Experiments
Playable versions of canonical experiments
Sit one yourself in a few minutes, or run it with a class and compare the room’s results against the published figures. Instructors can attach any of these to a course from the class dashboard.
The experiments marked “runs on nat-hansen.com” are hosted there, and that site never receives your name, email, or account; the rest run here.
Socratic questionnaires
A dynamic thought experiment: you give a verdict, then an interlocutor draws out the principle behind it and hands you the case that tests it. Where an ordinary questionnaire records the first answer and stops, these follow your answer several steps and record any changes to your view. The method is set out in Hansen, Francis & Greening, “Socratic Questionnaires,” Oxford Studies in Experimental Philosophy 5 (2024).
The Trolley ProblemA Thought Experiment, in Dialogue
A runaway trolley, five people on the track, and a lever in your hand. You say what you'd do; the tutor asks why; then the footbridge case arrives and turns your own principle against you. A short Socratic walk through the most-taught thought experiment in moral philosophy — built so a whole classroom's verdicts can be gathered and compared.
Academician tier, or a class code from your instructor
Gettier CasesA Thought Experiment, in Dialogue
Is knowledge just justified true belief? This tutorial presents a case where all three conditions are met but many people do not think is a case of knowledge. It then draws out your diagnosis of what went wrong before giving you another case that challenges analyses of knowledge in a different way. A short Socratic questionnaire introduction to the analysis of knowledge, prompted by Edmund Gettier's 1963 paper.
Academician tier, or a class code from your instructor
The Side-Effect EffectA Thought Experiment, in Dialogue
A chairman signs off on a program that will boost profits — and, as a side effect, change the environment. He says he doesn't care about the environment either way. Did he bring that side effect about *intentionally*? You give your answer, then the tutor draws out the rule behind it and gives you a second case that most people answer the opposite way. A short Socratic walk into Joshua Knobe's famous 2003 finding, built so a whole classroom's verdicts can be gathered and compared.
Academician tier, or a class code from your instructor
Mary the Color ScientistA Thought Experiment, in Dialogue
Mary knows everything physical there is to know about color vision — and she has spent her whole life in a black and white room. When she walks out and sees a ripe tomato, will she learn anything? You give your answer, then a tutor draws out the argument hiding inside it and puts the classic pressure cases to you. A short Socratic introduction to Frank Jackson's knowledge argument, prompted by his 1982 paper "Epiphenomenal Qualia" — and to a question professional philosophers have never actually been polled on.
Academician tier, or a class code from your instructor
The side-effect effect
Knobe's 2003 finding and twenty years of follow-up experiments: cost-benefit reasoning, blame, deep-self concordance, norm violation, alternative possibilities, and a pragmatic account that aims to explain the effect.
Knobe (2003)Intentional Action and Side Effects in Ordinary Language
The side-effect effect — the most-cited result in experimental philosophy. Read one vignette, assigned at random, and say whether a chairman who is indifferent to the environment harmed (or helped) it intentionally. The two versions are matched on foresight, indifference and causal structure, and differ only in whether the side effect is bad or good; Knobe found 82% said the chairman intentionally harmed it vs 23% said he intentionally helped it. Both of his studies are included, and class results are compiled live against the published figures.
Runs on nat-hansen.com
Machery (2008)The Folk Concept of Intentional Action
A non-moral test of the side-effect effect. Read one randomly assigned smoothie-shop vignette and say whether Joe intentionally paid a dollar more (a cost) or intentionally got a free commemorative cup (a bonus) — then rate whether the outcome was blameworthy, praiseworthy, or neutral. Machery found 95% vs 45% 'intentional' with both outcomes judged morally neutral, evidence that cost-benefit reasoning, not morality, drives the asymmetry. Class results compiled live against the published figures.
Runs on nat-hansen.com
Pettit & Knobe (2009)The Pervasive Impact of Moral Judgment
Does the moral asymmetry reach beyond 'intentionally'? Read one randomly assigned version of the chairman case and rate, 1–7, whether he 'decided' to help or harm the environment. Pettit & Knobe found stronger agreement that he 'decided' to do it in the harm version (4.6 vs 2.7) — the same asymmetry for an ordinary mental-state word, evidence that moral judgment is a pervasive input to folk psychology. Class results compiled live against the published figures.
Runs on nat-hansen.com
Sripada (2010)The Deep Self and Asymmetries in Intentional Action
The badness of an outcome, or its fit with who the agent is? Read one randomly assigned, morally neutral rifle-contest vignette — one where the winner has no real stake, one where winning fulfils a lifelong dream — and rate whether the hit was intentional. Sripada found people call the outcome intentional far more when it concords with the agent's settled values, independent of moral valence. Class results compiled live against the published figures.
