01
The cognitive bias field guide
Pitfalls in individual thinking: what one mind does to itself, from attention and memory to how it judges other people.
Pursuits / Inspirations / Introduction to the field guides
Field guides to how thinking goes wrong
Three catalogues of the ways reasoning fails — inside one mind, inside a group, and inside a discussion. 640 named entries, each with what stands behind it and what it looks like in a school or a product team.
All inspirations
Why the guides exist
Three literatures that do not read each other
The literature on how thinking fails is large and it is scattered across fields that do not read each other. Cognitive psychology names what goes wrong inside one head. Social and organisational psychology name what happens to a judgement once a group forms around it. Informal logic and rhetoric name the moves that derail an exchange. Anyone who wants the whole picture has to hold three literatures at once, and most of us meet the material the other way — a name dropped in a meeting, a post online, a study half-remembered and probably misreported.
These three guides consolidate it into one place and one form. Each takes one of those bodies of work and sets it out as a catalogue: the name as the field gives it, what it is, what stands behind it, and what it looks like where I work. The point is not to memorise six hundred names. It is to have something to check against — the failures worth knowing about are exactly the ones that feel like clear thinking while they are happening, and a blindspot is not visible from inside the eye that has it. Read with one of these open, a decision gets a second pass it would not otherwise have had.
1
Name it as the field names it
Every entry uses the name the literature uses, with a definition short enough to hold in mind. Where two names describe the same thing, or one name has drifted to mean two, the entry says so rather than picking a winner quietly.
2
Say what stands behind it
Each entry carries its provenance: the founding study where there is one, and a plain statement where there is not. An entry resting on nothing more than repetition is marked that way and kept, because knowing a popular name is thin is worth as much as knowing a solid one is solid.
3
Put it where the reader works
Every entry lands in education. The first volume gives each bias a section on what it means for learning and one on what it means for a learning product; the second says where the fallacy lands in a school; the third supplies a reply that can actually be said in the room.
Who it is for
Everyone, with examples from one corner of the world
There is no reader model in these guides, and that is deliberate. The two series on the work side sort their advice by who is holding it, because a ministry officer, a vendor and a school lead each control a different part of a product. Nothing here works that way. A bias operates the same on a teacher, a procurement officer and a person choosing lunch, and a discussion goes wrong by the same moves whoever is in the room.
What is particular is the examples. I work on educational technology inside a school system, so that is where the illustrations come from: the pilot that looked successful because the keen schools volunteered, the committee that agreed before anyone had disagreed, the argument about screen time that never stated the claim it was defending. The reasoning carries anywhere. The cases are the ones I can vouch for, and I would rather a reader outside education did a small translation than have me invent situations I have not been in.
Inside a guide
One file, one entry shape, two ways to read it
Each volume sets every one of its entries in the same sections, so a reader who learns the shape once can use all three. The sections differ between volumes because the three kinds of fault need different things said about them.
| Volume | What an entry carries |
|---|---|
| 01 · Cognitive bias | What is it · Why it matters · In practice · How to counter · Relevance to learning · Application to edtech · Where it came from |
| 02 · Collective fallacies | What it is · Why it matters · The documented case · How to recognise it early · What works against it · Where this lands in education |
| 03 · Faulty arguments | The move · Where it breaks · The legitimate version · In the wild · What to say back · Where it came from |
- Slides
- Present a family in a room, or walk one entry through on a screen. Every entry has a Read more panel that opens the full treatment without leaving the slide.
- Reading
- Press R for the reading version: one continuous reference, with the families in order, the appendices — Appendix A is an A to Z index of every entry — and the full reference list. This is the version to search.
- One file
- Each volume is a single HTML file that works offline and prints. Deck, reading version and appendices come from the same content, so a correction made once appears in all of them.
What each volume contains
Three volumes, in the order the trouble arrives
One mind, one group, one exchange. The three are built on one engine and meant to be read together: a bias is something that happens to you, a collective fallacy is something a structure does to everyone in it, and a faulty argument is a move somebody makes. Nothing is repeated between them. Each opens as a deck; press R for the reading version, where Appendix A is an A to Z index of every entry, so a name you already have takes one click to find.
A set of three
The field guides
3 volumes
02
The collective fallacies field guide
Pitfalls in collective interaction: what happens to reasoning once more than one mind is involved.
03
The faulty arguments field guide
Pitfalls in collective decision making: the moves that derail a discussion, and what to say back.
How the guides were designed
The decisions behind them, and what each one costs
01Comprehensive before selective
Decision
Each volume tries to hold everything its field has named, rather than the dozen entries that would make a good talk. Six hundred and forty entries across three volumes, with the long tail kept.
Why
A shortlist is someone’s taste wearing the clothes of a reference. The value of a catalogue is that the entry you need is in it — and the one you need is rarely the famous one, because the famous ones are the ones you already watch for.
Trade-off
Nobody reads these front to back, and they are too long to. They are built to be looked up rather than read, which is why the index, the search and the glossary matter more here than in anything else on this site.
02Every entry says what stands behind it
Decision
Each entry is tagged with its provenance — the founding study, a body of observation, or an honest note that there is no single study and the name rests on usage.
Why
I kept collecting these because I wanted to know how many would survive being looked at properly. A good number do not. Replication has been unkind to parts of this literature, and a catalogue that hid that would be doing the same thing it is warning about.
Trade-off
Some well-loved names come out looking thin, which reads as debunking when it is only reporting. The entries stay in either way: a name in wide use is worth knowing even when the evidence under it is not much.
03Three volumes rather than one
Decision
The material is split by where the fault sits: in one mind, in a group, or in an exchange between people. Nothing is repeated between the volumes.
Why
They are different kinds of thing and they are fixed by different means. A bias is something that happens to you and is countered by design. A collective fallacy is something a structure does to everyone inside it and is countered by changing the structure. A faulty argument is a move somebody makes and is countered by answering it.
Trade-off
A few names could sit in two volumes, and one or two arguably should. Where that happens the entry goes where the remedy is, and the other volume points at it.
04The examples come from education
Decision
Every entry is worked through a case from teaching, schooling or educational technology rather than the finance and politics examples the sources tend to use.
Why
An abstraction does not transfer until it has been seen doing something. Education is the domain I can write about without guessing, and it is the domain the rest of this site is about.
Trade-off
A reader from another field has to translate. That is a real cost, and the alternative — generic examples about coins and urns — costs more, because nobody recognises themselves in them.
The vocabulary
Every name in the three, in one A to Z
640 entries from the three volumes as one list, each with the line its entry opens with and a link that opens the guide at it. A name that two guides share appears once for each, because each treats it differently.
The field guides glossary cognitive bias field guide collective fallacies field guide faulty arguments field guide
Field guides to how thinking goes wrong · Three volumes · 640 entries · September 2026
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