Splitting a bidirectional LSTM's contextual representation into a forward-only Fi (strictly a function of tokens 1..i) and a backward-only Bi (strictly a function of tokens i..n) beats either alone and beats a fused self-attention representation for dependency relation-type classification. But a specific, natural extension of this idea -- pairing a token's forward state against a candidate's backward state (``cross-direction'' pairing, Fi vs.\ Bj) -- consistently underperforms same-direction pairing, and the penalty grows, not shrinks, with token distance, both paired-bootstrap significant. We diagnose why using a frozen-trunk methodology: architectural information leakage between directions is impossible by construction (a single-layer BiLSTM, verified by code inspection); 93% of the same-vs-cross gap survives freezing the trunk and training only fresh heads, ruling out training-co-adaptation as the primary cause; linear regression shows partial representational redundancy between Fi and Bi (R2=0.324 vs.\ 0.028 for a shuffled control) and a linear probe shows partial anticipatory encoding of upcoming tokens in Fi (36.5% vs.\ 17.2% majority baseline) -- real effects, but neither alone, nor combined, cleanly explains the full gap. Extended frozen-trunk diagnostics (a positional probe and a distance-decay probe) show directional information is genuinely stored but not exactly positioned, and propagates only a few tokens before decaying to baseline -- consistent with, and mechanistically underneath, the distance-growth finding.
Figures & tables
Fig. 1: Trunk architecture. A single-layer BiLSTM over token embeddings exposes Fi and Bi directly, with no attention or mixing layer between the LSTM and the split. Pi is computed independently of the LSTM. Hi=concat(Fi,Bi,Pi) is the per-token diagnostic representation used by the positional and distance-decay probes (Section V C).
Variant
Test Acc.
5-seed Acc.
Macro-F1
Params
f_only
0.9667
0.9650 ± .0016
0.9654
1.39M
b_only
0.9625
0.9622 ± .0011
0.9617
1.39M
f_plus_b
0.9725
–
0.9720
1.52M
f_plus_b_plus_p
0.9733
0.9716 ± .0020
0.9732
1.54M
standard_attention
0.9652
0.9646 ± .0009
0.9645
2.34M
TABLE I: Relation-type classification, test set. Single-seed columns are the primary run; 5-seed column (mean ± std, seeds 42–46) confirms it.
Variant
Test Acc.
Test F1
Params
same_f (FF)
0.9362 ± 0.0004
0.9364 ± 0.0003
1.39M
same_b (BB)
0.9351 ± 0.0014
0.9354 ± 0.0015
1.39M
cross_fb (FB)
0.9050 ± 0.0018
0.9058 ± 0.0025
1.39M
cross_bf (BF)
0.8588 ± 0.0022
0.8582 ± 0.0025
1.39M
combined_e
0.9543 ± 0.0004
0.9547 ± 0.0004
1.40M
full_ref
0.9522 ± 0.0015
0.9524 ± 0.0016
1.54M
TABLE II: Binary edge existence, test set, mean ± std over 3 seeds.
∣i−j∣ bucket
1–2
3–5
6–10
11–20
21+
n (test pairs)
19,571
11,639
7,576
5,188
1,922
Accuracy gap
− 0.0233
− 0.0300
− 0.0384
− 0.0502
− 0.0538
F1 gap
− 0.0166
− 0.0324
− 0.0606
− 0.1045
− 0.1137
TABLE III: cross_fb − same_f accuracy/F1 gap by token distance (test, mean over 3 seeds).
Fig. 2: cross_fb − same_f accuracy and F1 gap by token-distance bucket (test set, mean over 3 seeds). Both gaps are monotonically negative and grow with distance – the opposite of the “masked by short-range dominance” prediction.
Condition
same_f Acc.
cross_fb Acc.
Frozen trunk (fresh heads, 3 seeds)
0.9240 ± 0.0008
0.8943 ± 0.0006
End-to-end
0.9367 ± 0.0001
0.9049 ± 0.0017
TABLE IV: Frozen-trunk vs. end-to-end same_f − cross_fb accuracy gap.
