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arXiv:2512.05998 ★ 86 Dec 1, 2025

Fake Prediction Markets: Bets as a Calibrated Signal of LLM Confidence

Key result

The problem: LLMs are terrible at showing confidence. Ask for "yes/no" and you get a mushy "most likely." Give a 1-10 scale and everything drifts to 7-8. The Prediction Markets method lets you extract the model's hidden confidence through a numeric signal — the size of the bet on each prediction. The trick: don't ask for a confidence percentage — make the model risk virtual money. Give it a bankroll of 1M coins and a stake range of 1-100k per prediction. The model can't bet the max on everything — it has to choose. Big bets of 40k+ turned out right 99% of the time, small ones <1k only 74%. Bet size = an indicator of real confidence.

01

TL;DR

Fake Prediction Markets is a technique that adds a betting mechanism to any model forecast or assessment: the model holds a virtual currency (say, 1M LLMCoin) and stakes between 1 and 100,000 coins on each of its answers. The stake reveals its degree of confidence — whale bets (40k+) turned out correct 99% of the time, small bets (<1k) only 74%. This turns a binary "yes/no" answer into a graded confidence scale with a numeric anchor.

LLMs usually give binary answers or verbal assessments ("probably," "most likely"), but their internal confidence stays hidden. You don't know how sure the model is about its "yes." The researchers tested this: three models predicted whether the answers of six other models to 100 math problems were correct. The control group gave a plain "correct/incorrect." The experimental group gave the same predictions plus a mandatory bet. Bet size correlated clearly with accuracy: the bigger the bet, the more often the model was right. Prediction accuracy itself rose only slightly (+2.4 percentage points, not statistically significant), but the learning speed quadrupled: in Incentive mode the models improved accuracy by 12 percentage points between round one and round four, versus 2.9 in the control group.

The gist of the method: you add financial framing to the task — a virtual bankroll, rules for winning/losing a bet, a goal of maximizing wealth. The model starts differentiating its confidence numerically: it bets big on "sure" predictions and pocket change on shaky ones. No changes to the model's weights — only the request format and the output change (a bet amount is attached to each answer).

Want this for your own case? Apply this study to your task: AI adapts its method to what you are working on and writes the prompt.

02

Method Blueprint

Control version (for comparison):

Task → Prediction: Yes/No → Result

Incentive version (with the betting mechanism):

START: Bankroll = 1,000,000 LLMCoin

FOR EACH TASK:
  1. Prediction: Correct/Incorrect
  2. Stake: from 1 to 100,000 coins
  3. Brief rationale (optional)

PAYOUT RULES:
  - Prediction right → +stake to bankroll
  - Prediction wrong → -stake from bankroll

CONSTRAINTS:
  - Total stakes in a round ≤ current bankroll
  - Bankroll < 1 coin = bankruptcy (game over)

AFTER EACH ROUND:
  - Feedback: which predictions were right
  - Statement: wins, losses, new balance

Everything happens in a single conversation with the model. Each task = one output with a prediction + a stake.

03

Example in Practice

⚠️ The method works best when you need to rank confidence across many assessments/forecasts, not get one correct assessment. It doesn't fit subjective creative tasks with no verifiable outcome.

Task: You have 20 edtech startup ideas. You want to know which directions to dig into — you need prioritization by confidence, not just a pros-and-cons list.

Prompt:

You are a venture analyst with a bankroll of 1,000,000 VCCoin.

Your task: for each idea on the list, predict whether it can raise a seed round of $2M+ from US VC funds in 2025.

