Past-State Contamination¶
Core Idea¶
Past-state contamination occurs when information that became available later enters a reconstruction, estimate, decision, or evaluation presented as valid for an earlier time. The result silently erases the boundary between what was knowable then and what is known now. A target time, an information set valid at that time, a later information item, a reconstruction or model claiming historical validity, and an illicit backward inclusion are required. The defect concerns availability timing, not whether the later information is true.
Broad Use¶
Backtests, historical databases, clinical chart review, incident investigation, archival reconstruction, and machine-learning validation preserve the target-time–information-cutoff relation.
Clarity¶
Hindsight bias is a psychological sense that an outcome was predictable. Look-ahead bias is the quantitative testing subtype. Data leakage can cross many boundaries other than time. Retrospective explanation may legitimately use later evidence if it does not claim contemporaneous knowability.
Manages Complexity¶
The abstraction turns scattered cases into one role-based test: identify the required elements, test their relation, and reject the classification when a constitutive commitment is missing.
Abstract Reasoning¶
Use the structural signature rather than the label, then challenge the nearest counterexample. Updating a historical account with newly discovered evidence is not contamination when the account explicitly speaks from the later vantage point.
Knowledge Transfer¶
Backtests, historical databases, clinical chart review, incident investigation, archival reconstruction, and machine-learning validation preserve the target-time–information-cutoff relation.
Example¶
A case qualifies only when the definition and every load-bearing role remain present. Updating a historical account with newly discovered evidence is not contamination when the account explicitly speaks from the later vantage point.
Relationships to Other Abstractions¶
Current abstraction Past-State Contamination Prime
Parents (1) — more general patterns this builds on
-
Past-State Contamination is a decomposition of Temporal Dynamics Prime
Removing domain vocabulary leaves an ordered availability relation in which later evidence crosses into an artifact asserted to represent an earlier state.
Children (2) — more specific cases that build on this
-
Hindsight Bias Domain-specific is a kind of Past-State Contamination
Hindsight Bias is the human-memory species in which outcome knowledge contaminates reconstruction of what was known or foreseeable before the outcome.
-
Data Leakage Prime is a kind of, conditional Past-State Contamination
Time leakage is the model-evaluation species in which future or held-out information enters fitting, feature construction, calibration, or validation.
Hierarchy path (1) — routes to 1 parentless root
- Past-State Contamination → Temporal Dynamics → Time
Not to Be Confused With¶
Hindsight bias is a psychological sense that an outcome was predictable. Look-ahead bias is the quantitative testing subtype. Data leakage can cross many boundaries other than time. Retrospective explanation may legitimately use later evidence if it does not claim contemporaneous knowability.
Notes¶
(Canonical first draft; queued for Claude house-style re-authoring and citation review.)