Hallucination Taxonomy

Core Hallucination Types

ADD-PATH — Unsupported Pathology

Adds a pathology, diagnosis, or finding that is not supported by the evidence.

ADD-DEVICE — Unsupported Medical Device

Adds a medical device (tube, line, catheter, pacemaker, etc.) that is not present in the image.

NEG-FLIP — Negation Reversal

Changes a present finding to absent or an absent finding to present.

LAT-FLIP — Laterality Reversal

Reverses the left–right laterality of a finding (for example, right → left).

CONTRA — Internal Contradiction

Introduces mutually inconsistent statements within the causal explanation.

The types listed above summarize the core hallucination categories. The complete and current taxonomy, including additional error types and labeling rules, is maintained in the Hidden-RAD2 Task 2 GitHub repository (link). Participants must follow the taxonomy version specified in the corresponding dataset release and submission guidelines.