Rules:
- For each idea, give a prediction: YES (will raise) or NO (won't raise)
- Attach a STAKE of 1 to 100,000 VCCoin to each prediction
- If the prediction is right, you win the stake
- If it's wrong, you lose the stake
- The sum of all stakes can't exceed your current bankroll
- Goal: maximize your final bankroll

Output format for each idea:
{
  "idea": "[name]",
  "prediction": "YES/NO",
  "stake": [number from 1 to 100000],
  "rationale": "[1 sentence]"
}

Here are the 20 ideas:
1. A corporate training platform with an AI assistant...
2. A mobile app for SAT prep...
[... the rest of the ideas]

After the predictions, show:
- The top 5 ideas with the biggest stakes
- The top 5 ideas with the smallest stakes
- The total amount staked

Result:

The model will return a JSON list with a prediction and a stake for each idea. The stake size shows the model's confidence: whale bets of 50k-100k coins go to ideas with obvious product-market fit and a clear business model (e.g., "corporate training with measurable ROI for HR"). Small bets of 100-5,000 coins go to highly uncertain ideas (e.g., "a gamified social network for high schoolers"). At the end you'll see a list ranked by confidence and can focus on the top, where the model "went all in."

You get not just an assessment of each idea but a numeric priority scale, grounded in the model's calibration. It works better than "rate on a 1-10 scale" because the stake is tied to the bankroll and risk — the model can't bet 100k on every idea, it has to choose.

04

Why It Works

The weakness: LLMs are bad at calibrating confidence in binary or verbal answers. "Most likely" and "probably" are fuzzy words. Even if you ask "rate your confidence 1-10," the model doesn't grasp the relative weight of scores within one request: everything may get 7-8.

The strength: LLMs are great at ranking and can work with numeric constraints when the constraints are explicit and tied to context. When the model has a finite resource (a bankroll) and explicit rules (win/lose the bet), it starts differentiating tasks by confidence.

How the method exploits this: The "maximize your bankroll" framing turns the task into a constrained optimization problem. The model can't put 100k coins on every prediction — it has to choose where confidence is high. The stake becomes a proxy for internal probability: if the model sees clear signs of correctness (e.g., an easy problem + a strong model), it bets big. If there's uncertainty, it bets pennies.

Bonus effect: The feedback mechanism through a numeric balance speeds up learning. After each round the model sees "+45,000" or "−12,000" — a brighter signal for the attention mechanism than a plain "wrong." In the study, models in Incentive mode improved accuracy by 12 percentage points between round one and round four, while the control group improved by only 2.9. A numeric loss/gain is louder to the model than verbal feedback.

Prompt control knobs:

  1. Bankroll size (1M → 100k or 10M) — changes the granularity of bets. A bigger bankroll = more room to differentiate.

  2. Stake range (1-100k → 1-1k or 1-1M) — affects how aggressively the model can express confidence. A narrow range = smaller gaps between "sure" and "not sure."

  3. Payout rules (even odds → different multipliers for different tasks) — you can make it trickier: "a bet on a hard task pays ×2." That forces the model to recompute the risk/reward ratio.

  4. Bankruptcy condition (remove it or replace with a "soft penalty") — drop the hard limit and the model gets bolder. Add "max stake = 10% of balance" and it gets more conservative.

  5. Feedback between rounds (balance only → balance + error breakdown) — a detailed "where and why you lost" review speeds up learning even more.

These knobs let you tune the sensitivity of the method to your task: want aggressive differentiation — widen the stake range; want safe ranking — add a per-bet cap.

05

Prompt Template

You are a {role, e.g.: expert/analyst/evaluator} with a bankroll of {number} {currency name, e.g.: AnalystCoin}.

Your task: for each {item being assessed: idea/forecast/option/solution} on the list, give a prediction {criterion: "will work/won't work", "correct/incorrect", "profitable/unprofitable"}.

Rules:
- For each item, give a prediction: {option A} or {option B}
- Attach a STAKE of {minimum, e.g.: 1} to {maximum, e.g.: 100000} {currency name} to each prediction
- If the prediction is right, you win the stake (added to your balance)
- If it's wrong, you lose the stake (subtracted from your balance)
- The sum of all stakes can't exceed your current bankroll
- Goal: maximize your final bankroll

Output format for each item:
{
  "name": "[item name]",
  "prediction": "{option A/option B}",
  "stake": [number],
  "rationale": "[1-2 sentences]"
}

Items to assess:
{paste your list of tasks/options/ideas}

After all predictions, show:
- The top 5 items with the biggest stakes (highest confidence)
- The top 5 items with the smallest stakes (low confidence)
- The total of all stakes
- The bankroll remaining after the bets

