# The Behavioral Scientist > Explore applied behavioral science with lessons, evidence-based book reviews, in-depth guides, and practical tools from The Behavioral Scientist. ## Start here - [Behavior Change: The Complete Science-Based Guide](https://www.thebehavioralscientist.com/guides/behavior-change): What does the science actually say about behavior change? The real evidence on habits, nudges, personality, and what works, including what most guides leave out. - [The Death Of Behavioral Economics](https://www.thebehavioralscientist.com/articles/the-death-of-behavioral-economics): Jason Hreha challenges behavioral economics on replication and weak field results, arguing that effective behavior change needs creative solutions fitted to specific situations. - [Behavior Market Fit](https://www.thebehavioralscientist.com/articles/behavior-market-fit): Product Market Fit is actually the result of something much more important and fundamental: Behavior Market Fit. Behavior Market Fit is the match of the desired behavior (or behaviors) and customers. - [Behavior Change Models Compared: 16 Frameworks, Their Evidence and Practical Uses](https://www.thebehavioralscientist.com/articles/behavior-change-models-compared): Compare 16 behavior change models and frameworks by the questions they answer. Use a worked team handoff to connect behavior selection, investigation, design and evaluation. - [How Long Does It Take to Form a Habit? What Lally et al. (2010) Actually Found](https://www.thebehavioralscientist.com/articles/how-long-to-form-a-habit): The 66-day figure is a modeled median from a selected group in Lally’s study. Examine the full sample, exercise estimates and the difference between automaticity and effortless practice. ## Guides - [Guides for deeper understanding](https://www.thebehavioralscientist.com/guides): Jason’s guides to behavior change, behavioral design, behavioral economics and personality tests, plus reference material and a book summary. - [AI Adoption at Work: Choose the Task Before the Tool](https://www.thebehavioralscientist.com/guides/ai-adoption-at-work): Plan AI adoption at work by task: rate each task for fit, separate fear of AI from poor fit, and run a pilot that measures finished work and quality. - [Atomic Habits Cheat Sheet](https://www.thebehavioralscientist.com/guides/atomic-habits-cheat-sheet): A thorough breakdown of the classic habit building book by James Clear. Learn the fundamental laws and advanced tactics of creating new habits. - [Behavioral Economics Books: A Critical Reading Guide](https://www.thebehavioralscientist.com/guides/behavioral-economics-books): Compare 13 behavioral economics and related books. See what each helps explain, the evidence behind its claims, and its practical limits. - [Behavioral Economics Examples: What Actually Changed?](https://www.thebehavioralscientist.com/guides/behavioral-economics-examples): Examine studies of retirement saving, vaccination, exercise and government nudge programs. Learn what changed, how large the effects were and what the results mean in practice. - [Research Methods in Psychology and Behavioral Science: Choosing the Right Design](https://www.thebehavioralscientist.com/guides/behavioral-science-research-methods): Choose research methods for the question you need to answer. Compare observation, surveys, interviews, experiments and longitudinal designs, then write a concrete research-design brief. - [Change Management Models Compared: What the Evidence Supports](https://www.thebehavioralscientist.com/guides/change-management-models): Compare six change management models, from Lewin and Kotter to ADKAR and McKinsey 7-S: what each one claims, what the evidence supports, and how to choose. - [How to Choose a Personality Test](https://www.thebehavioralscientist.com/guides/choose-personality-test): Which personality test should you take? Compare 14 online tests: what each measures, which results are free, what the scores mean, and what happens to your answers. - [Employee Incentives: Designing for Quality, Quantity, and Cooperation](https://www.thebehavioralscientist.com/guides/employee-incentives): Before you launch an employee incentive program or bonus, check what it rewards, who controls the measure, and what work it might push aside. With a worksheet. - [How to Evaluate Personality Tests](https://www.thebehavioralscientist.com/guides/evaluate-personality-tests): Are personality tests accurate? Learn how to judge a test’s validity and reliability for your purpose and decide whether its results can help answer your question. - [How This Site Evaluates Tests](https://www.thebehavioralscientist.com/guides/how-this-site-evaluates-tests): The evidence standard behind this site’s test explanations: identify the instrument and use, distinguish research from provider claims, explain scores, and disclose commercial interests. - [Human-in-the-Loop AI: When Human Review Actually Helps](https://www.thebehavioralscientist.com/guides/human-in-the-loop-ai): Human-in-the-loop AI only helps if review improves decisions. Compare human, AI and combined results, count errors caught and created, and price the review. - [Personality Test Exercises for the Classroom](https://www.thebehavioralscientist.com/guides/personality-test-classroom-exercises): Teach students how to read