Sales Psychology & Ethical PersuasionCialdini's principles, applied ethically · Lesson 5 of 14

Authority, liking, scarcity and unity

Article · 14 min · 9 min lecture

Video lecture

Authority, liking, scarcity and unity

12 chapters · about 9 min · full transcript

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Chapter 1 of 12

Authority, liking, scarcity, unity

  • How each works
  • Ethical use and red lines
  • Evidence and current rules
  • A claims register

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Chapters

Four more principles

This lesson covers the remaining principles — authority, liking, scarcity and unity — with ethical applications and red lines.

4. Authority

What it is: people tend to follow credible experts.

Ethical use: demonstrate genuine expertise and cite credible sources accurately.

  • Share how you tested a product, your relevant qualifications or experience.
  • Reference genuine expert guidance (for example, a dermatologist's general advice on sunscreen) accurately and in context.
  • Be clear about the limits of your expertise: "I'm not a doctor — if you have a skin condition, see one."

Where it crosses the line:

  • Claiming credentials you don't have, or wearing a lab coat to imply medical authority.
  • "Doctors recommend" or "clinically proven" without substantiation.
  • Presenting paid experts as independent without disclosure.

5. Liking

What it is: people are more easily influenced by people they like — those who are similar, friendly, complimentary and cooperative.

Ethical use: be genuinely yourself, find real common ground, be warm and helpful.

  • Share relatable experiences and your real personality.
  • Engage personally with your community.
  • Compliment sincerely — never as a tactic.

Where it crosses the line:

  • Faking similarity ("I'm also a struggling student!" when you're not).
  • Love-bombing: excessive flattery to lower defences before a pitch.
  • Using parasocial relationships to pressure: "If you really supported me, you'd buy this."

6. Scarcity

What it is: things seem more valuable when they're rare, limited or at risk of being lost.

Ethical use: communicate genuine limits clearly — real stock limits, real deadlines, seasonal availability.

  • "The brand's Eid discount ends Friday at midnight Gulf time."
  • "This is a limited-edition run — the brand has confirmed no restock."

Where it crosses the line:

  • Fake countdown timers and "only 2 left" when untrue — widely treated as misleading by regulators, including the UK CMA, the US FTC and EU consumer authorities.
  • "Price goes up tomorrow" when it doesn't.
  • Creating panic to stop people comparing options.

Framing tip: loss framing ("don't miss out") is more intense than gain framing ("get this benefit"). Use loss framing sparingly and only when the loss is real.

7. Unity

What it is: people are influenced by those they see as part of a shared identity — "one of us" — such as family, community, region, faith or a shared passion.

Ethical use: build genuine community around shared values and interests.

  • A modest-fashion community sharing styling ideas for Eid.
  • A local creator championing businesses from their city.
  • A running community where members encourage each other.

Where it crosses the line:

  • Exploiting identity to shut down scrutiny: "Real Muslims / real Pakistanis / true fans buy this."
  • Using religious or national sentiment to sell products with no genuine connection to it.
  • Creating "us vs. them" hostility towards competitors or critics.

Identity-based appeals are powerful and sensitive — especially around faith and nationality. Use them only when the connection is genuine and respectful.

Putting it together: an ethical campaign example

A UK-based Pakistani creator promotes a halal-certified skincare brand to her community:

  • Authority: she shares the certification details and her testing process; she notes she isn't a dermatologist.
  • Liking: she films in her real bathroom, sharing her own routine.
  • Scarcity: she mentions the brand's genuine launch discount, with the actual end date.
  • Unity: she speaks to her community's genuine desire for halal-certified options — without implying anyone who doesn't buy is less devout.

Every principle is at work; every one passes the truth, transparency, benefit and freedom tests.

Do and don't

Do show real expertise and its limits. Do be genuinely yourself. Do communicate real deadlines and stock limits. Do build genuine community.

Don't fake credentials, similarity or scarcity. Don't use parasocial guilt. Don't weaponise faith or national identity.

Evidence notes

  • Authority: Milgram's obedience experiments (1960s) are often cited to show deference to authority; they're influential but debated (including critiques of how the studies were run and reported), and they're about obedience, not buying. For sellers, the practical point is simpler and uncontroversial: people rely on credible expertise, so fake credentials are especially harmful.
  • Scarcity: a classic 1975 study (Worchel, Lee and Adewole) found that cookies from a nearly empty jar were rated more desirable than identical cookies from a full jar. Scarcity effects are widely observed, but regulators specifically target false scarcity, and fake urgency is one of the most commonly cited dark patterns.
  • Liking and unity: similarity and shared identity reliably increase trust; they are also the principles most easily abused through parasocial pressure and identity politics.

Current rules on scarcity and urgency

  • UK: the CMA's consumer-enforcement powers (since April 2025) cover misleading urgency and pressure selling; it opened its first investigations under those powers in November 2025, including into online pricing practices.
  • EU: the UCPD blacklist includes falsely stating that a product will only be available for a very limited time to elicit an immediate decision.
  • US: the FTC's 2022 dark-patterns report lists fake countdown timers and false low-stock messages as deceptive.

Hands-on: an authority and scarcity claims register

Keep a simple register for every campaign:

ClaimTypeEvidence heldWho confirmedExpiry / review date
"Dermatologist-tested"AuthorityTest report ref., dateBrand regulatory teamRe-check each campaign
"Offer ends Friday 23:59 GST"Scarcity (time)Brief, section 3Brand manager (email)Friday
"Limited edition — 500 units"Scarcity (stock)Production confirmationBrandUntil sold out
"Used by 3 NHS trusts" (B2B)Authority/social proofClient permissions on fileLegalAnnual

If a claim has no evidence in the register, it doesn't go out.

Before and after: a unity appeal

Before: "Every proud Pakistani should support this brand — real patriots buy local!"

After: "This brand is made in Sialkot by a family business I've visited, and I love that. Here's what I like about the product and one thing I'd improve — buy it if it suits you."

The first uses identity to shut down scrutiny; the second shares a genuine connection and leaves the choice open.

Measuring

Track complaints mentioning "misleading", "fake" or "pressure"; refunds within the cooling-off period; and, for B2B, whether references and case studies are actually requested and used by buyers. Genuine authority and social proof get checked — and pass.

Key takeaways

  • Authority: show genuine expertise and its limits; never fake credentials or claims.
  • Liking: be authentic — no faked similarity, love-bombing or parasocial guilt.
  • Scarcity: communicate only real limits and deadlines.
  • Unity: build genuine community; never weaponise faith or identity.

Check your understanding

Quick questions to lock in the lesson. They don’t count towards your certificate.

  1. Which is an ethical use of scarcity?
  2. 'If you really supported me, you'd buy this.' Which principle is being misused?
  3. Which unity appeal crosses the line?

Put it into practice

Take one of your recent campaigns and write how each of the seven principles appears — then flag and fix any use that fails the four ethical tests.

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