What to plug in: - {role} — the expert context (venture analyst, technical reviewer, editor) - {number} — starting bankroll, usually 1,000,000 or 100,000 - {currency name} — make up a name (VCCoin, EditorCoin, TechToken) — it creates game framing - {item being assessed} — what you're evaluating (startup ideas, code snippets, copy variants) - {criterion} — a binary criterion with a verifiable outcome (will work/won't work, has a bug/no bug) - {option A/B} — the two possible prediction outcomes - {minimum/maximum} — the stake range, usually 1–100,000 - {list} — the specific items to assess

06

Why the Structure Works

This isn't programming, it's framing. The LLM doesn't "execute code" — it follows game rules described in words. The betting mechanism is a structured instruction that creates:

  1. A numeric constraint (the bankroll) — the model is forced to rank tasks and can't hand everyone the max.

  2. An explicit notion of risk (win/lose the bet) — the model understands that a big bet = a big cost of being wrong.

  3. A feedback loop (balance updates) — a numeric change in the balance is louder to the model's attention than a verbal "wrong."

This structure turns the model's internal uncertainty into an explicit output — the stake size. Without bets the model generates "yes" or "no" with no gradations. With them it's "yes, and I'm betting 80k" vs "yes, but I'm only betting 500."

07

Limitations

⚠️ The arithmetic is unreliable: In three of nine experimental runs the models slightly exceeded the per-round stake limit (~0.2% overspend). Internal "bookkeeping" of wins/losses was correct, but planning the total stake glitched. If precise balance control matters, check the math outside the model (e.g., sum the stakes yourself or with a script).

⚠️ You need a verifiable criterion: The method works when there's an objective truth (a correct answer, a real-world outcome). For subjective assessments ("how creative is this text"), the model can't get "bet won/lost" feedback — calibration breaks down.

⚠️ Best for multiple assessments: If the task is a single assessment or forecast, the stake adds a confidence signal, but ranking won't work (nothing to compare). The method pays off most when you need to prioritize 10-100+ items.

⚠️ Doesn't boost accuracy much: In the study accuracy rose by +2.4 percentage points (79.1% → 81.5%, p = .089, not statistically significant). The main value isn't accuracy but calibration — you see where the model is confident (whale bets: 99% accuracy) and where it's in doubt (small bets: 74% accuracy).

08

How They Tested It

The researcher generated 100 math problems with algorithmically verifiable answers (divisibility, primes, modular arithmetic, linear equations) using GPT-5 Extended Thinking + verification code. That ruled out "guessing" from memorized training data.

Six Baseline models (three current-gen: Gemini 2.5 Pro, Claude Sonnet 4.5, DeepSeek R2; three prior-gen: Gemma 2 2B, Claude 3 Haiku, DeepSeek R1) solved all 100 problems. Current-gen models answered 93.3% correctly, prior-gen 52.3%.

Three Predictor models (Grok 4 Expert, Mistral Large 2 Thinking, Qwen 3 Max Thinking) predicted, for each (problem, Baseline) pair, whether the Baseline would answer correctly. That's 600 predictions per run (100 problems × 6 Baseline models).

Each Predictor model did three runs in the control group (plain "yes/no" predictions) and three in the Incentive group (prediction + a stake of 1 to 100k coins from a 1M bankroll). In total, 9 runs per condition = 5,400 predictions per group.

The problems were split into four rounds of 25 questions. After each round the Predictor got feedback: which Baseline models answered correctly. The Incentive group also saw an updated coin balance (how much it won/lost).

The results showed: - Accuracy in Incentive was slightly higher (81.5% vs 79.1%), but not statistically significant (p = .089). - Learning was 4× faster: Incentive models improved accuracy by 12 percentage points from round 1 to round 4, control models by only 2.9 (p = .011, a significant effect). - Whale bets were nearly flawless: stakes of ≥40k coins were right 98.8% of the time (168 of 170), small stakes <1k only 73.9%.

This showed that stake size is a clean calibration signal. The model "sorts" its predictions by confidence on its own via the financial mechanism.

