hRoPE study shows compression depth, not location, signals real paragraph structure

Shuyang Xiang · hf · 2026-09-28

Standard positional encodings represent position as a 1D reading-order coordinate, missing hierarchical structure. This work proposes hierarchical RoPE (hRoPE) with separate channels for paragraph, sentence, and token indices.

Holding the token sequence fixed and intervening on the paragraph coordinate p1, the authors measure cross-paragraph attention with a token-distance-exact estimator. Attention compresses relative to a matched baseline—but compression alone isn't diagnostic: an identical channel with density-matched random labels also compresses, just more shallowly.

The reproducible signature of genuine structure is compression depth: deeper and corpus-dependent for real paragraph structure, absent in controls. Of eight corpus-only quantities tested (lexical persistence, paragraph length, embedding-based coherence), none fully reproduces the cross-corpus ordering of depth, though embedding-based coherence comes closest.

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