25 Best Topics to Learn on Your Own (With Free Quizzes to Test Yourself)
Why Self-Directed Learning Works (When Done Right)
The failure mode of self-directed learning is passive consumption: reading articles, watching YouTube videos, listening to podcasts, and feeling informed without actually retaining anything or being able to apply it.
The antidote is testing. After studying any topic, testing yourself on the concepts reveals immediately whether you understood it or just recognized it. Recognition and recall are different cognitive processes — recognition is easy, recall is what actually matters.
Each topic below includes a link to a free quiz on Prismer that tests real understanding, not just surface familiarity.
Thinking and Decision-Making
1. Critical Thinking
Why learn it: The ability to evaluate arguments, spot logical fallacies, and assess evidence is useful in every domain — from reading news to making decisions to writing persuasively. Most people significantly overestimate how well they think critically.
Where to start: Start with informal logic and cognitive biases. The Stanford Encyclopedia of Philosophy has excellent free resources. Thinking, Fast and Slow by Daniel Kahneman covers the psychological dimensions.
Test yourself: Critical Thinking Quiz
2. Logic and Reasoning
Why learn it: Formal logic underlies mathematics, computer science, philosophy, and rigorous argumentation. Understanding deductive and inductive reasoning makes you harder to fool and clearer in your own thinking.
Where to start: Khan Academy has a free logic course covering propositional logic. Bertrand Russell's Introduction to Mathematical Philosophy is accessible for beginners.
Test yourself: Logic & Reasoning Quiz
3. Behavioral Economics
Why learn it: Classical economics assumes people are rational. Behavioral economics explains why they're not — and why that matters for everything from personal finance to product design to policy. Understanding cognitive biases helps you recognize them in yourself.
Where to start: Predictably Irrational by Dan Ariely is the most accessible entry point. Kahneman's Thinking, Fast and Slow goes deeper.
Test yourself: Behavioral Economics Quiz
4. Game Theory
Why learn it: Game theory models strategic interactions — situations where your best move depends on what others do. It applies to negotiation, competition, cooperation, voting, and everyday decisions you might not recognize as strategic.
Where to start: Yale's free Game Theory course on Coursera (by Ben Polak) is one of the best free resources available. Start with the prisoner's dilemma and Nash equilibrium.
Test yourself: Game Theory Basics Quiz
5. Probability and Statistics
Why learn it: Poor probabilistic thinking is behind most bad decisions under uncertainty. Understanding base rates, conditional probability, and statistical significance changes how you interpret news, medical studies, and risk.
Where to start: Khan Academy's statistics course is comprehensive and free. The Drunkard's Walk by Leonard Mlodinow covers the intuition behind probability without heavy mathematics.
Test yourself: Probability & Statistics Basics Quiz
Science and the Physical World
6. Evolution
Why learn it: Evolutionary theory is the organizing framework for all of biology, medicine, and behavioral science. Understanding natural selection, genetic drift, and speciation changes how you understand human behavior, disease, and life itself.
Where to start: Richard Dawkins' The Selfish Gene is the clearest introduction to thinking in evolutionary terms. Jerry Coyne's Why Evolution Is True covers the evidence comprehensively.
Test yourself: Evolution 101 Quiz
7. Intro to Quantum Mechanics
Why learn it: Quantum mechanics is counterintuitive enough that most people's mental model of it is wrong. Understanding the basics — superposition, wave-particle duality, entanglement — corrects misconceptions and reveals how genuinely strange physical reality is.
Where to start: Richard Feynman's QED: The Strange Theory of Light and Matter is the most accessible introduction written by someone who actually understood it. Sean Carroll's Something Deeply Hidden goes deeper.
Test yourself: Intro to Quantum Mechanics Quiz
8. Intro to Relativity
Why learn it: Special and general relativity changed our understanding of space, time, and gravity. Understanding time dilation, length contraction, and the equivalence of mass and energy (E=mc²) gives you a more accurate model of physical reality.