Why did it come out this way? Numeric feedback ("+45,000" vs "−12,000") is visually higher-contrast for an LLM's attention mechanism than a verbal "correct/incorrect." After a few losses on weak Baseline models, the Predictor quickly recalibrates: it starts betting pennies on Gemma 2B and Haiku (which often get things wrong) and whale bets on Gemini/Sonnet (which are almost always right). In the control group this pattern shows up too, but more slowly — there's no vivid numeric anchor for "how bad was that."

A fun detail: in one run Qwen bet the minimum of 1 coin on all 25 first-round problems, then opened up sharply in round 2 — it looks like a "scout the risks first, then go aggressive" strategy. Grok and Mistral behaved more evenly. This shows that different models interpret the game framing in their own way.

09

Original from the Study

Context: The researcher used the following prompt for the Incentive group (with the betting mechanism). Below is a verbatim excerpt of the instruction in English, as it was given to the Predictor models:

You are an expert forecaster with a bankroll of 1,000,000 LLMCoin.

Your task: For each (question, baseline model) pair, predict whether the baseline 
model will answer the question correctly.

Rules:
- For each pair, output:
  • "predicted_correct": "Yes" or "No"
  • "stake": an integer between 1 and 100,000 LLMCoin
  • "rationale": brief explanation (~20 words max)

- If your prediction is correct, you WIN the stake (added to bankroll).
- If your prediction is incorrect, you LOSE the stake (subtracted from bankroll).

Constraints:
- The sum of stakes in a round must not exceed your current bankroll.
- If your bankroll drops below 1 coin, you go bankrupt and the game ends.

Goal: Maximize your final LLMCoin balance.

After each round, you will receive:
1. Correctness summary (which baselines answered which questions correctly)
2. Updated bankroll statement (wins, losses, new balance)

Output format (JSON-like):
{
  "round": [round number],
  "question_id": [id],
  "base_model_id": [id],
  "predicted_correct": "Yes" / "No",
  "stake": [integer 1-100000],
  "rationale": "[brief reasoning]"
}

For the control group the instruction was identical, but without the "stake" field and without any mention of a bankroll/bets. The goal was phrased as "Focus on being accurate" rather than "Maximize your bankroll."

10

Adaptations and Extrapolations

💡 Adaptation for work scenarios: rating your own ideas

The classic example from the study is predicting whether other models' answers are correct. But you can apply the same mechanics to rate your own options in any multiple-choice task.

Scenario: You have 15 headline variants for a landing page. You need to prioritize which ones to A/B test first.

Prompt:

You are a marketing analyst with a bankroll of 500,000 MarketCoin.

Task: for each headline, predict whether it will get a CTR above 8% 
on Google Ads traffic (B2B SaaS, audience: heads of sales).

Rules:
- For each headline, give a prediction: YES (>8% CTR) or NO (≤8%)
- Attach a stake of 1 to 50,000 MarketCoin to the prediction
- If the prediction is right → you win the stake
- If it's wrong → you lose the stake
- Total stakes across all headlines ≤ 500,000
- Goal: maximize your final balance

Format:
{
  "headline": "[text]",
  "prediction": "YES/NO",
  "stake": [number],
  "rationale": "[why]"
}

Headlines:
1. "Grow sales 40% in one quarter"
2. "A CRM your team doesn't need training to use"
3. "How we helped 50+ companies automate their sales team"
[... the other 12 variants]

After the predictions, show the top 5 by stake size.

Result: The model will place whale bets (30k-50k) on headlines with clear triggers for decision-makers (concrete numbers, pain points, fast results). Small bets (1k-5k) go to abstract or creative phrasings. You get a ranked shortlist for testing, based on the model's confidence in each variant.


🔧 Technique: multi-round feedback to train the model on the fly

In the original study, after each round the model received feedback (correct answers + an updated balance), and that sped up learning fourfold. You can simulate this in your own tasks, even if you don't have an objective truth.

Prompt modification:

[Base prompt with the betting mechanism]

After you give your predictions, I'll give you PARTIAL feedback 
(e.g., results for 5 items out of 20).

Then you'll revisit your predictions for the remaining 15 items and may 
change your stakes based on the new information.

