Lower Bounds on the Expressivity of Recurrent Neural Language Models

Fuente: arXiv
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Main Authors: Svete, Anej, Nowak, Franz, Sahabdeen, Anisha Mohamed, Cotterell, Ryan
Format: Preprint
Published: 2024
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author Svete, Anej
Nowak, Franz
Sahabdeen, Anisha Mohamed
Cotterell, Ryan
author_facet Svete, Anej
Nowak, Franz
Sahabdeen, Anisha Mohamed
Cotterell, Ryan
contents The recent successes and spread of large neural language models (LMs) call for a thorough understanding of their computational ability. Describing their computational abilities through LMs' \emph{representational capacity} is a lively area of research. However, investigation into the representational capacity of neural LMs has predominantly focused on their ability to \emph{recognize} formal languages. For example, recurrent neural networks (RNNs) with Heaviside activations are tightly linked to regular languages, i.e., languages defined by finite-state automata (FSAs). Such results, however, fall short of describing the capabilities of RNN \emph{language models} (LMs), which are definitionally \emph{distributions} over strings. We take a fresh look at the representational capacity of RNN LMs by connecting them to \emph{probabilistic} FSAs and demonstrate that RNN LMs with linearly bounded precision can express arbitrary regular LMs.
format Preprint
id arxiv_https___arxiv_org_abs_2405_19222
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Lower Bounds on the Expressivity of Recurrent Neural Language Models
Svete, Anej
Nowak, Franz
Sahabdeen, Anisha Mohamed
Cotterell, Ryan
Computation and Language
The recent successes and spread of large neural language models (LMs) call for a thorough understanding of their computational ability. Describing their computational abilities through LMs' \emph{representational capacity} is a lively area of research. However, investigation into the representational capacity of neural LMs has predominantly focused on their ability to \emph{recognize} formal languages. For example, recurrent neural networks (RNNs) with Heaviside activations are tightly linked to regular languages, i.e., languages defined by finite-state automata (FSAs). Such results, however, fall short of describing the capabilities of RNN \emph{language models} (LMs), which are definitionally \emph{distributions} over strings. We take a fresh look at the representational capacity of RNN LMs by connecting them to \emph{probabilistic} FSAs and demonstrate that RNN LMs with linearly bounded precision can express arbitrary regular LMs.
title Lower Bounds on the Expressivity of Recurrent Neural Language Models
topic Computation and Language
url https://arxiv.org/abs/2405.19222