells Became Medicine
Every drug you've ever taken eventually wears off. This one hunts, multiplies, and remembers.
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T cell
Learn what T cells are, how they develop in the thymus, and how killer and helper T cells coordinate specific immune defenses.
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Antigen
An antigen is any molecule that can latch onto a specific immune receptor or antibody, acting like a chemical identifier.
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Antibody
An antibody is a specialized protein produced by immune cells to identify and latch onto foreign invaders like viruses and bacteria.
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Single-chain variable fragment
A single-chain variable fragment is an engineered fusion protein that links the binding tips of an antibody into a compact sensor.
How Money Actually Grows
Nobody gets rich picking well. They get rich by starting early and not spending the difference.
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Compound Interest
Compound interest adds earned interest back to your starting principal, causing savings and debts to grow faster over time.
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Index Fund
An index fund mirrors a published market list instead of picking stocks, cutting fees and reliably outperforming most active managers over time.
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Inflation
Inflation is a general rise in the average price of goods and services across an entire economy.
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Dollar-cost averaging
Dollar-cost averaging invests a fixed sum on a set schedule, automatically buying more units when prices fall and fewer when they rise.
How Quantum Physics Actually Works
Fire electrons at two slits one at a time, and they still paint stripes that no single particle should.
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Schrödinger's Cat
Schrödinger's cat is a thought experiment showing the paradox of quantum superposition, where a cat in a sealed box is both alive and dead.
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Double-Slit Experiment
How the double-slit experiment proved wave-particle duality by showing light and matter act as waves until they are measured.
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Wave-Particle Duality
Wave-particle duality shows that fundamental objects like electrons and photons behave as waves or particles depending on how they are measured.
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Quantum Superposition
Quantum superposition is the principle where a physical system exists in multiple possible states simultaneously until it is measured.
The Six Chemicals Behind Every Mood
Your feelings have names, dosages, and half-lives. You never learned any of them.
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Dopamine
Dopamine is a chemical messenger that nerve cells use to communicate with one another.
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Adrenaline
Adrenaline is a hormone produced by the adrenal glands that prepares your body to react to danger or stress.
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Noradrenaline
Noradrenaline is a chemical messenger in your body and brain that acts as both a hormone and a neurotransmitter.
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Cortisol
Cortisol is a steroid hormone produced by your adrenal glands that mobilizes energy and helps regulate the immune system.
The Slot Machine in Your Pocket
Your phone runs on the same reward schedule as a casino floor.
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Infinite scrolling
Infinite scrolling dynamically loads content as you move down a page, replacing pagination and removing natural stopping points.
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Slot machine
A slot machine picks its result with a random number generator the instant you press spin.
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Operant Conditioning
Operant conditioning is a learning process where voluntary actions change based on the rewards or punishments that follow them.
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Dopamine
Dopamine is a chemical messenger that nerve cells use to communicate with one another.
Why Everything Takes Longer Than You Think
Your estimate was a hope, not a measurement.
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Planning fallacy
The planning fallacy causes people to underestimate the time, costs, and risks of their own future tasks while overestimating the benefits.
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Hofstadter's law
Hofstadter's law is the rule that complex work always takes longer than expected, even when you factor in the law itself.
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Parkinson's law
Parkinson's law states that work expands so as to fill the time available for its completion.
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Time Management
Time management is the practice of consciously planning and controlling how much time you spend on specific activities.
Your Body Never Sees Food
You ate a sandwich. Nothing that reached your blood had ever been a sandwich.
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Blood Sugar Levels
Blood sugar level is the concentration of glucose, a simple sugar used for energy, dissolved in your bloodstream.
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Essential amino acid
Humans cannot synthesize nine of the amino acids used to build proteins, meaning they must be supplied entirely by the foods in your diet.
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Intestinal villus
An intestinal villus is a tiny, finger-like projection lining the inside wall of the small intestine.
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Portal vein
The portal vein is a large blood vessel in the abdomen that carries blood from the digestive organs and spleen straight to the liver.
Alzheimer's Is Bad Origami
A protein is just a chain folded into a shape. Fold it wrong and it can take your mind, or spread like an infection with no DNA at all.
