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Markets / Neuroscience / Human neurogenesis

New adult brain neurons exceed the stated annual rate.

Do new neurons that survive a year add more than 0.1% to the specified adult brain-cell population? The rule fixes which cells, ages and reference population count.

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This week's round did not come back live. The number below is the last live round — round 1, published Oct 19, 2026 07:03 PM EDT — not this week's reading.

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Each dot is one recorded reading, thinned to hourly for readability; the underlying samples are every few minutes. The line between two dots is not a measurement. How the AI estimate is made.

Weekly AI estimate

44% Last live round · Oct 19, 2026 07:03 PM EDT

The average of three models reading the same evidence. It is an estimate, not proof the hypothesis holds, and it does not set the pool price.

Last live round
Oct 19, 2026 07:03 PM EDT

The live panel was called but did not return three estimates · so this round did not return all three estimates and the number is a labelled stand-in

Market definition · YES, NO and evidence rules

This is the frozen contract wording. Read the YES and NO tests, the evidence requirements and the undecided cases before taking a position.

Canonical title

Standardized adult dentate-neuron surviving additions exceed 0.1% in one year.

Exact hypothesis · technical wording

In adults without diagnosed neurological disease, the age-standardized mean one-year surviving addition fraction of dentate-gyrus granule neurons exceeds 0.001. At exact age a, define r(a)=N_new(a,a+1)/N_total(a): N_new counts cells whose final mitosis occurs during [a,a+1) Julian years of age and which are alive and differentiated as mature dentate granule neurons at a+1; N_total counts ALL mature dentate granule neurons in both hippocampi at a, including nonrenewing neurons. Births that die before the endpoint, progenitor proliferation, DNA repair and prenatal cells maturing late do not enter the numerator. The target is the arithmetic mean of r(a), not a median or a renewing-subpopulation turnover rate, standardized uniformly over 25 <= a < 65 and equally across female and male biological-sex strata. Within each age/sex stratum, the reference population is neurologically healthy US residents with the remaining demographic distribution of the 2020 US census. This reference distribution, age range, one-year endpoint and threshold are contract conventions, not a universal human rate.

Each round reads the evidence that was public at a stated cutoff. Later evidence goes into a later round; the market itself has no expiry date.

How the evidence cutoff is fixed

A round only counts evidence published before its own cutoff time, and the round's number is that timestamp. So a round cannot borrow a later cutoff, and an earlier round's judgment cannot be reused for a later one. The hypothesis wording, the resolution criteria and the methodology identifier were hashed into the market account at creation, which is what stops any of them being edited afterwards.

