What Do Recurrent Neural Network Grammars Learn About Syntax?
Paper · 2016 · Adhiguna Kuncoro, Miguel Ballesteros, Lingpeng Kong et al.
Summary
Neural parsers perform well, but it is hard to tell what syntactic knowledge they actually acquire. This paper treats recurrent neural network grammars (RNNGs) as objects of linguistic inquiry. RNNGs are generative models that build phrase-structure trees top-down using a stack, a buffer and an action history. On the English PTB (§02–21 train, §24 dev, §23 test), the authors train variants with components removed. They evaluate these on constituency parsing, on dependency parsing after conversion to Stanford dependencies, and on language modeling. They then add a gated attention mechanism to the composition function (GA-RNNG) to reveal which children a phrase vector depends on. A label-free version (U-GA-RNNG) tests how much nonterminal categories matter. Three findings emerge:
- Explicit composition on the stack is the decisive ingredient.
- Attention largely recovers lexical heads, mostly agreeing with hand-written head rules but sometimes spreading weight over several children, e.g. in conjunctions.
- Phrase vectors learned without labels still cluster into traditional categories.
These results support the endocentricity hypothesis and suggest that bracketing carries most of the syntactic information.
Key points
- Removing the stack hurts most: PTB §23 F1 falls from 93.3 (baseline RNNG) to 92.5. Dropping the buffer or the action history barely matters.
- A stack-only RNNG without ensembling reached 93.6 F1 on PTB. After conversion, it achieved 95.8 UAS and 94.6 LAS on PTB SD, the best supervised results reported at the time. GA-RNNG scored 93.5 F1.
- RNNGs beat linearized-tree models: 91.2 vs. 88.3 F1 against Vinyals et al. (2015) in the discriminative setting, and 93.3 vs. 92.6 against Choe and Charniak (2016) in the generative setting.
- In U-GA-RNNG, PP and SBAR phrases opening with preposition-like words cluster together. Phrases built on of and because form their own groups.
- Code and pretrained models are released at github.com/clab/rnng (interpreting-rnng).
Institutions
Fields, topics and concepts
📚 Shelves 6The field of science this work belongs to (OpenAlex fields).Computer Science · 18,614 worksArtificial Intelligence · 17,965 worksArts and Humanities · 17,450 worksLanguage and Linguistics · 17,296 worksNeuroscience · 186 worksCognitive Neuroscience · 185 works
🧭 Topics 1Research subjects and languages the work is about.Syntax & grammar formalisms · 221 works
Cite
Cite as Adhiguna Kuncoro, Miguel Ballesteros, Lingpeng Kong, Chris Dyer, Graham Neubig and Noah A. Smith. 2016. What Do Recurrent Neural Network Grammars Learn About Syntax?. arXiv:1611.05774.
@misc{kuncoro2016what,
title = {{What Do Recurrent Neural Network Grammars Learn About Syntax?}},
author = {Adhiguna Kuncoro, Miguel Ballesteros, Lingpeng Kong, Chris Dyer, Graham Neubig and Noah A. Smith},
year = {2016},
doi = {10.48550/arxiv.1611.05774},
eprint = {1611.05774},
archivePrefix = {arXiv},
url = {https://doi.org/10.48550/arxiv.1611.05774}
}References
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