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Protein folding
Proteins fold from simple amino acid chains into functional 3D shapes within milliseconds, driven by sequence, water, and chemical bonds.
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Proteostasis
Proteostasis is the cell's system for balancing the creation, folding, and destruction of all its proteins.
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Autophagy
Autophagy is the cell's waste recycling system.
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Amyloid beta
Amyloid beta is a small protein fragment naturally produced and released by brain cells every day.
Do You Have Free Will?
Your brain decides before 'you' do. So who's driving?
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Determinism
Determinism is the philosophical view that every event is the inevitable result of preceding events and the laws of nature.
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Laplace's Demon
Laplace's Demon is a thought experiment about a hypothetical intellect that knows the exact position and motion of every particle in existence.
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Block Universe
The block universe theory treats time as a fourth dimension where past, present, and future events are all equally real and fixed.
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Fatalism
Fatalism is the view that fate fixes every event, so no choice can change it.
How Gothic Cathedrals Got Their Windows
Gothic isn't a spooky style. It's a 12th-century engineering campaign with one obsession: deleting the wall.
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Stained Glass
Stained glass is coloured glass cut into shapes and joined into panels, traditionally using grooved lead strips called cames.
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Romanesque architecture
Romanesque architecture is a medieval European building style defined by thick stone walls, sturdy pillars, and semicircular arches.
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Rib vault
A rib vault is an arched ceiling frame made of crossed stone ribs filled in with thin masonry panels.
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Flying buttress
A flying buttress is an outside stone arch that carries a vault's outward push to a separate pier, so Gothic walls could hold huge stained-glass windows.
How Habits Actually Form
You cannot delete a habit. You can only give the cue somewhere else to go.
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Habit
A habit is a routine behavior that is repeated regularly and occurs with little to no conscious thought.
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Stimulus control
Stimulus control occurs when a behavior happens in the presence of a specific cue and does not happen in its absence.
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Automaticity
Automaticity is the ability to carry out actions and mental tasks without thinking about the low-level steps.
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Basal ganglia
The basal ganglia are a group of interconnected structures deep beneath the cerebral cortex.
How Muscle Actually Grows
What actually tells a muscle to grow, and what only feels like it.
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Skeletal muscle
Skeletal muscle is the striped tissue attached to your bones that contracts to move your skeleton and keep your body upright.
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Muscle Hypertrophy
Muscle hypertrophy is the enlargement of skeletal muscle caused by individual muscle cells growing thicker rather than multiplying.
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Myosatellite cell
A myosatellite cell is a dormant stem cell nestled against the outer edge of a skeletal muscle fiber.
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Progressive overload
Progressive overload is the training principle of gradually increasing the stress placed on your muscles and nervous system.
How Scientists Test What Kills Cells
Before a cancer drug reaches a patient, it has already killed cells in a dish, and someone counted exactly how many.
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Chemotherapy
Chemotherapy is a systemic cancer treatment that uses drugs to disrupt cell division and trigger cell death.
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Cytotoxicity
Cytotoxicity is the ability of a substance to damage or kill living cells.
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Cell Culture
Cell culture is the process of growing living cells outside their natural organism inside controlled laboratory vessels.
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Assay
An assay is a laboratory test that detects or measures a specific target substance, called an analyte, in a sample.
The Con Artist's Toolkit
Every scam ever run pulls the same few levers. Learn them before someone uses them on you.
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Cold reading
Cold reading uses high-probability guesses and subtle body language cues to make strangers reveal their own details while believing the reader knew them.
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Social proof
Social proof occurs when people copy others to determine correct behavior during uncertain situations, often leading to genuine belief.
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Authority bias
Authority bias is the tendency to assume an opinion or order is accurate simply because it comes from an authority figure.
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Reciprocity (social psychology)
Reciprocity is the social norm of returning favors and harms in kind.
Why Money Is Worth Anything
Your money isn't backed by gold. It's backed by everyone agreeing not to ask what's underneath.
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Barter
Barter is a system of exchange where people trade goods or services directly for other goods or services without using money.
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Gold Standard
A gold standard is a monetary system where the basic unit of currency is defined as a fixed quantity of gold.
