● The principle library

Why people say yes, one card at a time.

14 principles from behavioural science, each with a plain definition, a real example and how to use it honestly.

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Anchoring

Decision stage

What it is: The first number people see becomes the reference point for every number after it.
Example: Show the annual price crossed out next to the monthly one, not after it.
Use it honestly: Lead your pricing with the most complete plan or a bigger cost the buyer already accepts.

Loss aversion

Action stage

What it is: A loss feels bigger than a gain of the same size, so people act to avoid losing.
Example: "Don't lose your saved cart" pulls harder than "Come back to your cart".
Use it honestly: Name what the reader keeps losing by not acting, without inventing urgency.

Scarcity

Action stage

What it is: Things that are rare or running out feel more valuable. It only works ethically when it is true.
Example: "20 seats per cohort" with a live, honest count.
Use it honestly: Explain the real reason supply is limited. Never fake a countdown.

Reciprocity

Interest stage

What it is: When someone gives us something useful first, we feel a pull to give something back.
Example: A free, genuinely useful checklist before you ask for an email.
Use it honestly: Give one piece of real value before you ask for anything.

Decoy effect

Decision stage

What it is: Adding a clearly worse option makes the option next to it look like the smart choice.
Example: A "Pro lite" plan priced close to Pro but with far less in it.
Use it honestly: Add a plan priced near your target with clearly less value, and honour it if bought.

Framing

Decision stage

What it is: The same fact, described differently, changes the choice people make.
Example: "95% uptime" and "down 1 day in 20" describe the same thing; they feel very different.
Use it honestly: Describe outcomes in the frame that matches what your buyer cares about.

Commitment and consistency

Action stage

What it is: After a small yes, people tend to stay consistent with it and say yes again.
Example: Ask one easy question before asking for the sign-up.
Use it honestly: Start with a small, easy step that leads naturally to the bigger one.

Authority

Interest stage

What it is: People lean on credible experts and signals of expertise when deciding.
Example: Show who wrote the guide and why they know, with a link.
Use it honestly: Show real credentials and sources. Borrowed or vague authority backfires.

Specificity

Attention stage

What it is: Concrete details are easier to picture and believe than vague promises.
Example: "Close your books in one afternoon" instead of "Save time on accounting".
Use it honestly: Swap adjectives for numbers, times and named results.

Curiosity gap

Attention stage

What it is: A small, honest gap between what people know and want to know makes them click.
Example: "The 3-word fix for cart abandonment" (and the article delivers it).
Use it honestly: Open a question your page actually answers. Clickbait breaks trust.

Endowed progress

Action stage

What it is: People are more likely to finish something when they feel they have already started.
Example: A checklist that starts at "1 of 8 done".
Use it honestly: Count the steps people have already done when you show their progress.

Default effect

Action stage

What it is: Most people keep whatever option is already selected, so defaults carry weight.
Example: Pre-select the plan most customers need, never a hidden add-on.
Use it honestly: Set defaults that are genuinely best for the customer.

Pattern interrupt

Attention stage

What it is: Something unexpected breaks autopilot scrolling and earns a second look.
Example: Open with a surprising true claim instead of the usual promise.
Use it honestly: Lead with the one true thing your reader doesn't expect.