Where to start: Einstein's own popular explanation Relativity: The Special and the General Theory is surprisingly accessible. Brian Greene's The Elegant Universe provides modern context.
Test yourself: Intro to Relativity Quiz
9. The Science of Sleep
Why learn it: Sleep affects cognition, memory consolidation, emotional regulation, and physical health more than almost any other factor — yet most people dramatically underestimate its importance and consistently underinvest in it.
Where to start: Matthew Walker's Why We Sleep is the definitive popular science treatment. It covers REM sleep, circadian rhythms, the consequences of sleep deprivation, and what actually helps.
Test yourself: The Science of Sleep Quiz
10. Nutrition Fundamentals
Why learn it: Nutrition is one of the most confusing areas for non-experts because of contradictory headlines and industry-funded research. Understanding macronutrients, micronutrients, and evidence-based nutritional principles helps you make better decisions and evaluate health claims.
Where to start: How Not to Die by Michael Greger covers the evidence-based fundamentals. The Examine.com database is excellent for looking up specific claims with citations.
Test yourself: Nutrition Fundamentals Quiz
11. Exercise Science
Why learn it: Most people exercise without understanding the physiology behind it — which means they often train inefficiently or in ways that don't match their goals. Understanding progressive overload, energy systems, and recovery changes how you approach physical training.
Where to start: The New Rules of Lifting series covers evidence-based training principles. Andy Galpin's podcast goes deep on exercise physiology for serious learners.
Test yourself: Exercise Science 101 Quiz
Technology and the Digital World
12. Intro to AI
Why learn it: AI is reshaping every industry. Understanding how machine learning actually works — not at a coding level but at a conceptual level — helps you evaluate AI claims, understand its limitations, and use AI tools more effectively.
Where to start: Fast.ai's free practical course is excellent. 3Blue1Brown's neural network video series on YouTube is the clearest visual explanation of how neural networks work.
Test yourself: Intro to AI Quiz
13. Cryptography Basics
Why learn it: Cryptography underlies every secure digital interaction — HTTPS, end-to-end encryption, digital signatures, and cryptocurrency. Understanding the basics helps you make better decisions about digital privacy and security.
Where to start: The Code Book by Simon Singh covers the history and fundamentals accessibly. Khan Academy has a good free cryptography course.
Test yourself: Cryptography Basics Quiz
14. Blockchain Explained
Why learn it: Blockchain technology is frequently hyped and poorly understood. Learning how distributed ledgers, consensus mechanisms, and smart contracts actually work helps you evaluate claims about cryptocurrency and Web3 more accurately.
Where to start: The Bitcoin whitepaper (9 pages) is surprisingly readable. Ethereum's documentation explains smart contracts clearly.
Test yourself: Blockchain Explained Quiz
Philosophy and the Big Questions
15. Intro to Philosophy
Why learn it: Philosophy covers the questions that underlie everything else: how do we know what we know, what makes something morally right, what is consciousness, what is a good life? Engaging with these questions seriously changes how you think.
Where to start: Simon Blackburn's Think is the best accessible introduction. The Stanford Encyclopedia of Philosophy is the best free reference for going deeper on any topic.
Test yourself: Intro to Philosophy Quiz
16. Existentialism
Why learn it: Existentialism — Sartre, Camus, Kierkegaard, Nietzsche, de Beauvoir — addresses questions about meaning, freedom, and authenticity that most people grapple with whether or not they've named them. Understanding the tradition gives you a framework for thinking through these questions rigorously.
Where to start: Camus' The Myth of Sisyphus is the most accessible entry. Sartre's Existentialism is a Humanism is a short lecture that covers the basics of his position.
Test yourself: Existentialism Explained Quiz
Economics and Money
17. Economics 101
Why learn it: Supply and demand, market failures, incentives, GDP, inflation — economic concepts appear everywhere in news, policy, and everyday decisions. A basic understanding of microeconomics and macroeconomics makes you a more informed citizen and better decision-maker.
Where to start: The Worldly Philosophers by Robert Heilbroner covers the history of economic thought accessibly. MRU (Marginal Revolution University) has excellent free video courses.