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Fiat Currency
Fiat currency is money issued by a government that is not backed by gold, silver, or any other physical asset.
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Central Bank
A central bank is a financial institution that manages the monetary policy of a country or monetary union.
Evolution Keeps Inventing the Same Thing
Unrelated animals keep discovering the exact same engineering solution, independently, from scratch.
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Bioluminescence
Bioluminescence is the production of light by a living organism through a chemical reaction.
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Convergent Evolution
Convergent evolution is the independent development of similar traits in species from completely different evolutionary branches.
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Animal echolocation
Animal echolocation uses sound emission and returning echoes to measure object distance, size, and velocity in air and water.
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Electroreception
Electroreception is the biological ability to detect electrical fields in the surrounding environment.
How Your Immune System Actually Works
Almost everything you call being sick is your own defense switching on.
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Fever
A fever is a temporary rise in body temperature caused by the brain resetting its internal thermostat to a higher target.
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Inflammation
Inflammation is your body's emergency biological defense against injuries, infections, and damaged tissue.
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Adaptive immune system
The adaptive immune system is the specialized part of your body's defenses that learns to recognize and destroy specific pathogens.
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Antibody
An antibody is a specialized protein produced by immune cells to identify and latch onto foreign invaders like viruses and bacteria.
Stoicism, From a Slave and an Emperor
The same philosophy worked from the bottom of Rome to the very top.
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Marcus Aurelius
Marcus Aurelius was a Roman emperor and Stoic philosopher who governed the Roman Empire from 161 to 180 AD.
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Zeno of Citium
Zeno of Citium was a Hellenistic philosopher from Cyprus who founded the Stoic school of philosophy around 300 BC.
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Epictetus
Epictetus was a Greek Stoic philosopher who taught that suffering comes from trying to control external events rather than our own actions.
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Gaius Musonius Rufus
Musonius Rufus was a 1st-century Roman Stoic who taught Epictetus, argued women need the same education as men, and was exiled by Nero.
Why Eating Less Makes You Live Longer
Eat less and something ancient flips inside your cells, from 'grow' to 'repair.' Two ordinary pills now flip it for you.
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Calorie restriction
Calorie restriction lowers energy intake while maintaining essential nutrients, shifting cellular resources toward repair and metabolic health.
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mTOR
mTOR, or mechanistic target of rapamycin, is an enzyme inside your cells that acts as a master growth switch.
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AMP-activated protein kinase
AMP-activated protein kinase (AMPK) is an enzyme inside cells that acts as a low-energy sensor.
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Sirtuin
Sirtuins are an ancient family of signaling proteins that act as master regulators of cellular metabolism and DNA repair.
Why GPS Needs Einstein
Your phone's blue dot only works because engineers correct for time itself bending. GPS is a daily test of Einstein.
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Global Positioning System
The Global Positioning System (GPS) is a network of satellites that broadcasts precise time and location radio signals down to Earth.
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Atomic Clock
Atomic clocks measure time using resonant atomic frequencies, defining the SI second as 9,192,631,770 oscillations of a caesium-133 atom.
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Speed of Light
The speed of light is the universal speed at which electromagnetic waves and massless particles travel through a vacuum, which is empty space.
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Special Theory of Relativity
The Special Theory of Relativity is a physics theory describing the relationship between space and time for objects moving at constant speeds.
Why You Love the Way You Do
Your dating patterns were set before you could talk.
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Attachment Styles
Attachment styles describe patterns infants use to stay close to caregivers, shaping expectations in future relationships.
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Strange situation
How Mary Ainsworth's 21-minute laboratory test uses separations and reunions to measure the attachment relationship between babies and caregivers.
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Harry Harlow
Harry Harlow was an American psychologist who studied maternal separation, dependency, and social isolation in rhesus monkeys.
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Imprinting (psychology)
Imprinting is a rapid learning process during a brief early window that permanently shapes an animal's social and mating preferences.
CRISPR and the Tools We Stole From Microbes
We can edit the code of life like text, and every tool for it was stolen from the microbes that invented it first.
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CRISPR
CRISPR is a microbial defense mechanism that stores virus DNA fragments and guides Cas enzymes to cut matching genetic sequences.