Resolution criteria

YES: Each independent birth-dating or validated-lineage study estimates this same standardized mean and places its 95% interval wholly above 0.001, with mature granule-neuron identity, survival to the one-year endpoint, the all-neuron denominator and age/sex/demographic standardization identified. Require >= 20 independent donors with age coverage throughout the domain, controls for DNA repair/contamination/tissue processing, and uncertainty propagated from birth-death and population-transport models. Cross-sectional carbon dating is eligible only if the specified one-year surviving-addition estimand is identifiable and robust to supported birth-death models. NO: Each otherwise eligible independent study places the 95% upper bound for that same standardized mean <= 0.001. Unidentified one-year survival, unsupported transport to the reference population, an interval crossing 0.001, immature-neuron markers alone, or a rate within only a renewing subpopulation leaves this contract UNDECIDED. Reference sources: Spalding et al.: dynamics of hippocampal neurogenesis (https://doi.org/10.1016/j.cell.2013.05.002); 2020 US census reference population (https://www.census.gov/programs-surveys/decennial-census/decade/2020.html); Adult human proliferating neural progenitors (https://www.science.org/doi/10.1126/science.adu9575); Human hippocampal neurogenesis in ageing (https://www.nature.com/articles/s41586-026-10169-4). Evidence policy: use public primary research with methods and uncertainty, plus the named reference sources below. A preprint can inform the estimate but cannot alone meet a terminal criterion; require a peer-reviewed primary result and an independent reproduction using non-overlapping observations or independently prepared samples, unless this is a mathematical proof or the specific criterion instead requires independently implemented calculations. Report data provenance, exclusions, calibration, statistical model and systematic uncertainty. Independence means different data acquisition, not two papers reanalysing the same sample. For a quantitative terminal test, both independent results must meet the stated threshold; disagreement or an interval crossing the boundary means UNDECIDED. Use the final corrected version public at the signed round's evidence cutoff (UTC); exclude later evidence until a later eligible round. Every report in a terminal round must use the same cutoff, covered by the verified signed context and enforced by the configured terminal protocol; a different cutoff requires a new eligible round, never reinterpretation of a signed report or mutation of an immutable binding. This market has no calendar expiry. Retracted findings cannot supply a terminal result. If a named source disappears, use its DOI/publisher or an archived identical version, then an equivalent primary publication applying these unchanged definitions; if none is accessible, remain UNDECIDED, never substitute a different test. Missing data, failed replication, a null search outside the specified domain, or an untested alternative is not automatically NO. These are instructions for evidence assessment, not an automatic truth oracle: scientific interpretation and systematic-error judgment remain. Settlement follows the configured platform mode: terminal mode requires one valid round with all three frozen models returning the same explicit YES or NO and criterion_met=true; any UNDECIDED, failure or disagreement leaves it unresolved. Legacy proposal/challenge mode requires its recorded review process. Model agreement does not prove scientific truth. Invalidity is not NO and this text does not authorize a refund or cancellation: only a cancellation rule disclosed before exposure, if the configured contract supports it, can apply. Otherwise pause new entries and preserve holders' existing rights. Never reinterpret terms after listing.

The definition does not change when an AI estimate changes. Read the listing policy and this market's settlement status.

How each model argued

The live panel was called but did not return all three estimates. This round kept the previous estimate as a labelled placeholder, not an average of the answers that came back.

This round ran under methodology panel-v9. Short excerpts are below; the round 5 page keeps the full answers, sources and raw responses. The current methodology and example requests do not reconstruct this historical round's exact request.

OpenAI placeholder 0.41

local-fallback

The live panel was called for this round and did not return three usable answers, so this is a placeholder around the previous estimate rather than an average of model output. It is not an assessment.

Full explanation from OpenAI→
Anthropic placeholder 0.44

local-fallback

The live panel was called for this round and did not return three usable answers, so this is a placeholder around the previous estimate rather than an average of model output. It is not an assessment.

Full explanation from Anthropic→
xAI placeholder 0.47

local-fallback

The live panel was called for this round and did not return three usable answers, so this is a placeholder around the previous estimate rather than an average of model output. It is not an assessment.

Full explanation from xAI→

What moved the number

—
Oct 16

This is a new contract, not a migrated position or a continuation of old forecast history. The initial 0.50 is an initialization convention, not an AI forecast or an assessed scientific probability. Reference links are background sources,…

Nov 10
0.44 0.44 0.0 no model output

Live panel did not return all three estimates (xAI failed or gave an unusable answer). A round is only live when all three are valid, so this round is a placeholder at the previous score rather than an average of two.

This round's saved score, answers and sources →
Nov 9
0.44 0.44 0.0 no model output

Live panel did not return all three estimates (OpenAI, Anthropic, xAI failed or gave an unusable answer). A round is only live when all three are valid, so this round is a placeholder at the previous score rather than an average of two.

This round's saved score, answers and sources →
Oct 19

OpenAI estimated 0.65. Carbon dating supports appreciable adult neuronal addition, making the threshold plausible, but its model-dependent renewing-fraction turnover is not the specified standardized one-year surviving-addition fraction.…

This round's saved score, answers and sources →
—
Oct 19

AI estimate scheduled: an independent three-model panel reads the published definition and evidence every week. New positions are still closed for this market, so the estimate is here to read, not to trade against.

The evidence packet · 7 entries

What the panel was shown when this round ran. A row with no source link is a description only, and the panel is told so.

