Which mental models actually work, and which are just famous quotes?

What the badges and the myth label mean

Each row puts a claim you will see online next to what its source says. The last column gives the book's label.

The book uses three badges for tools. SOLID means tested on people more than once, or backed by a review of many studies, and it helps. PROMISING means real evidence that is thin or indirect. STORY ONLY means a real, documented habit that nobody has tested.

A fourth label, MYTH, is never given to a tool. It is given to the story told about a tool: a quote that was never said, or a number that does not mean what people think. That is why the pre-mortem row says MYTH for the 30 percent figure but PROMISING for the tool.

The incentive quote that is not in the talk

Start with the line on a thousand slides:

"Show me the incentive and I'll show you the outcome."

It is pinned to Charlie Munger, often to his 1995 Harvard talk, "The Psychology of Human Misjudgment."

The book searched both versions. The 1995 transcript and the 2005 rewrite in Poor Charlie's Almanack. Neither has that sentence. No primary source has turned up.

Munger did care about incentives. His real line, from the 2005 text, is this: "Never, ever, think about something else when you should be thinking about the power of incentives." It is a good line. It is just not the one people quote.

The idea itself holds up well. In a day-care study in Haifa, a small fine for picking children up late roughly doubled late pickups. Before, being late was a favor asked of a teacher. After, it was extra time you could buy, and cheaply.

It is late, and the twelfth list says the same things

You have read the posts. Fifty models. Ninety models. A latticework. Each one comes with a billionaire's name and a neat quote.

You tried a few. Some helped once. You cannot tell which ones are real and which ones just sound smart.

Here is the thing nobody says. Many of those lists copy each other, and each copy sands off a detail and adds a famous name. After enough rounds, nobody knows where a tool came from or if it does anything.

The tested ones are the boring ones

When the book sorted 40 tools, the count was 6 SOLID, 20 PROMISING and 14 STORY ONLY. Some famous tools landed low. Bezos's doors and Munger's circle of competence are both STORY ONLY. A track record is not a test.

Some plain tools landed high. Asking yourself why you might be wrong, then stopping at three reasons, worked across many separate experiments. Writing down an if-then plan ahead of time, "if this happens, then do that," has been tested in hundreds.

So if you only build two habits, we would start there. They are not exciting. That is part of why they get skipped.

The six SOLID tools, in one place

Most lists of mental models never say which ones were tested. Here are the six that earned the book's SOLID badge, with the small first step the book's 30-day plan gives each one.

The book's plan puts these in the last week on purpose. The month starts with easy, low-stakes STORY ONLY tools and ends with the habits most worth keeping. Its last step is one question: which SOLID habit will you keep, and when, exactly, will you use it?

Where the book sorts the rest

This is the problem Mental Models That Actually Work was written for. Ada Fenwick traced each of 40 tools to its letter, talk, book or study, and every chapter ends with a myth check.

How to Use This Book explains the badges and gives the full count, including why STORY ONLY does not mean useless.

Consider the Opposite is the strongest single habit in the book, with the studies behind it and the limit that keeps it from backfiring.

Incentives: Who Gets Paid If This Happens? has the full Munger story, the Haifa fine and a ten-minute Incentive Check that includes a line for you.

The Decision Selector and the 30-Day Plan has all 40 tools in one table with their badges, so you can see the whole sort at a glance.