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DNA Sequencing
DNA sequencing determines the precise order of bases in genetic material, shrinking full-genome reads from thirteen years to under a day.
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Polymerase Chain Reaction
Polymerase Chain Reaction (PCR) is a laboratory method that rapidly makes billions of copies of a specific piece of DNA.
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Plasmid
A plasmid is a small loop of DNA that sits outside a cell's main chromosome and can copy itself independently.
Catchiness Is a Formula
The song you can't get out of your head didn't get there by luck. It was built to lodge there.
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Earworm
An earworm is a catchy piece of music or a phrase that continuously loops in your mind without your deliberate choice.
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Catchiness
Catchiness is a measure of how easily a tune, phrase, or advertising slogan is remembered and how hard it is to forget.
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Pop Music
Pop music is a commercial genre designed for broad public appeal rather than a specific subculture or ideology.
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Rhythm
Rhythm is the regular flow of movement or sound created by alternating strong, accented elements with weaker ones.
Every Bubble Runs the Same Script
Tulips, dot-coms, 1929. Every bubble swears it isn't one. It always is.
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Stock market crash
A stock market crash is a sudden, dramatic drop in share prices across a major part of the market, causing a massive loss of paper wealth.
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Tulip Mania
In 1630s Holland, prices for rare tulip bulbs soared to the cost of luxury homes before collapsing in history's first asset bubble.
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Economic bubble
An economic bubble happens when asset prices surge far past their real fundamental value, driven by easy liquidity and market psychology.
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Speculation
Speculation is trading assets purely to profit from short-term price swings rather than underlying business or commodity value.
How a Neuron Actually Fires
A thought is electricity, right up until the last millimeter.
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Axons
An axon is the long, slender cable that extends from a nerve cell to send electrical signals to other cells.
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Action Potential
An action potential is a fast electrical spike across a cell membrane that lets neurons, muscles, and endocrine cells send signals.
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Myelin Myelin is a fatty coating that wraps around nerve fibers to insulate them and speed up electrical signals.
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Synapse
A synapse is the microscopic junction where a nerve cell passes signals to another cell.
The Happiness Trap
Chasing happiness is the one reliable way to lose it.
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Hedonic treadmill
Learn what the hedonic treadmill is, how psychological adaptation restores our happiness set point, and why big life events rarely change our mood forever.
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Paradox of hedonism
The paradox of hedonism is the observation that deliberately chasing pleasure often prevents you from experiencing it.
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Hedonism
Hedonism is a family of philosophical ideas built on the claim that pleasure is the primary good and pain is the primary bad.
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Subjective well-being
Subjective well-being measures personal evaluations of life through emotional moods, life satisfaction, and meaning rather than external wealth.
How Your Hormones Actually Work
Hormones don't message one cell. They blast every cell in your body at once and wait.
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Insulin
Insulin is a hormone produced in the pancreas that signals cells to absorb glucose from the bloodstream.
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Hypothalamus
The hypothalamus is an almond-sized brain structure located below the thalamus that connects your nervous system to your hormone system.
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Pituitary Gland
The pituitary gland is a tiny hormone-secreting organ at the base of the brain that directs the rest of the endocrine system.
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Adrenal Glands
Learn how the adrenal cortex and medulla produce hormones like cortisol and adrenaline to manage metabolism, blood pressure, and stress.
The Cognitive Biases You Can't Turn Off
Your brain lies to you predictably, and always in the same direction.
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Confirmation Bias
Confirmation bias leads people to seek, interpret, and remember evidence that fits their prior beliefs while ignoring contrary facts.
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Dunning-Kruger Effect
The Dunning-Kruger effect is a cognitive bias where people with low ability in a specific area overestimate their competence.
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Hindsight bias
Hindsight bias makes past events seem predictable after they happen, distorting memories and creating false confidence about future forecasts.
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Self-serving bias
Why we attribute our successes to personal skill and blame our failures on outside factors to protect our self-esteem.
How Would We Know If AI Thinks?
Philosophers wrote the tests for thinking machines decades before the machines existed. Now the machines pass.
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Turing Test
Alan Turing replaced the question of machine thinking with a test: can a computer converse well enough through text to pass as human?
