SourceLanguage Model Cascades: Token-Level Uncertainty And Beyond
The paper computes the Pearson correlation between BLEURT scores and prediction lengths for FLAN-T5 models of five sizes (small, base, large, xl, xxl) on three WMT translation directions. All correlations are negative, ranging from -0.10 to -0.58, indicating that longer outputs are systematically lower quality. The strongest negative correlation is for the base model on WMT en→fr (-0.58), while the weakest is for the xxl model on WMT fr→en (-0.10). This confirms that output length carries some signal about quality, but the magnitude varies by model size and direction.