Test yourself: Economics 101 Quiz
18. Personal Finance
Why learn it: Compound interest, tax-advantaged accounts, index funds, insurance, and budgeting — understanding personal finance fundamentals has a larger practical impact on most people's lives than almost any other knowledge.
Where to start: The Simple Path to Wealth by JL Collins covers index fund investing clearly. Ramit Sethi's I Will Teach You to Be Rich covers the practical mechanics of personal finance setup.
Test yourself: Personal Finance 101 Quiz
Psychology and the Mind
19. Psychology 101
Why learn it: Understanding cognitive biases, classical and operant conditioning, memory, perception, and social influence helps you understand yourself and others more accurately. Psychology also gives you a vocabulary for things you've already noticed but couldn't name.
Where to start: Robert Cialdini's Influence covers the psychology of persuasion. Thinking, Fast and Slow covers cognitive biases and dual-process theory.
Test yourself: Psychology 101 Quiz
20. Managing Your Emotions
Why learn it: Emotional regulation — the ability to understand and manage your emotional responses — is consistently linked to better relationships, decision-making, and mental health. It's a learnable skill, not a fixed trait.
Where to start: Emotional Intelligence by Daniel Goleman introduced the concept. How Emotions Are Made by Lisa Feldman Barrett is the more scientifically rigorous modern take.
Test yourself: Managing Your Emotions Quiz
21. Intro to Mindfulness
Why learn it: Mindfulness — the practice of present-moment non-judgmental awareness — has substantial evidence for reducing anxiety, improving focus, and increasing wellbeing when practiced regularly. Understanding the concepts helps you practice more effectively.
Where to start: Jon Kabat-Zinn's Full Catastrophe Living covers the evidence and practice. The Waking Up app (Sam Harris) provides structured audio courses.
Test yourself: Intro to Mindfulness Quiz
Skills and Creative Domains
22. Music Theory
Why learn it: Music theory is the grammar of music — understanding why chord progressions create tension and release, why certain melodies feel inevitable, and how rhythm and harmony interact makes you a better musician and a more perceptive listener.
Where to start: musictheory.net is the best free structured introduction. The Complete Musician by Steven Laitz is the standard college textbook.
Test yourself: Music Theory Basics Quiz
23. Color Theory
Why learn it: Understanding how colors interact — complementary relationships, warm and cool temperatures, contrast and harmony — is essential for design, photography, art, and visual communication of any kind.
Where to start: Josef Albers' Interaction of Color is the foundational text. Canva's free design school covers practical applications.
Test yourself: Color Theory Quiz
24. Photography Composition
Why learn it: Composition — how to arrange elements within a frame — is the most learnable aspect of photography and has the largest impact on whether photos communicate effectively. Understanding rule of thirds, leading lines, depth of field, and framing transforms how you see and shoot.
Where to start: Bryan Peterson's Understanding Exposure covers the technical fundamentals. Scott Kelby's photography books cover composition practically.
Test yourself: Photography Composition Quiz
25. How to Learn Effectively
Why learn it: Meta-learning — understanding how learning itself works — is the highest-leverage knowledge available. Understanding spaced repetition, active recall, the testing effect, and interleaving means every hour you spend learning produces more than it would otherwise.
Where to start: Make It Stick by Brown, Roediger, and McDaniel is the most accessible summary of the learning science research. Barbara Oakley's A Mind for Numbers covers practical applications.
Test yourself: How to Learn Effectively Quiz
How to Use This List
Don't try to learn everything at once. Pick one topic that genuinely interests you, spend two to four weeks on it using good sources, and test yourself with the quiz to see how much you actually understood.
Then pick the next one.
The compounding effect of broad, deep self-education over years is one of the highest-return investments you can make. Each topic makes the others easier to understand — logic helps with game theory, psychology helps with behavioral economics, statistics helps with evaluating everything.
Want to test your understanding of any of these topics right now? All quizzes above are free, take 10-15 minutes, and test conceptual understanding rather than surface recall.