Goal: maximize your final balance after all rounds.

Effect: The model adapts after the first wave of feedback. For example, if you were rating 20 business ideas and gave the model feedback on 5 (which ones actually raised money), it will recalibrate its stakes on the remaining 15 — lowering bets on similar ideas that flopped and raising them on those that took off.

This turns the method into iterative calibration, where the model learns from your data within a single conversation.


💡 Extrapolation: confidence scoring without a verifiable truth

The original method needs feedback (right/wrong) to update the balance. But you can use just the betting mechanics to get a confidence score, even when there's no objective truth.

Scenario: You're writing a content plan for the month. 30 post ideas. You need to see where the model is confident and where it's just winging it.

Prompt:

You are a content strategist with a bankroll of 1,000,000 ContentCoin.

Task: for each post idea, predict whether the post will get >500 likes 
in a marketing newsletter on Substack (30k subscribers).

Rules:
- For each idea: a YES/NO prediction + a stake of 1 to 100,000 coins
- You will NOT get feedback (this is a hypothetical bet)
- But imagine you're maximizing your balance — bet more where you're confident

Format: [standard JSON]

30 post ideas:
[list]

Show the top 10 by stake size (highest confidence).

Result: Even without real feedback the model will distribute stakes according to its internal confidence. You'll get a ranked list of ideas — the top 10 with whale bets = "the model thinks these will definitely land," the bottom with penny bets = "uncertainty here." It's better than a plain "rate 1-10" because the limited bankroll forces the model to choose.

11

Resources

Going All-In on LLM Accuracy: Fake Prediction Markets, Real Confidence Signals
Michael Todasco, James Silberrad Center for Artificial Intelligence, San Diego State University
Preregistered at OSF: https://osf.io/dc24t/

Research digest

Key result

The problem: LLMs are terrible at showing confidence. Ask for "yes/no" and you get a mushy "most likely." Give a 1-10 scale and everything drifts to 7-8. The Prediction Markets method lets you extract the model's hidden confidence through a numeric signal — the size of the bet on each prediction. The trick: don't ask for a confidence percentage — make the model risk virtual money. Give it a bankroll of 1M coins and a stake range of 1-100k per prediction. The model can't bet the max on everything — it has to choose. Big bets of 40k+ turned out right 99% of the time, small ones <1k only 74%. Bet size = an indicator of real confidence.

Principle

Not "rate your confidence on a 1-10 scale" (everything gets 7-8, zero differentiation) → Create a game with a limited resource. The model gets: - A bankroll of 1,000,000 coins - A stake range: 1 to 100,000 per prediction - A rule: right prediction = +stake, wrong = −stake - A constraint: total stakes in a round ≤ current balance The model is forced to rank tasks by confidence — it can't give everyone 100k, the money runs out. Where it sees clear signs of correctness, it bets big. Where there's uncertainty, pennies. After each round the model sees its updated balance: "+45,000" or "−12,000." Numeric feedback instead of a verbal "wrong."

Why it works

LLMs are bad at verbal assessments ("probably," "most likely" are fuzzy words) and on abstract scales (1-10 with no context). But they work great with numeric constraints and optimization tasks. The financial framing "maximize your bankroll" turns the request into an optimization problem with a finite resource. The model doesn't just generate "yes" — it calculates risk: a big bet = a big cost of being wrong. The stake becomes a proxy for internal probability — if the model sees an easy task + strong signals, it bets big; if it has doubts, it saves its money. Bonus: numeric feedback speeds up learning 4×. Models in Incentive mode improved accuracy by 12 percentage points between round one and round four; the control group (no bets) by only 2.9. Seeing "+45,000" is brighter for the model's attention than the word "correct."

