What Makes Instruction Learning Hard? An Investigation and a New Challenge in a Synthetic Environment

TL;DR

This paper investigates the challenges of instruction learning in large transformer models using a synthetic environment focused on regular expression tasks, revealing difficulties with complex instructions and long context tracking.

Contribution

It introduces Hard RegSet, a new challenging dataset for instruction learning, and provides insights into the properties that make instruction learning difficult for models.

Findings

Models struggle with large regular languages and less precise instructions.

Longer context tracking increases difficulty in instruction execution.

Fine-tuned models achieve only 65.6% accuracy on Hard RegSet.

Abstract

The instruction learning paradigm -- where a model learns to perform new tasks from task descriptions alone -- has become popular in general-purpose model research. The capabilities of large transformer models as instruction learners, however, remain poorly understood. We use a controlled synthetic environment to characterize such capabilities. Specifically, we use the task of deciding whether a given string matches a regular expression (viewed as an instruction) to identify properties of tasks, instructions, and instances that make instruction learning challenging. For instance, we find that our model, a fine-tuned T5-based text2text transformer, struggles with large regular languages, suggesting that less precise instructions are challenging for models. Additionally, instruction executions that require tracking longer contexts of prior steps are also more difficult. We use our findings to systematically construct a challenging instruction learning dataset, which we call Hard RegSet. Fine-tuning on Hard RegSet, our large transformer learns to correctly interpret only 65.6% of test instructions (with at least 90% accuracy), and 11%-24% of the instructions in out-of-distribution generalization settings. We propose Hard RegSet as a challenging instruction learning task, and a controlled environment for studying instruction learning.