personality test results with an invented report, percentile exercises, discussion questions, and an answer key. - [How to Read Personality Test Results](https://www.thebehavioralscientist.com/guides/read-personality-test-results): Learn to read personality test results with an example report covering raw scores, percentiles, comparison groups, labels, and practical decisions. - [How to Run a Sludge Audit of a Public Service](https://www.thebehavioralscientist.com/guides/sludge-audit): Run a sludge audit of a public service. Map the applicant's journey, measure administrative burden, separate safeguards from sludge, and test one fix. - [Structured Interviews: Questions, Scorecards, and Limits](https://www.thebehavioralscientist.com/guides/structured-interviews): Build a structured interview from a job analysis: example questions, an anchored scorecard, independent scoring, and what an interview cannot tell you. ## Evidence Library - [Evidence Library](https://www.thebehavioralscientist.com/learn/evidence): Which behavioral science findings hold up? 14 evidence reviews compare original studies with replications, later research and retractions on learning, decisions, personality and behavior change. - [Explicit and incidental anchoring: what replication studies found](https://www.thebehavioralscientist.com/learn/evidence/anchoring): Compare evidence for explicit numerical anchors, incidental consumer-price anchors and anchoring on willingness to pay, with limits on practical application. - [Ego depletion: does using self-control weaken it?](https://www.thebehavioralscientist.com/learn/evidence/ego-depletion): Large ego-depletion studies disagree across tasks. See what null replications and newer positive results mean for claims about a limited willpower resource. - [Facial feedback: does smiling make you feel happier?](https://www.thebehavioralscientist.com/learn/evidence/facial-feedback): The pen-in-mouth experiment failed a major replication. Other methods show small, immediate effects of posed smiles on mood; a 2026 Registered Report found the lift weakened when smiling was repeated or required. - [Do growth mindset interventions improve academic achievement?](https://www.thebehavioralscientist.com/learn/evidence/growth-mindset): Growth mindset interventions rarely deliver large academic gains. Examine targeted benefits, conflicting reviews, and what schools can reasonably expect. - [Do implementation intentions work? Evidence on if–then plans](https://www.thebehavioralscientist.com/learn/evidence/implementation-intentions): What if–then planning studies show, what vaccination and gym-attendance studies found, and how to assess a planning intervention. - [Does matching teaching to learning styles improve learning?](https://www.thebehavioralscientist.com/learn/evidence/learning-styles): An evidence review of learning-style matching: one small positive meta-analysis, a near-zero pooled estimate from four earlier matching meta-analyses, crossover tests that find no benefit, and the difference between preference and better learning. - [The marshmallow test: what does waiting really predict?](https://www.thebehavioralscientist.com/learn/evidence/marshmallow-test): What does the marshmallow test predict? Compare the original studies, later replications and two adult follow-ups without confusing prediction with causation. - [How well do nudges work at scale?](https://www.thebehavioralscientist.com/learn/evidence/nudges-at-scale): Nudge trials by two US government units raised the targeted behavior 1.4 percentage points on average, versus 8.7 in academic journals. Why DellaVigna and Linos trace most of the gap to selective publication, and when a small effect is worth it. - [Personality and life outcomes: what a major replication found](https://www.thebehavioralscientist.com/learn/evidence/personality-life-outcomes): What a large personality replication project found, why effects often shrank, how the links hold up in other samples, and what associations can tell you about individuals. - [Does power posing work? What the evidence supports](https://www.thebehavioralscientist.com/learn/evidence/power-posing): Power posing has not reliably changed hormones or risk-taking. See what replications and newer studies show about feelings and everyday performance, and why slumping matters more than posing. - [The 2002 procrastination and deadlines study: retraction and replication](https://www.thebehavioralscientist.com/learn/evidence/procrastination-deadlines): What the 2026 retraction, the close replication and Data Colada's analysis change about the 2002 procrastination and deadlines paper. - [Does retrieval practice improve learning?](https://www.thebehavioralscientist.com/learn/evidence/retrieval-practice): What classroom studies show about retrieval practice, where the benefits vary, and why better recall does not guarantee transfer to every task. - [Does signing at the top of a form reduce dishonesty?](https://www.thebehavioralscientist.com/learn/evidence/signing-first): The signing-first honesty claim, later replication findings, the official retraction of the original 2012 paper, and how honesty oaths differ from moving a signature. - [Does spaced practice improve learning?](https://www.thebehavioralscientist.com/learn/evidence/spacing-effect): The evidence