Thinking Dictionary
Thinking Dictionary: the core ideas of scientific thinking
Plain-English explanations of the ideas behind good evidence, each with everyday examples and a try-it task.
Accuracy vs precision
When you measure something, two different questions matter.
Read entry →Concept · 02Actively open-minded thinking
Actively open-minded thinking is more than just "keeping an open mind." It means:
Read entry →Concept · 03Blinding
Blinding means keeping people in a study from knowing who got the real treatment and who got the comparison. If nobody knows, hopes and expectations can't tilt the results.
Read entry →Concept · 04Cherry-picking
Cherry-picking means showing only the evidence that supports a point and leaving out the rest. Imagine picking only the ripest cherries from a tree, then saying the whole tree looks like that.
Read entry →Concept · 05Cognitive shortcuts
Cognitive shortcuts, also called heuristics, are rules of thumb the brain uses to make quick judgements. They ignore some of the available information so we can decide fast. Most of the time they…
Read entry →Concept · 06Confirmation bias
Confirmation bias is our habit of looking for, trusting, and often remembering information that agrees with what we already believe. At the same time, we tend to overlook or explain away information…
Read entry →Concept · 07Confounding variable
A confounding variable, or confounder, is a hidden third factor that affects both of the things you are comparing. It can make two things look connected when they aren't. It can also hide a real…
Read entry →Concept · 08Correlation vs causation
A correlation means two things tend to go up or down together. Causation means that changing one thing actually changes the other.
Read entry →Concept · 09Credible sources
A credible source is one you have good reason to trust on the question in front of you. Three questions do most of the work:
Read entry →Concept · 10Error bars and confidence intervals
Many results are reported as a single number: "48% support the plan." But no measurement is perfectly exact. An error bar or a confidence interval shows the range where the true value probably lies.
Read entry →Concept · 11Facts vs values
A factual claim is a statement that could, at least in principle, be checked with evidence. It doesn't have to be true. "The Moon is made of cheese" is a factual claim. It is simply false.
Read entry →Concept · 12False positives and false negatives
Every test can be wrong in two different ways.
Read entry →Concept · 13Falsifiability
A claim is falsifiable if some possible observation could show that it is wrong. "All swans are white" is falsifiable: one black swan would sink it. "Everything happens for a reason" is not, because…
Read entry →Concept · 14Fast and slow thinking
We have two broad ways of thinking.
Read entry →Concept · 15Fermi estimation
A Fermi estimate is a quick, rough calculation that gets you into the right ballpark. You take a question that seems impossible to answer and break it into smaller pieces you can reasonably guess.…
Read entry →Concept · 16Indicators of causation
Indicators of causation are questions to ask before you believe a claim that "X causes Y." A practical way to use them is four questions, a simplified version of the epidemiologist Austin Bradford…
Read entry →Concept · 17Iteration
Iteration means improving an idea or a tool through repeated rounds. You try something, test it, find what went wrong, and change it. Then you go round again. In science, changing a conclusion when…
Read entry →Concept · 18Lateral reading
Lateral reading means judging a website or a post by checking what other sources say about it. "Lateral" means sideways. Instead of reading down the page, you move sideways: you open a new tab and…
Read entry →Concept · 19Misinformation vs disinformation
False information comes in different kinds. One widely used framework, written for the Council of Europe, sorts it by intent:
Read entry →Concept · 20Motivated reasoning
Motivated reasoning is reasoning that is steered by what we want to be true. When we want a particular conclusion, we tend to use whatever ways of thinking are likely to get us there. But there is a…
Read entry →Concept · 21Multiple lines of evidence
Multiple lines of evidence means supporting a conclusion with several different kinds of evidence. Each kind could go wrong, but in its own way. If they still all point to the same answer, the…
Read entry →Concept · 22Nocebo effect
The nocebo effect is the dark twin of the placebo effect. Expecting to feel bad can make you feel bad. Negative expectations can produce real, unpleasant symptoms.
Read entry →Concept · 23Peer review
Peer review is the step where other experts check a study before a scientific journal publishes it. These reviewers, the author's "peers," look for weaknesses in the methods, the analysis, and the…
Read entry →Concept · 24Placebo effect
A placebo is a fake treatment. It might be a sugar pill, an injection of salt water, or a pretend operation. It has nothing in it that acts on the problem.
Read entry →Concept · 25Probabilistic reasoning
Probabilistic reasoning means asking "how likely?" instead of "yes or no?" You consider several possible explanations. You give each one a rough probability, meaning how likely it is, based on the…
Read entry →Concept · 26Random vs systematic error
In science, an error is not necessarily a mistake. It is the unavoidable gap between a measurement and the true value. Errors come in two main kinds.
Read entry →Concept · 27Randomized controlled trial
A randomized controlled trial, often shortened to RCT, is a way of testing whether a treatment really works. The people taking part are split into groups by chance, as if by tossing a coin.
Read entry →Concept · 28Regression to the mean
Regression to the mean means that after an unusually high or low result, the next one is usually closer to average, even if nothing changed. "The mean" is just another word for the average.
Read entry →Concept · 29Reverse causation
Reverse causation is when we get the arrow backwards. Two things are linked, and it looks as if X causes Y. But really, Y causes X.
Read entry →Concept · 30Sample size
Sample size is how many people, animals, or measurements a study includes. Scientists often write it as n. A study "with n = 50" included 50 people or measurements.
Read entry →Concept · 31Scenario planning
Scenario planning means imagining several different ways the future could turn out, and then choosing actions that work reasonably well in most of them. You don't stake everything on one prediction.
Read entry →Concept · 32Scientific models
A scientific model is a simplified version of something that is too big, too small, too slow, or too complicated to study directly. A model can be a map, a diagram, an equation, or a computer program…
Read entry →Concept · 33Scientific uncertainty
Scientific uncertainty is an honest statement of how sure we are about something. Every scientific finding carries some uncertainty. But the amount varies hugely. Some conclusions are close to…
Read entry →Concept · 34Senses vs instruments
Our senses, such as sight, hearing, touch, and smell, are fast and useful. But they are limited, and they are easily fooled. Instruments, such as thermometers, scales, and satellites, can measure…
Read entry →Concept · 35Signal vs noise
The signal is the real change or pattern you care about. The noise is the random up-and-down that happens anyway. Almost every single measurement contains some of both. So one reading on its own…
Read entry →Concept · 36Simpson's paradox
Simpson's paradox is when combining groups flips a pattern. Something can be true in every group separately, yet look the opposite when all the groups are added together. It can also work the other…
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