L0 - Foundations

Everyone is an amateur psychologist. You spend your whole day reading other people: guessing what a customer wants, what a colleague meant, why a voter stayed home. You have a working theory of human nature whether you have ever named it or not. The trouble is that these intuitions feel obviously correct and are often wrong, and the same goes for a great deal of what gets sold as behavioural expertise, the confident "studies show" claim, the viral bit of pop psychology, the consultant's neat framework. Some of it is solid. A surprising amount of it is not.

This layer is where you learn to tell the difference. It does not hand you findings about how people behave; the later layers do that. Instead it gives you the ground rules for knowing anything about people at all. What actually counts as evidence? Why does a single striking study rarely settle a question? What is an effect size, and why does it matter that an effect is real but tiny? Why is the gap between what people say and what they do so wide, and so easy to be fooled by? These are the questions a scientist asks before believing a result, and they are exactly the questions a practitioner needs in order not to be taken in.

Why this matters to you

If your work involves influencing other people, and almost all business and policy work does, you are already swimming in behavioural claims. Every deck, every campaign proposal, every management book leans on some assertion about what makes humans tick. Most of the people making those claims cannot tell you how good the evidence behind them is, because they have never had to. That is the blind spot this whole project exists to close, and this layer is the part that closes it most directly. What you get here is not a fact to deploy but a filter to think with: a way to read a behavioural claim and ask, quietly, how sure should I really be about this before I bet money or policy on it?

That filter turns out to be one of the most valuable things science can give a non-scientist. It is the difference between chasing whatever idea is fashionable this quarter and knowing which ideas have earned their confidence.

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What you'll find inside

The pieces in this layer are the recurring ways that studying people goes wrong, and how researchers try to get it right anyway. You will meet the say-do gap, the well-documented fact that what people tell you they will do is a poor guide to what they actually do. You will see why people genuinely cannot tell you the real reasons for their own choices, so asking them directly can mislead you. You will get an honest tour of the replication crisis, the moment when a chunk of famous psychology turned out not to hold up when other scientists tried to repeat it, and what survived it. You will learn why every way of measuring people distorts something, so the smart move is to triangulate rather than trust one number. And you will look at two old arguments that shape everything downstream: how much behaviour is driven by the person versus the situation they are in, and whether a citizen making a choice is really just a consumer by another name.

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The honest note

Every layer in this guide ends on a caveat, because the caveats are often the most practical part, and this layer sets the tone for all of them. The honest headline of the foundations is this: treat behavioural findings as provisional, not gospel. Real effects are frequently smaller and more fragile than the confident version you first heard. Context changes results. Good evidence accumulates slowly, across many studies, rather than arriving in one dramatic paper. None of this is a reason for cynicism, and it is certainly not a reason to throw up your hands and trust your gut instead, because your gut is exactly what this science keeps catching out. It is a reason for calibrated confidence: believing solid things firmly, shaky things loosely, and always knowing which is which. Get that habit from this layer and everything that follows will land better, and mislead you less.