Simple Next-Token Predictors are Powerful Universal Learners, Challenging Complexity Assumptions of Large Language Models

This is a Plain English Papers summary of a research paper called Simple Next-Token Predictors are Powerful Universal Learners, Challenging Complexity Assumptions of Large Language Models. If you like these kinds of analysis, you should join AImodels.fyi or follow me on Twitter.

Overview

• This paper explores the surprising capabilities of simple next-token prediction models in logical and mathematical reasoning tasks.
• The authors present a theoretical framework to study auto-regressive next-token predictors, demonstrating that even linear models trained on Chain-of-Thought (CoT) data can efficiently approximate functions computed by Turing machines.
• The paper introduces a new complexity measure, "length complexity," and analyzes its relationship with other notions of complexity.
• Experiments show that simple next-token predictors, such as linear networks and shallow Multi-Layer Perceptrons (MLPs), can perform non-trivial text generation and arithmetic tasks.
• The results suggest that the power of large language models (LLMs) can be largely attributed to the auto-regressive next-token training scheme, rather than a specific architectural choice.

Plain English Explanation

The paper explores how even simple machine learning models trained to predict the next word in a sequence can develop surprisingly powerful reasoning abilities. The authors show that these basic "next-token prediction" models can effectively approximate the behavior of complex computational systems, like Turing machines, when trained on a special type of data called "Chain-of-Thought" (CoT).

The key insight is that the process of predicting the next word in a sequence forces the model to learn to break down complex tasks into a series of small, manageable steps. This "chain of thought" allows the model to tackle problems that would otherwise be too difficult for its simple architecture.

The paper introduces a new way to measure the complexity of these CoT sequences, called "length complexity," which looks at how many intermediate steps are required to solve a given problem. The authors find that there is an interesting relationship between this length complexity and other notions of complexity, such as the difficulty of the underlying task.

Importantly, the researchers show that even very simple models, like linear networks and shallow neural networks, can perform surprisingly well on tasks like text generation and arithmetic when trained in this way. This suggests that the impressive abilities of today's large language models are not due to their complex architectures, but rather to the power of the auto-regressive next-token training approach.

Technical Explanation

The paper presents a theoretical framework for studying auto-regressive next-token predictors, which are the core components of modern large language models (LLMs). The authors demonstrate that even simple models, such as linear next-token predictors, can approximate any function efficiently computed by a Turing machine when trained on Chain-of-Thought (CoT) data.

The key contribution is the introduction of a new complexity measure, called "length complexity," which quantifies the number of intermediate tokens in a CoT sequence required to approximate a target function. The authors analyze the relationship between length complexity and other notions of complexity, such as Kolmogorov complexity and computational complexity.

The paper also presents experimental results showing that simple next-token predictors, including linear networks and shallow Multi-Layer Perceptrons (MLPs), can display non-trivial performance on text generation and arithmetic tasks. These findings suggest that the remarkable capabilities of today's LLMs can be largely attributed to the auto-regressive next-token training scheme, rather than a specific architectural choice, as explored in related work and further research.

Critical Analysis

The paper provides a compelling theoretical framework for understanding the power of auto-regressive next-token prediction models, but there are a few caveats to consider:

1. The analysis is largely focused on linear and shallow models, which may not fully capture the complexity of modern LLMs that often employ deep, multi-layer architectures. Further research is needed to understand how the insights from this paper scale to more advanced models.

2. The experiments are limited in scope, focusing on relatively simple text generation and arithmetic tasks. It would be valuable to explore the model's performance on a wider range of complex, real-world problems to fully assess the generalization of the findings.

3. The paper does not address potential issues with next-token prediction models, such as their tendency to generate repetitive or incoherent text, as discussed in related research. Addressing these challenges will be crucial for building robust and reliable language models.

Overall, this paper provides a thought-provoking theoretical framework and experimental insights that challenge the common assumption that the architectural complexity of LLMs is the primary driver of their capabilities. The findings suggest that the auto-regressive training approach may be a more fundamental source of their power, opening up new avenues for research and development in this field.

Conclusion

This paper presents a novel theoretical framework for understanding the remarkable capabilities of auto-regressive next-token prediction models, even in complex logical and mathematical reasoning tasks. The authors introduce a new complexity measure, "length complexity," and demonstrate that simple linear and shallow models can effectively approximate functions computed by Turing machines when trained on Chain-of-Thought data.

The experimental results further show that these basic next-token predictors can perform non-trivial text generation and arithmetic tasks, suggesting that the power of today's large language models may be more closely tied to the auto-regressive training scheme than to their architectural complexity. These findings challenge the prevailing assumptions in the field and open up new directions for research and development in language modeling and related areas of artificial intelligence.

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