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Chinese Room
John Searle's thought experiment showing that a computer running a program can mimic human conversation without understanding it.
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Moravec's Paradox
Moravec's paradox, set out by Hans Moravec in 1988: computers handle chess and calculus with ease but struggle with what a toddler does without thinking, like walking or recognizing a face.
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Artificial General Intelligence (AGI)
Artificial general intelligence is hypothetical software that can learn, reason, and solve novel problems across any domain without reprogramming.
How the Algorithm Radicalizes People
Nobody sat in a smoky room deciding to radicalize your uncle. A recommendation algorithm did it one click at a time.
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Clickbait
Clickbait uses sensational headlines and hidden information to manipulate users into clicking links that overpromise and underdeliver.
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Attention Economy
When information becomes abundant, human attention becomes the scarce resource that platforms and advertisers compete to capture.
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Illusory truth effect
The illusory truth effect is the cognitive tendency to believe false information is true after hearing it repeated multiple times.
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Echo chamber (media)
An echo chamber is a closed media system where repeated beliefs amplify preexisting views and insulate people from opposing facts.
How the Stock Market Actually Works
Wall Street's geniuses, on average, lose to a fund that buys everything and sleeps.
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Stock Market
A stock market is a collection of buyers and sellers trading shares, which represent fractional ownership claims on companies.
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Hedge Funds
How hedge funds use leverage, short selling, and complex trading to make money whether financial markets rise or fall.
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Efficient Market Hypothesis
The Efficient Market Hypothesis is an economic theory stating that asset prices always reflect all available information.
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Expense ratio
An expense ratio is the percentage of your total invested money taken out each year to cover running a fund.
What Caffeine Is Actually Doing to You
From a shrub in Ethiopia to the drug 2 billion people take daily.
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Coffee
Coffee is a dark, bitter beverage brewed by steeping roasted and ground seeds from Coffea plant fruits in hot water.
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Coffea
Coffea is a genus of tropical flowering shrubs and trees in the madder family, Rubiaceae.
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Coffee Bean
A coffee bean is not a true bean, but the seed of a fruit called a coffee cherry grown on the Coffea plant.
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Caffeine
Caffeine is a central nervous system stimulant, a chemical that speeds up messaging between your brain and body.
What Sleep Is Actually For
You know you slept badly. You are the last to notice what it cost.
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Sleep debt
Sleep debt is the cumulative effect of not getting enough sleep over days or weeks.
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Chronotype
A chronotype is a person's natural biological tendency to sleep and be active at specific times during a 24-hour day.
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Circadian Rhythm
Circadian rhythms are roughly 24-hour internal biological cycles.
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REM Sleep
REM sleep is a distinct phase of sleep where the brain acts nearly awake while the body's skeletal muscles are paralyzed.
Your Gut Has Its Own Mind
Your gut has more neurons than your spinal cord, and it doesn't answer to your brain.
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Gut Microbiome
The gut microbiome contains 10 to 100 trillion microbes that ferment fiber, make vitamins, and influence mood via the gut-brain axis.
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Enteric nervous system
The enteric nervous system is a mesh of 500 million neurons lining your digestive tract that runs your digestion.
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Myenteric plexus
The myenteric plexus is a mesh-like network of nerve cells embedded between the muscle layers of your digestive tract.
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Vagus nerve
The vagus nerve is the longest cranial nerve in your body, running from your brainstem down into your chest and abdomen.
Confidence Is a Skill, Not a Trait
The confident aren't fearless or gifted. They learned the room isn't watching, and they ran the reps.
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Impostor syndrome
Impostor syndrome is the belief that your skills, accomplishments, and success are fraudulent, despite clear evidence that you are competent.
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Spotlight effect
The spotlight effect causes people to overestimate how much others notice their appearance, mistakes, and nervous feelings.
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Learned helplessness
Learned helplessness is giving up after stress you couldn't control.
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Locus of control
Locus of control is how much you think your own actions, rather than luck or other people, decide what happens to you.
Spicy Is Not a Taste
Your tongue has no receptor for heat. What you feel is your mouth reporting an injury that never happened.