When to apply

For ranking many assessments or forecasts (10-100+ items) → specifically when you need prioritization by confidence, not just a list of pros and cons. Examples: - Rating 50 startup ideas — where to dig deeper? - Predicting whether 100 problem solutions are correct — which to check manually? - Sorting 30 copy variants — which to bet on? NOT suitable for: - Subjective assessments with no verifiable outcome (how creative is the text? — the model won't get "won/lost" feedback) - Single assessments (nothing to rank, calibration gives no advantage)

Mini recipe

1. Create the game: give the model a role (analyst, expert) + a starting bankroll (usually 1,000,000 virtual coins). Invent a currency name (VCCoin, AnalystToken) — it strengthens the game framing. 2. Set the betting rules: a range of 1 to 100,000 coins per prediction. Payout rule: right prediction → +stake to balance, wrong → −stake. Constraint: total stakes ≤ current balance. 3. Define the criterion: a binary prediction with a verifiable outcome (will work/won't work, correct/incorrect, will raise funding/won't). Avoid subjective criteria. 4. Output format: for each item the model must give `{"name": "...", "prediction": "YES/NO", "stake": number, "rationale": "1-2 sentences"}`. 5. Ask for a summary: have the model show the top 5 items with the biggest stakes (high confidence) and the top 5 with the smallest (low confidence). That's your ranked priority list. 6. Optional — multi-round mode: after the first round, give feedback (which predictions were right), update the balance, run a second round. Numeric feedback speeds up the model's learning.

Examples

[BAD]: `Rate 20 edtech startup ideas on a 1-10 scale for how likely they are to raise a seed round` (Result: everything gets 6-8, you won't see any differences) [GOOD]: `You are a venture analyst with a bankroll of 1,000,000 VCCoin. For each of the 20 ideas, give a prediction: will it raise a seed round of $2M+ (YES/NO) + a stake of 1 to 100,000 coins. Rules: right prediction = +stake, wrong = −stake. Total stakes ≤ balance. Goal: maximize your final bankroll. Format: {"idea": "...", "prediction": "YES/NO", "stake": number, "rationale": "..."}. After all predictions, show the top 5 with the biggest stakes and the top 5 with the smallest.` (Result: the model will bet 60k-100k on ideas with clear product-market fit and measurable ROI, and pennies — 100-500 — on highly uncertain ideas. You'll see a numerically ranked list showing where the model "went all in" and where it has doubts)

In plain words

In Plain Words: 2512.05998

In Plain Words

Going All-In onLLMAccuracy: Fake Prediction Markets, Real Confidence Signals

Models are pathologically incapable of admitting they don't know something. When you ask a model about the future or have it pick a strategy, it always answers with the same poker face, even if inside it's total mush. The problem is that standard answers like "I'm fairly sure" or "probably" are empty noise you can't measure. Prediction Market Prompting cracks this open: it makes the model not just produce text but literally put resources at risk, turning abstract confidence into hard numbers.

It's like a friend who always gives "hundred-percent" advice, but the moment you offer to bet a year's salary on it, he starts hedging and asking for details. That's the whole point: when virtual money is on the line, the model stops spouting nonsense and starts acting like a professional trader. It has to weigh its knowledge against the risk of losing its bankroll, which instantly highlights the areas where the model is actually out of its depth.

The mechanics are simple but strict: you give the model starting capital, say 1,000,000 LLMCoin, and make it bet on its own predictions. If it puts 100,000 on one option and just 500 on another — congrats, you've got a real confidence signal instead of a boilerplate brush-off. A correct prediction grows the bank; a wrong one burns the stake. In this "sandbox" the model calibrates its own answers, because a survival game works more precisely than any attempt to imitate human politeness.

It was tested on forecasts, but the principle is universal. You can stretch this scheme over business planning, risk assessment in code, or choosing a marketing strategy. Instead of asking "which landing page is better," you make the AI invest in the options. If the model is ready to sink half its budget into one idea and pennies into another, you've got a ready-made priority list backed by expected value, not just hallucinations of happily-ever-after.

Bottom line: stop taking the model at its word and start playing high-stakes poker with it. If you want to squeeze the truth out of AI, don't ask it to "think" — ask it to place a bet. That turns useless text into a measurable decision-making tool, where the bet size is the only honest indicator of whether the forecast is worth listening to at all. Whoever doesn't build these "prediction markets" into their prompts will keep getting a bland average of everything instead of hard data.

ArXiv ID: 2512.05998 | Generated: 2026-01-02 04:14 | Nova Research

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