2019

Open Sesame: Getting Inside BERT's Linguistic Knowledge

Lin, Yongjie, Tan, Yi Chern, Frank, Robert

Understand

How and to what extent does BERT encode syntactically-sensitive hierarchical information or positionally-sensitive linear information? Recent work has shown that contextual representations like BERT perform well on tasks that require sensitivity to linguistic structure.

  • We present here two studies which aim to provide a better understanding of the nature of BERT's representations.
  • The first of these focuses on the identification of structurally-defined elements using diagnostic classifiers, while the second explores BERT's representation of subject-verb agreement and anaphor-antecedent dependencies through a quantitative assessment of self-attention vectors.
  • In both cases, we find that BERT encodes positional information about word tokens well on its lower layers, but switches to a hierarchically-oriented encoding on higher layers.

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