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Chili Peppers
Chili peppers are the berry fruits of plants in the genus Capsicum, part of the nightshade family.
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Capsaicin
Birds can't feel capsaicin: their TRPV1 receptor doesn't react to it, so they eat chilies and spread the seeds.
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TRPV1 Receptors
TRPV1 receptors are ion channels in sensory nerve cells that detect scalding heat, acids, and pungent chemicals like capsaicin.
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Scoville Scale
The Scoville scale is a measurement system that rates the heat of chili peppers in units called Scoville Heat Units (SHU).
The Brain Under Construction
The brain you have right now is not the one you were issued. It's still being built.
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Critical period
A critical period is a developmental window where the nervous system requires specific environmental input to wire essential functions.
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Neurogenesis
Neurogenesis is the biological process where neural stem cells divide and create new neurons, the signaling cells of the nervous system.
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Hippocampus
The hippocampus is a curved structure tucked inside each side of the brain that turns new experiences into long-term memories.
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Synaptogenesis
Synaptogenesis is the process where neurons form synapses, which are the specialized communication junctions between nerve cells.
How America Rolls Over Its Debt
The national debt is not one giant bill. It is a schedule of IOUs, with old ones coming due while Treasury sells new ones.
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Deficit spending
Deficit spending is the amount by which spending exceeds revenue over a specific period, usually a single fiscal year.
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National debt of the United States
The cumulative money borrowed by the US government to cover budget deficits, tracked as outstanding Treasury securities.
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United States Treasury security
United States Treasury securities are debt instruments issued by the government and used as cash equivalents worldwide.
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Auction
An auction is a process of buying or selling goods and services through bids, which are offers of a specific price or terms.
How LSD Actually Works
It started as a fungus on rye bread. Then a chemist, the CIA, Congress and psychiatry each found out what it does to a brain.
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LSD
LSD is a powerful semisynthetic psychedelic drug derived from ergot, a fungus that grows on rye.
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Ergotism
Ergotism is toxic poisoning caused by eating fungus-infected rye or grain.
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5-HT2A receptor
The 5-HT2A receptor is the primary excitatory serotonin receptor in the brain and the main docking target for psychedelic drugs like LSD.
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Default Mode Network
The default mode network is a coordinated set of brain regions that fires up when you are not focused on the outside world.
Why the Sky Is Empty of Aliens
The math says the sky should be full of aliens. It isn't. Every explanation is worse.
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Fermi Paradox
The Fermi paradox exposes the clash between the high statistical odds of alien life across billions of stars and our complete lack of evidence for it.
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Copernican Principle
The Copernican principle states that Earth occupies an average position in space and that humans are not privileged observers of the universe.
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Drake Equation
The Drake equation is a mathematical formula that estimates how many active, communicative alien civilizations exist in our galaxy.
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Panspermia
Panspermia is the scientific hypothesis that microscopic life originated elsewhere and spreads across the universe inside rocks and comets.
Your Brain on Money
Why smart people make dumb financial decisions, on schedule.
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Loss Aversion
Loss aversion is a cognitive bias where losing something hurts more than gaining the exact same thing feels good.
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Prospect theory
Prospect theory is an economic theory describing how real people make decisions involving risk and uncertainty.
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Anchoring effect
The anchoring effect is a bias where people rely too heavily on an initial reference number when estimating values or making financial decisions.
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Mental accounting
Mental accounting explains how people separate identical money into subjective buckets, changing how they spend and evaluate financial decisions.
How Fermentation Actually Works
Your favorite foods are controlled spoilage.
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Sourdough
Sourdough is bread leavened by wild yeast and lactic acid bacteria living in a fermented flour starter.
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Fermentation
Fermentation is a chemical process where cells break down sugars to make energy without using oxygen.
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Yeast
Yeast is a single-celled fungus that survives and reproduces by consuming sugars for energy.
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Kimchi
Kimchi is a traditional Korean side dish made of salted and fermented vegetables, most commonly Napa cabbage or Korean radish.
Why You Procrastinate
Procrastination is not laziness. It is emotion regulation gone wrong.
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Procrastination
Procrastination is needless delay to dodge a task's bad feelings; the relief keeps it going.