for spaced practice, including recent replications, classroom and mathematics findings, a large school trial, and limits on claims about optimal schedules and learning apps. ## Subject hubs - [Behavioral economics: a field guide](https://www.thebehavioralscientist.com/behavioral-economics-glossary): Learn the main ideas in behavioral economics, from choice under uncertainty to social preferences and nudges. Follow learning paths or browse 271 terms. - [Cognitive biases](https://www.thebehavioralscientist.com/glossary/cognitive-biases): Explore more than 200 cognitive biases, heuristics, fallacies, and related concepts. Browse the A–Z list, follow a learning path, or start with a decision. - [Personality and individual differences](https://www.thebehavioralscientist.com/glossary/personality-and-individual-differences): Understand personality traits, models and individual differences. Find the Big Five, HEXACO, cognitive ability, historical theories and common personality labels. - [Personality tests and assessments](https://www.thebehavioralscientist.com/glossary/personality-assessments-and-tests): Find personality tests and assessments by purpose. Explore trait questionnaires, workplace profiles, interests, symptom measures, MBTI types and score interpretation. - [Research methods and evidence](https://www.thebehavioralscientist.com/glossary/research-methods-and-statistics): Learn how to read behavioral research. Explore causation, measurement, validity, statistics, bias, and replication, or browse 46 glossary terms. ## Glossary - [The behavioral science glossary](https://www.thebehavioralscientist.com/glossary): Definitions and explanations across psychology and applied behavioral science. ## Book reviews - [Behavioral science and psychology book reviews](https://www.thebehavioralscientist.com/book-reviews): Evidence-based reviews of behavioral science and psychology books, with ratings for scientific accuracy, reference accuracy, and practical value. - [Disclosures, notices & corrections](https://www.thebehavioralscientist.com/book-reviews/disclosures): Editorial review notices, AI and interest disclosures, and corrections policy for The Behavioral Scientist book review series. - [Emotional Intelligence review](https://www.thebehavioralscientist.com/book-reviews/emotional-intelligence): Daniel Goleman makes a persuasive case for taking emotional skills seriously. His larger explanation of success, development and health is less dependable. - [Good Habits, Bad Habits review](https://www.thebehavioralscientist.com/book-reviews/good-habits-bad-habits): Wendy Wood offers useful ways to make recurring actions easier. Her explanation of lasting change asks more of the evidence. - [Grit review](https://www.thebehavioralscientist.com/book-reviews/grit): Angela Duckworth is stronger on effective practice than on grit as a general explanation of success. - [Hooked review](https://www.thebehavioralscientist.com/book-reviews/hooked): Nir Eyal’s four-stage loop can focus a product team’s attention. That is different from proving how habits form. - [How to Change review](https://www.thebehavioralscientist.com/book-reviews/how-to-change): Katy Milkman offers practical ways to change behavior. Several of the stories used to explain them need correction. - [Influence, New and Expanded review](https://www.thebehavioralscientist.com/book-reviews/influence): Robert Cialdini collects useful findings about persuasion. His explanations of why they work—and his advice on protecting yourself—need a closer look. - [The Let Them Theory review](https://www.thebehavioralscientist.com/book-reviews/let-them-theory): Mel Robbins’s acceptance-and-action idea is most useful in ordinary life. Its scientific and clinical extensions need much more care. - [How we review books](https://www.thebehavioralscientist.com/book-reviews/methodology): Three category percentages, one overall rating, and the evidence behind both. - [Originals review](https://www.thebehavioralscientist.com/book-reviews/originals): Adam Grant expands the possibilities for creative work. The evidence is less dependable when possibilities become prescriptions. - [The Psychology of Money review](https://www.thebehavioralscientist.com/book-reviews/psychology-of-money): Morgan Housel offers useful advice about saving, patience, and preparing for setbacks. His claims about what matters most in wealth and happiness are less reliable. - [Range review](https://www.thebehavioralscientist.com/book-reviews/range): David Epstein makes a strong case for exploration, better learning, and combining expertise. His broader career advice needs more care. ## Tools - [Tools for behavior change.](https://www.thebehavioralscientist.com/tools): Build a behavior menu, clarify your values, check what a percentage difference means in practice, and explore the Real Change worksheets. Personality assessments are optional. - [Build a behavior menu](https://www.thebehavioralscientist.com/tools/behavior-menu): Compare possible actions and make your own small trial plan. No test or account required. - [Practical-Effect Calculator](https://www.thebehavioralscientist.com/tools/practical-effect-calculator): Compare two percentages, translate their difference into a count for your group, and estimate what each added or avoided result would cost.