Quantifying Adaptability in Pre-trained Language Models with 500 Tasks

TL;DR

This paper introduces TaskBench500, a comprehensive benchmark to empirically analyze the adaptability of pre-trained language models across 500 diverse tasks, revealing key factors influencing their performance and limitations.

Contribution

The paper presents a large-scale empirical study using a new benchmark, TaskBench500, to systematically evaluate and understand the factors affecting language model adaptability to new tasks.

Findings

Adaptation procedures vary greatly in memorization ability.

Some tasks show compositional adaptability among models.

Mismatch in label distribution difficulty explains adaptation failures.

Abstract

When a neural language model (LM) is adapted to perform a new task, what aspects of the task predict the eventual performance of the model? In NLP, systematic features of LM generalization to individual examples are well characterized, but systematic aspects of LM adaptability to new tasks are not nearly as well understood. We present a large-scale empirical study of the features and limits of LM adaptability using a new benchmark, TaskBench500, built from 500 procedurally generated sequence modeling tasks. These tasks combine core aspects of language processing, including lexical semantics, sequence processing, memorization, logical reasoning, and world knowledge. Using TaskBench500, we evaluate three facets of adaptability, finding that: (1) adaptation procedures differ dramatically in their ability to memorize small datasets; (2) within a subset of task types, adaptation procedures exhibit compositional adaptability to complex tasks; and (3) failure to match training label distributions is explained by mismatches in the intrinsic difficulty of predicting individual labels. Our experiments show that adaptability to new tasks, like generalization to new examples, can be systematically described and understood, and we conclude with a discussion of additional aspects of adaptability that could be studied using the new benchmark.