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Perfectionism (psychology)
Perfectionism is a personality trait defined by striving for flawlessness, critical self-evaluations, and tying self-worth to productivity.
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Fear of negative evaluation
Fear of negative evaluation is the dread of being judged badly.
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Avoidant coping
Avoidant coping reduces stress by evading a problem rather than fixing it, bringing immediate relief at the cost of compounding future damage.
How Debt Actually Works
A credit card charges 22% and a mortgage charges 6% for the same reason, and it is not your credit score.
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Interest
Interest is an extra fee a borrower pays to a lender on top of returning the original amount borrowed.
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Credit card debt
Credit card debt is money owed to a card issuer after buying goods or services and not paying the balance immediately.
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Payday loan
A payday loan is a small, short-term unsecured loan designed to be repaid in full when the borrower receives their next paycheck.
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Usury
Usury is the practice of lending money at interest rates that are unfairly high or exceed legal limits.
How Ultra-Processed Food Hooks You
Engineered to be impossible to stop eating.
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Instant noodle
Instant noodles are precooked, dried blocks of noodles that rehydrate in boiling water in just a few minutes.
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Ultra-processed food
Ultra-processed foods are industrial formulations made with additives and modified ingredients that bypass standard digestion and satiety.
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Hyperpalatable food
Hyperpalatable foods combine specific ratios of fat, sugar, salt, and carbs to overstimulate brain reward circuits and bypass fullness cues.
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Food processing
Food processing is the transformation of raw agricultural products into edible food, or of one form of food into another.
How to Not Forget What You Learn
Almost all of what you forget, you forget on the first day.
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Forgetting curve
The forgetting curve shows that memory loss is steepest right after learning.
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Testing effect
The testing effect is the memory boost from recalling information instead of rereading it.
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Spaced repetition
Spaced repetition is a learning method where you review information at increasing intervals of time instead of all at once.
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Levels-of-processing effect
The levels-of-processing effect is the finding that how well you remember something depends on how deeply you analyze it during encoding.
How Wine Tasting Actually Works
Sommeliers aren't tasting magic you can't. They're naming a handful of variables, and every one is learnable.
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Aroma of wine
Wine flavor is mostly smell sensed by the olfactory bulb, originating from odorless grape compounds unlocked by fermentation and aging.
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Sweetness of wine
How residual sugar, acids, and alcohol determine wine sweetness, from legal dry limits to dessert styles like Tokaji and Sauternes.
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Acids in wine
Wine contains organic acids like tartaric and malic that shape its taste, protect it from bacteria, and can form harmless crystals on the cork.
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Tannins
Tannins are large, astringent biomolecules produced by plants that bind to proteins and force them out of solution.
What Stress Actually Does to Your Body
Stress is not in your head. It is a body-wide budget with compounding interest.
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Burnout (psychology)
Occupational burnout stems from unmanaged workplace stress.
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Psychological stress
Psychological stress is a reaction to perceived demands.
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Stress Hormone
A stress hormone is a chemical signal released by endocrine glands to adjust your body during times of threat.
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Allostatic load
Allostatic load is the cumulative physical wear and tear on your body caused by chronic or repeated stress.
It's All Just Salt
Pink, flaky, kosher, sea. The expensive ones are marketing.
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Salt
Salt is a crystalline mineral made mostly of sodium chloride, a compound of sodium and chlorine.
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Sodium Chloride
Sodium chloride is an ionic compound made of equal parts sodium and chlorine ions, commonly known as table salt or the mineral halite.
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Kosher salt
Kosher salt is a coarse, additive-free salt named after meat preparation, valued by chefs for controlled seasoning, lower density, and clean flavor.
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Sea salt
Sea salt is salt produced directly by evaporating seawater, either through open-air solar pans or fueled heat.
The Experiments That Proved You'd Obey
The classic experiments that proved it: you would have complied too.
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Asch Conformity Experiment
Solomon Asch tested group conformity using line lengths, finding that a single dissenting voice can drop conformity by 80 percent.
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Conformity
Conformity is the act of changing your beliefs, attitudes, or behaviors to match the norms of a group.
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Social Norms
A social norm is a shared standard of acceptable behavior within a group.
