This is the whole course in one sitting. Hold the through-line in your head: in most of the universe the arrow points one way — facts drive beliefs, and a rock falls at 9.8 m/s2 no matter what you think of it. But in the social world — banks, markets, reputations, regimes, relationships — beliefs reach back up the arrow and bend the very reality they were supposed to be merely reporting. That is reflexivity, and its sharpest engine is the coupling threshold: a loop stays idle until enough people act on a belief, and then it ignites — the same rumour that fades on a quiet day becomes true on a jittery one. A prophecy that reinforces itself comes true (the bank run); a prophecy that undermines itself erases itself (the emptied road). And because a model you cannot criticise is a superstition, we finish with exactly where the model lies. Take a breath. There is no going back once you commit.
How this exam works
This is a real exam, not a practice quiz. Questions appear one at a time. Once you submit an answer it is locked for good — there is no going back, no retry, and no restart. Your score stays hidden until the very end. A few questions ask you to select all that apply (read those carefully — partial credit is not a thing here). You need 70% to pass. Ready when you are.
Robert Merton coined the SELF-FULFILLING PROPHECY. Which statement captures its definition most precisely?
Select an answer to continue.
Big picture
Reflexivity & self-fulfilling dynamics, in one picture
- Reflexivity & self-fulfilling dynamics
- The self-fulfilling prophecy
- Merton: a FALSE belief becomes true because people act on it. The Thomas theorem - if people define situations as real, they are real in their consequences. The bank run: fractional reserve means a solvent bank cannot pay everyone at once, so fear drains the vault and CAUSES the failure. A critical-mass threshold decides fizzle vs sweep; Diamond-Dybvig show TWO equilibria (calm survives, run fails) for the same solvent bank
- The self-defeating prophecy
- The mirror image: a forecast that, believed and acted on, triggers the response that FALSIFIES it. The jam warning empties the road; the public tip prices itself out. The prevention paradox - a warning that works averts the disaster and gets mislabelled a false alarm, eroding trust. The SIGN of the loop decides everything: reinforcing loops fulfil, balancing loops defeat
- Reflexivity in markets
- Soros: a cognitive function (read the market) and a manipulative/participating function (your actions change it) feed back. Price is not a cool readout - a rising price improves the fundamentals (cheap capital, acquisitions) which justifies a higher price. Booms and busts are the reinforcing loop overshooting then reversing violently. Currency pegs break under self-fulfilling speculative attack (multiple equilibria). The market can stay irrational longer than you can stay solvent
- Reflexivity in the social world
- Pygmalion/Rosenthal: a teacher's (random) expectation lifts a pupil's REAL performance; the Golem effect does the reverse; stereotype threat is a contested cousin. Placebo and nocebo - belief bends physiology. A credit rating or a reputation for confidence changes the very creditworthiness it grades - the magic thermometer cooling the room it calls cold
- Belief loops vs ordinary feedback
- What makes a loop REFLEXIVE is that it passes through beliefs and expectations - which turns information, narrative and even a forecast into causes. Ordinary feedback needs no minds: a thermostat, predator-prey cycles. A weather forecast is non-reflexive (predicting rain cannot make it rain); a recession forecast IS reflexive (it makes firms cut). The observer sits inside the system
- Where the model lies
- Not everything is reflexive - gravity is exogenous, 9.8 m/s2 no matter what you think. "It's reflexive" is an unfalsifiable story unless you name the MECHANISM (which belief, whose actions, what return channel). Reflexivity vs mere correlation needs the RETURN arrow - belief actually causing the reality. Loops are hard to predict and reverse violently; and engineering self-fulfilling confidence shades into recklessness and fraud
- The self-fulfilling prophecy
Key takeaways
You now hold the whole model. In most of the universe the arrow runs one way — facts drive beliefs, and a rock falls at 9.8 m/s2 whatever you think of it. Reflexivity is the social exception, where beliefs reach back and bend the very reality they were meant to report. Its sharpest engine is the self-fulfilling prophecy (Merton): a false belief becomes true because people act on it — the Thomas theorem, “if people define situations as real, they are real in their consequences.” The archetype is the bank run: fractional-reserve banking means a solvent bank cannot pay everyone at once, so fear drains the vault and causes the failure, once withdrawals cross a critical-mass threshold — and Diamond–Dybvig prove the same solvent bank has two equilibria (calm survives, run fails), settled purely by coordination. Flip the loop’s sign and you get the self-defeating (suicidal) prophecy: the jam warning that empties the road, the tip that prices itself out, and the prevention paradox where a warning that works looks like a false alarm — reinforcing loops fulfil, balancing loops defeat. In markets this is Soros: a cognitive function (read the market) and a manipulative/participating function (your action changes it) that feed back, so a price is no cool readout — a rising price improves the fundamentals that justify a higher price, and booms and busts are the reinforcing loop overshooting then reversing hard (the market can stay irrational longer than you can stay solvent); currency pegs break under self-fulfilling speculative attack. In the social world it is Pygmalion (and the Golem effect), the placebo and nocebo, and the credit rating that changes the creditworthiness it grades. What makes a loop reflexive rather than ordinary feedback is that it passes through beliefs and expectations — turning narrative and forecasts into causes — which is why a thermostat and a weather forecast are not reflexive but a recession forecast is. And the model lies at its edges: not everything is reflexive (gravity is exogenous), “it’s reflexive” is an unfalsifiable story unless you can name the mechanism, reflexivity needs the return arrow that mere correlation lacks, the loops are hard to predict and reverse violently, and engineering self-fulfilling confidence shades into recklessness and fraud. Never ask only “is this belief true?” Ask: does acting on it reach back and make it so?