Causal Role of Lexical Departure in Verification Failure

Determine whether lexical departure from cited video transcript content causally leads to verification failure (unsupported claims) in video-grounded outputs generated by the Gemini 2.5 Pro multimodal generative search system, or whether the observed association between lexical departure and verification failure is non-causal and merely co-occurs with such failures.

Background

The audit finds strong associations between unsupported claims and two features: reduced verbatim noun overlap with source text and lower semantic similarity to transcripts. While these features are consistently protective when present, the analysis is explicitly correlational and does not establish causation.

The authors note that this observed relationship may result from a shared underlying factor (e.g., parametric knowledge injection or paraphrasing) rather than a direct causal effect of lexical departure, motivating the need to establish whether lexical divergence itself drives verification failure.