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Groupthink
Groupthink is a psychological pattern where members of a tight-knit group prioritize getting along over critically testing ideas.
The Science of the Swipe
Attraction is more mechanical than you would like it to be.
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Tinder (app)
Tinder is a geosocial dating and networking app where people browse nearby profiles by swiping right to like or left to pass.
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Online dating
Online dating uses digital profiles to connect romantic partners, revealing stark patterns in how age, race, and education affect attraction.
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Facial Symmetry
Facial symmetry is the structural balance between the left and right sides of a person's face.
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Averageness
Averageness is the physical beauty that occurs when blending human facial features into a mathematical mean.
How Therapy Actually Works
The mechanisms under the couch. What actually changes in your head.
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Cognitive Behavioral Therapy (CBT)
Cognitive behavioral therapy treats automatic negative thoughts as unverified hypotheses, combining cognitive reframing with new behavioral habits.
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Cognitive Distortions
A cognitive distortion is an exaggerated or irrational thought pattern that causes you to perceive reality inaccurately.
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Cognitive reframing
Cognitive reframing is a technique where you identify and change the way you view situations, thoughts, or emotions.
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Exposure therapy
Exposure therapy treats anxiety by confronting fear triggers without escaping, helping the brain learn that the feared outcome will not occur.
The Freud Files
How Freud explained dreams, desire, childhood and the talking cure.
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Sigmund Freud
Sigmund Freud founded psychoanalysis, explaining how unconscious desires, dreams, and slips of the tongue shape human behavior.
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Id, ego and superego
The id, ego, and superego are three interacting parts of the mind that Sigmund Freud proposed to explain internal conflict.
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Freudian Unconscious
The Freudian unconscious is the part of the mind holding hidden thoughts, drives, and memories that a person cannot inspect directly.
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Oedipus complex
Sigmund Freud defined the Oedipus complex as childhood desire for one parent and rivalry with the other, shaping adult conscience and neurosis.
The Flow State
Attention is the scarcest resource you own. This is its physics.
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Attention Span
Attention span is the amount of time someone concentrates on a task before becoming distracted.
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Flow (psychology)
Flow is a mental state where you become completely absorbed in an activity, losing track of time and outside distractions.
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Mihaly Csikszentmihalyi
Hungarian-American psychologist Mihaly Csikszentmihalyi identified flow, the state of deep absorption where challenge matches high skill.
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Distraction
Distraction is the process of pulling attention away from a chosen focus, which blocks or reduces the intake of relevant information.
The Narcissist's Script
The pattern is a script. Once you know its beats, you cannot unsee it.
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Gaslighting
Gaslighting is the psychological manipulation of a person into questioning their own perception of reality.
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Narcissism
Narcissism is a self-centered personality style marked by an excessive preoccupation with oneself and one's own needs, often at the expense of others.
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Narcissistic personality disorder
Narcissistic personality disorder is a psychiatric condition defined by grandiosity, low empathy, and impaired relationships across 256 trait combinations.
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Love Bombing
Love bombing is the act of overwhelming someone with intense affection, flattery, and attention to influence them.
Why a Song Takes You Back
Three notes of a song you have not heard in years, and you are seventeen again.
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Encoding specificity principle
Information is easiest to retrieve when the physical, auditory, or mental state at recall matches the conditions present during learning.
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Amygdala
The amygdala is a pair of almond-sized clusters of neurons located deep inside the temporal lobes of the brain.
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Frisson
Frisson is a brief physical reaction to rewarding stimuli like music or art that creates skin tingling, goosebumps, and pleasure.
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Reminiscence bump
The reminiscence bump is why adults over forty remember more from ages 10 to 30 than from any other time of life.
How Friendship Actually Works
A close friend takes about 200 hours together. Where you happen to spend your days decides who gets them.
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Friendship
Friendship is a relationship of mutual affection between people that is stronger than an acquaintance or casual association.
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Proximity principle
The proximity principle explains why people form relationships with those physically nearby due to familiarity and repeated passive contact.
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Self-disclosure
Self-disclosure is the communication process where one person shares private information about themselves with another person.
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Interpersonal ties
Interpersonal ties are the information-carrying connections between individual people in a social network.