Runs on nat-hansen.com
Uttich & Lombrozo (2010)Norms Inform Mental State Ascriptions
Moral badness, or norm-breaking as such? Read one randomly assigned Gizmo-company vignette where a foreseen side effect either conforms to or violates a norm — sometimes a moral norm, sometimes a mere color convention — and rate, 1–7, how apt it is to call it intentional. Uttich & Lombrozo found norm-violating outcomes rated more intentional even for conventional norms, evidence that norm violation, not moral valence, carries the effect. Class results compiled live against the published figures.
Runs on nat-hansen.com
Nadelhoffer (2006)Bad Acts, Blameworthy Agents, and Intentional Actions
Does blame bias our judgments of what a person did on purpose? Read one randomly assigned version of a fatal car-swerve case — a fleeing thief killing a pursuing police officer, or an innocent driver killing an armed carjacker — and say whether the death was brought about knowingly, intentionally, and how much blame it deserves. A built-in lesson in experimental design: the two versions differ in more than one way at once. Class results compiled live against the published figures.
Runs on nat-hansen.com
Phillips, Luguri & Knobe (2015)Unifying Morality's Influence: The Relevance of Alternative Possibilities
Why does morality change judgments that aren't about morality? Read one randomly assigned version of the chairman case, then rate both whether he acted intentionally and whether a bystander's alternative was relevant. The claim: morality shapes which alternative possibilities strike us as relevant, and that is what moves the intentionality verdict — unifying the side-effect effect with parallel effects on causation and freedom. Your class's two measures are compiled live against the published figures.
Runs on nat-hansen.com
Lindauer & Southwood (2021)How to Cancel the Knobe Effect
Can the side-effect effect be switched off? Read one randomly assigned version of the chairman case and rate your agreement that he did NOT do it intentionally — except one group can also register strong condemnation in the same breath (“…but he knowingly harmed it and should be blamed”). When that option is present, the asymmetry collapses: the survey evidence its authors read as support for the pragmatic account. Compiled live against the published figures.
Runs on nat-hansen.com
Color and color language
Does the vocabulary you have shape what you see and remember? Experiments here play out the universals debate from both sides by looking at naming, memory, discrimination, and category boundaries, plus what color-blind experience is like.
Select & TranslateHow Color Models Carve Up Color Space Differently
An interactive illustration of how different color models represent color space. Select a region of one color model (RGB, HSL, CIELAB, or the 330-chip Berlin–Kay Munsell array) and see the same set of colors plotted in another. A continuous selection in one geometry shows up in another as a warped, sometimes scattered blob (what is continuous in one model is gerrymandered in another).
No sign-in; nothing is recorded
Berlin & Kay (1969)Basic Color Terms: Mapping the Munsell Array
The procedure that launched the universals debate, on the 330-chip World Color Survey Munsell array. List the basic color words of a language you speak, mark every chip each word covers, and pick its single best example. Berlin & Kay found that boundaries wander but foci cluster in the same regions across twenty languages; Roberson, Davies & Davidoff's Berinmo work pushed back. The instructor dashboard lays the class's charts on top of each other, focal points and term regions compared across whatever languages are in the room.
Runs on nat-hansen.com
Roberson, Davies & Davidoff (2000)Color Categories Are Not Universal: The Triad Task
The double-dissociation test. See three color chips at a time and click the two that look most alike — one set spans the English green–blue boundary, the other spans the boundary Berinmo (five basic color terms, Papua New Guinea) draws between nol and wor, straight through English green. Roberson et al. found each group's similarity judgments snapped to its own language's boundary and sat at chance on the other's: English speakers 23.0 vs 14.38 of 32, Berinmo 20.75 vs 25.38. The class runs the English arm against the published Berinmo numbers.
Runs on nat-hansen.com
Winawer et al. (2007)Russian Blues and Color Discrimination
Does the vocabulary you have change how fast you can tell two colors apart? A speeded matching task on twenty blues spanning the Russian siniy/goluboy border, which English does not mark: pick which of two squares matches the one above, sometimes while rehearsing an eight-digit number, sometimes while holding a grid pattern in mind. Russian speakers were 124 ms faster across the border than within it — and verbal, but not spatial, interference wiped that out. The class runs the paper's English-speaker arm, where the predicted result is a flat line.
Runs on nat-hansen.com
Brown & Lenneberg (1954)Codability and Color Memory
A classroom replication of the codability-and-memory study: name 12 colors, then try to recognise a subset after a 30-second arithmetic-filled delay. Anonymous results are compiled live for discussion.
