Trust Is the Only Currency: They're Not Buying the Product, They're Buying "Can I Trust You?"

Mechanism: an evolutionary ordering — ask "friend or foe" before "strong or weak." Facing a stranger, the brain's top-priority question is "does this person mean me well or ill?" (warmth / intent), because getting that wrong can be fatal; only then does it ask "and do they have the ability to act on that intent?" (competence). So warmth is the entry ticket and competence is the amplifier: when warmth reads negative, more competence is scarier (they're able to harm you); when warmth reads positive, competence finally amplifies trust.

• Stereotype Content Model: Fiske, Cuddy & Glick (2007, Trends in Cognitive Sciences) — judgments of others fall along two universal dimensions, warmth and competence; warmth is judged faster and weighted more heavily in first impressions. Replicated cross-culturally — fairly hard evidence.
• Connect, then lead: Cuddy, Kohut & Neffinger (2013, Harvard Business Review) — people who project warmth before competence are more influential; leading with competence often backfires and invites wariness.
• Neuroscience · the amygdala "rules" on trust before you're aware: Willis & Todorov (2006, Psychological Science) — 100 milliseconds of a face is enough to form a trustworthiness judgment; longer exposure barely changes it, only firms up confidence. Engell, Haxby & Todorov (2007) — even when you're not asked to evaluate, amygdala activity automatically tracks a face's trustworthiness. The first gate of trust is automatic, fast, and pre-rational. (For this brain mechanism, see the neuroscience / psychology sites.)

Boundary: "warmth first" matters most on a first meeting, under low trust; in long-standing relationships where competence is already proven, the order matters less. The HBR piece is practitioner insight plus cases — weaker than the two academic findings around it.

Mechanism: credibility / reliability / intimacy resolve three uncertainties — what you say, what you do, what you hide. Self-orientation is the trust killer: the moment they sense you're only in it for yourself, they re-read everything you've said as "just tactics," and the numerator you built up gets divided down. Why is lowering self-orientation so potent? Because it's counterintuitive and a costly signal: someone who only wants the sale won't tell you not to buy — so when you do, you've flashed hard evidence that you really are looking out for them.

• The trust equation: Maister, Green & Galford, The Trusted Advisor (2000) — note: this is a widely adopted practitioner framework / consulting distillation, not a controlled experiment; its value is being usable and decomposable, and its evidential strength is experiential.
• Self-disclosure → liking (hard support for intimacy): Collins & Miller (1994, Psychological Bulletin) meta-analysis confirms that moderate, mutual self-disclosure reliably raises liking; Aron et al. (1997) famous "36 questions" study used escalating mutual disclosure to make two strangers feel close in 45 minutes. Fairly hard evidence.
• Costly signaling: evolutionary game theory — a signal is credible only when faking it is expensive. Volunteering the truth against your own interest (telling them not to buy, flagging your own risk) is exactly such a costly signal, so it builds trust unusually well.

Honestly labeled: the equation itself is a framework, not an experiment; but each of its four terms has harder psychological support (disclosure→liking, costly signaling, promise-keeping). Don't treat the formula as precise math — use it as a checklist.

Mechanism: negativity bias + loss aversion + the asymmetry of trust. The brain processes "bad" harder and longer than "good" (evolutionarily, missing one danger costs far more than missing one gain). So the trust lost from one betrayal isn't offset by one act of good faith; and "losing trust" is coded as a loss, which by loss aversion takes roughly twice the good to make up. That's the root of "slow to build, fast to break."

• "Bad is stronger than good": Baumeister, Bratslavsky, Finkenauer & Vohs (2001, Review of General Psychology) — a cross-domain review showing negative events systematically outweigh equivalent positive ones in emotion, memory, and relationships. Fairly hard (a review of many studies).
• Loss aversion: Kahneman & Tversky (1979, Prospect Theory) — the pain of an equivalent loss is about 2× the pleasure of the gain. Broken trust is registered as a loss, so it hurts and repairs especially hard. Nobel-level, classic.
• The asymmetry principle of trust: Slovic (1993, Risk Analysis), Perceived Risk, Trust, and Democracy — trust-destroying events are more visible, more believed, and weighted more heavily than trust-building ones; "easy to destroy, hard to build" is a measurable regularity, not just a feeling. Fairly hard.

Boundary: in small, low-risk, quickly re-verifiable settings, a collapse isn't as fatal (still recoverable); the bigger, longer-term, and harder-to-verify the relationship, the more savage this asymmetry.

Mechanism: repeated games + reliability lowering the other side's "cognitive cost." (1) Repeated games — in a one-shot deal betrayal might pay, but real relationships are played over and over: keeping faith wins across long iteration, while betrayal gets punished by reputation and no-repeat. (2) Lower cognitive cost — each time you keep a promise, they spend a little less effort checking you; accumulate enough and they set "you're reliable" as the default, and transaction friction drops sharply. That's the source of compounding: the audit cost they save becomes your premium and your speed.

• Cooperation wins in repeated games: Axelrod, The Evolution of Cooperation (1984) computer tournaments — a "start nice, keep your word, punish only when crossed" strategy beats every strategy that tries to profit by defecting. Classic, directionally hard.
• Trust lowers transaction cost: institutional economics (Williamson; and Fukuyama, Trust, 1995) — in high-trust relationships the cost of verifying, monitoring, and writing airtight contracts drops sharply, and that saved efficiency is trust's economic return. Theory + macro evidence, directionally aligned.
• Reliability = the compounding of commitment-consistency: same root as the reciprocity / repeated-game logic from Day 1; repeated "said and done" gets encoded as a stable expectation, and that's what makes trust roll up like interest.

Honestly: this one is more the combined weight of classic game theory + institutional economics + practitioner experience than any single randomized experiment; but the direction is broadly supported. Compounding requires a real, long-term, verifiable relationship — in one-shot, anonymous settings it barely happens.