Spalding et al.: dynamics of hippocampal neurogenesis

Context

Carbon dating plus birth-death modelling estimates about 1.75% annual turnover WITHIN a renewing neuronal fraction, not 1.75% of all hippocampal neurons; it does not directly establish this standardized one-year surviving-addition target.

Source link

2020 US census reference population

Context

Reference for demographic standardization, not neurogenesis evidence.

Source link

Adult human proliferating neural progenitors

Context

Single-cell and proliferation evidence supports progenitors, not this exact population renewal rate.

Source link

Human hippocampal neurogenesis in ageing

Context

Multiomic study distinguishes progenitors and immature neurons; expression is not automatically cell birth dating.

Source link

Required positive observation

Supporting

Each independent birth-dating or validated-lineage study estimates this same standardized mean and places its 95% interval wholly above 0.001, with mature granule-neuron identity, survival to the one-year endpoint, the all-neuron denominator and age/sex/demographic standardization identified. Require >= 20 independent donors with age coverage throughout the domain, controls for DNA repair/contamination/tissue processing, and uncertainty propagated from birth-death and population-transport models. Cross-sectional carbon dating is eligible only if the specified one-year surviving-addition estimand is identifiable and robust to supported birth-death models.

Description only · no source link recorded

Required contrary observation

Contrary

Each otherwise eligible independent study places the 95% upper bound for that same standardized mean <= 0.001. Unidentified one-year survival, unsupported transport to the reference population, an interval crossing 0.001, immature-neuron markers alone, or a rate within only a renewing subpopulation leaves this contract UNDECIDED.

Description only · no source link recorded

Eligibility and unresolved outcomes

Method

Evidence policy: use public primary research with methods and uncertainty, plus the named reference sources below. A preprint can inform the estimate but cannot alone meet a terminal criterion; require a peer-reviewed primary result and an independent reproduction using non-overlapping observations or independently prepared samples, unless this is a mathematical proof or the specific criterion instead requires independently implemented calculations. Report data provenance, exclusions, calibration, statistical model and systematic uncertainty. Independence means different data acquisition, not two papers reanalysing the same sample. For a quantitative terminal test, both independent results must meet the stated threshold; disagreement or an interval crossing the boundary means UNDECIDED. Use the final corrected version public at the signed round's evidence cutoff (UTC); exclude later evidence until a later eligible round. Every report in a terminal round must use the same cutoff, covered by the verified signed context and enforced by the configured terminal protocol; a different cutoff requires a new eligible round, never reinterpretation of a signed report or mutation of an immutable binding. This market has no calendar expiry. Retracted findings cannot supply a terminal result. If a named source disappears, use its DOI/publisher or an archived identical version, then an equivalent primary publication applying these unchanged definitions; if none is accessible, remain UNDECIDED, never substitute a different test. Missing data, failed replication, a null search outside the specified domain, or an untested alternative is not automatically NO. These are instructions for evidence assessment, not an automatic truth oracle: scientific interpretation and systematic-error judgment remain. Settlement follows the configured platform mode: terminal mode requires one valid round with all three frozen models returning the same explicit YES or NO and criterion_met=true; any UNDECIDED, failure or disagreement leaves it unresolved. Legacy proposal/challenge mode requires its recorded review process. Model agreement does not prove scientific truth. Invalidity is not NO and this text does not authorize a refund or cancellation: only a cancellation rule disclosed before exposure, if the configured contract supports it, can apply. Otherwise pause new entries and preserve holders' existing rights. Never reinterpret terms after listing.

Description only · no source link recorded

Past estimates

Every weekly estimate, newest first
DateEstimateRange
Nov 10, 2026 09:31 PM EST 44% no live reading
Nov 09, 2026 09:20 AM EST 44% no live reading
Nov 02, 2026 09:20 AM EST 44% no live reading
Oct 26, 2026 10:20 AM EDT 44% no live reading
Oct 19, 2026 07:03 PM EDT 44% 30–65%

Discussion

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