Runs on nat-hansen.com
Heider — Focal Colors (1972)Universals in Color Naming and Memory
Rosch Heider's challenge to Brown & Lenneberg. Pick best examples of basic color names, name 12 chips (focal, internominal, boundary), then recognise a subset from an 80-chip array — testing whether codability drives memory or some colors are simply more distinctive.
Runs on nat-hansen.com
Inspired by Allen, Quinlan, Andow & Fischer (2021)What Is It Like to Be Colour-Blind?
What do you think a red/green color-blind person sees when they look at something red? Choose between four rival philosophical accounts, name six patches run through a standard simulation of color blindness, and predict which colors would look new through 'color-correcting' glasses. Allen et al. interviewed 17 color-blind participants: all of them named the red patch red, 12 of 17 saw no new colors through the glasses, and nobody saw red or green for the first time — every candidate new color was a pink or a purple. An original classroom design built on the paper's question, not a replication of its interview method. Class results compiled live against the published findings.
Runs on nat-hansen.com
Meaning, convention and conceptual change
Where meanings come from and how they shift: how conventions form between two players, how vocabulary drifts across a chain of learners, and two studies of what our words for truth and for terms like 'racist' currently pick out.
Lewis — Signaling GameConvention (1969)
Lewis's coordination problem, played by two people. One player sees a world state and sends one of four signals; the other sees only the signal and must guess the state. The signals start out meaningless and nothing is agreed in advance — so any shared meaning has to be built out of repeated play, from a run of lucky guesses into a regularity both players expect the other to stick to. Create a room, send the code to a partner, and watch a convention come into existence (or fail to).
Two players, two devices · Runs on nat-hansen.com
Esper (1966)Social Transmission of an Artificial Language
A live, in-class transmission chain. Each student learns names for eight shape-color objects, then reproduces them from memory — and their version becomes the language taught to the next student. Across generations a 'totally suppletive' vocabulary drifts toward morphological categories. Run several parallel chains and compare how they diverge. Instructors: open the room from the host console.
Run in class; instructor opens the room · Runs on nat-hansen.com
Reuter & Brun (2022)Empirical Studies on Truth and the Project of Re-engineering Truth
Is 'true' ambiguous? A three-part replication: read a story where a speaker's answer fits everything they believe but not the facts, then one where it fits the facts but not their beliefs, and say whether each answer was true. A third part runs the paper's checks on whether 'true' really just meant truthful. Reuter & Brun found responses split close to 50/50 — evidence that everyday 'true' has both a correspondence and a coherence sense.
Runs on nat-hansen.com
Based on McGrath & Haslam (2020) · Tse & Haslam (2023)The Harm Concept Breadth Scale & the Concept Breadth Scales
How broad are your concepts of trauma and mental disorder? Based on two of the experimental probes Haslam's team built to measure 'concept creep', plus a manipulation designed to test how our judgments shift when the target words appear in complex phrases.
Runs on nat-hansen.com
Hansen & Liao (2026)Measuring Conceptual Inflation
A classroom replication of Study 1 on the meaning of 'racist'. Rate the extension and intensity of 'racist', its degree-modified forms, related vocabulary, and a set of thin moral terms — then compare your live audience's pattern with the published representative-sample results.
Runs on nat-hansen.com
Belief and acceptance
Is understanding a proposition already to believe it? Testing the Spinozan hypothesis.
Gilbert, Krull & Malone (1990)Unbelieving the Unbelievable
A replication of Study 1: learn an invented Hopi vocabulary, get interrupted by an occasional tone, then take the identification test. The diagnostic asymmetry — false propositions misidentified as true under interruption — is what Spinoza predicts and Descartes does not. (From the Speech Attacks readings.)
Runs on nat-hansen.com
Distributive justice
Rawls's thought experiment and then the study that put it to real people: what they actually choose behind a veil of ignorance, when there is a specified amount of money at issue.
The Original Position, 1971Decide on a principle of justice to govern 1971 America
Step behind the veil of ignorance. Pick a tax-and-transfer principle, then observe five randomly drawn lives: a Detroit autoworker, a Greenwich attorney's wife, a Navajo uranium miner, and more. See how your principle affects their lives, commit to a principle, and see which life you have been assigned. You will get a feel for people's anxieties, hopes, and what difference a few thousand dollars makes.
Academician tier, or a class code from your instructor
Frohlich, Oppenheimer & Eavey (1987)Choices of Principles of Distributive Justice
A solo playtest of the classic veil-of-ignorance experiment. Pick a principle, see what you'd earn, then deliberate with four simulated co-participants and try to reach unanimous agreement. The original study found 35 of 44 groups chose a principle Rawls explicitly rejected.
Runs on nat-hansen.com