Source
Dim
MLP Acc.
Linear Acc.
MLP Frac. MAE
Fi
128
0.3310
0.3103
0.1920
Bi
128
0.3314
0.2983
0.1919
Fi+Bi (no P )
256
0.4830
0.4072
0.1436
Hi (with Pi )
320
0.6679
0.5140
0.1350
TABLE V: Position-probe bucket accuracy, MLP vs. linear head, mean over 3 seeds (majority baseline 0.1367). MAE columns are for the MLP head’s normalized-position regression (median baseline MAE 0.2718).
The reversal curse describes a failure of autoregressive language models to retrieve a fact in reverse order (e.g., training on $A > B$'' but failing on B<A''). Recent work shows that objectives with bidirectional supervision (e.g., bidirectional attention or masking-based reconstruction for decoder-only models) can mitigate the reversal curse. We extend this evaluation to include a vanilla masked language modeling (MLM) objective and compare it to decoder-only masking-based training across four reversal benchmarks and then provide a minimal mechanistic study of how these objectives succeed. We show that reversal accuracy requires training signal that explicitly makes the source entity a prediction target, and we find little evidence that success corresponds to a single direction-agnostic representation of a fact. Instead, representation distances and linear probes are consistent with storing forward and reverse directions as distinct entries, with different indexing geometry for MLM versus decoder-only masking-based training. Our results caution that objective-level ``fixes'' can improve reversal behavior without necessarily inducing the kind of latent generalization one might expect from a unified concept.
Extracted sentiment directions can vary across samples even when downstream sentiment classification remains accurate. To evaluate direction reproducibility, we measure split-half agreement in English, Hausa, and Yoruba representations across four language models using both native and translated texts. We identify layers selected for agreement using ten topics and evaluate direction agreement across separate groups of fifteen topics. Using the final token, split-half agreement ranges from 0.737 to 0.870 for English, 0.589 to 0.762 for Hausa, and 0.101 to 0.399 for Yoruba, maintaining this language rank order across all 77 complete model comparisons. Classifiers trained on these same layers consistently predict sentiment above chance, demonstrating that predictive accuracy does not imply directional consistency. Furthermore, averaging token representations yields less consistent agreement, and high agreement can partially reflect sentence length. Ultimately, our findings highlight the need to measure vector direction reproducibility independently of classification performance, though they do not establish that tokenizer fertility which is the average number of tokens per whitespace separated word causes cross-lingual differences.
Muhammad Abdullahi Said, Abass Oguntade, Elisha Komolafe +3
African Institute for Mathematical Sciences · University of Cape Town · Bayero University Kano +2
CLIP-like vision-language models remain a cornerstone of multimodal systems, yet their scores stay near chance on directed spatial relations, such as whether one object is left of another. We call this failure readout blindness and analyze, theoretically and empirically, why deployed scores miss the direction: when scoring rules treat the subject and object symmetrically, direction cancels regardless of encoder training. Guided by this analysis, we introduce Antisymmetric Displacement Readout (ADR), which aligns caption words with image patches in the frozen features and scores each relation by the signed displacement between matched object centroids. Notably, ADR succeeds without additional training or learned parameters, thereby demonstrating that directional information remains in the frozen encoder. However, text and world priors can inflate accuracy, so we further introduce prior deflation, which measures the benefit of the image-text pairing as the grounded gain over a null that pairs each item with an unrelated image. Extensive experiments across encoder families show that ADR substantially improves over deployed scores, which remain near chance on most direction-balanced sets even for fine-tuned encoders. Compared with more complex readouts, ADR outperforms the evaluated MLLM likelihood readouts and is competitive with their chat inference at a small fraction of the computation. These results support our claim that directional information can be recovered from frozen features by an appropriate readout. Our implementation and evaluation kit will be publicly available.
Guangyuan Li, Tianming Du, Yan Jiang +2
ELLIS Institute Finland · Aalto University · University of Oulu +1