Introduction

The groundbreaking paper by Google Brain at NeurIPS 2022 introduced the world to Chain-of-Thought Prompting (CoT). That changed a lot in prompting. But it didn’t stop there; it kicked off a whole new area of study, giving birth to various "chain" spin-offs and related research.

Just to give you an impression of the impact: a search for the keyword “chain-of-thought” pulls up 461 papers on Semantic Scholar and 374 on Arxiv. That’s a lot of papers! But we're not here to give you an exhaustive list you can find on any research platform. We aim to explore the papers with new ideas that have sprung from the original CoT research, map its influence, and decode the novelty and foundational principles of the followers.

In chronological order, we unfold the Chain-of-thought Lineage, with the following terms to explain:

No more confusion around CoT. Please use this up-to-date "dictionary" as a reliable reference point for understanding the complexities of this evolving field.

Recapping the fundamentals

Before diving into the nuanced world of chain-of-thought prompting – a specialized form of basic prompting – it's essential to revisit the foundational terminology in the prompting ecosystem.

Zero-shot prompting

The term "zero-shot prompting" derives from the concept of zero-shot learning*.

When we apply this intuition to prompting, this means that our prompt doesn’t contain any additional information for the model and provide any examples. In other words, the model can only use the knowledge it acquired during its training to produce the output.

In this brief example, the language model identifies the name "Steve Jobs" based on the prompt, without requiring any previous examples for named entity recognition. This effectively demonstrates the power of zero-shot prompting in action.

Zero-shot prompting contributes to the widespread adoption of LLMs. But sometimes it’s just not enough for a desired outcome. Adding a few examples for the model can help improve its output. And this is what we call few-shot prompting.

Few-shot prompting

Similar to its zero-shot counterpart, few-shot prompting also finds its roots in a similarly named learning approach: few-shot learning*.

Few-shot prompting can be used as a technique to enable in-context learning* where we provide demonstrations in the prompt to steer the model to better performance. The demonstrations serve as conditioning for subsequent examples where we would like the model to generate a response.

In this example, the first two statements serve as demonstrations to guide the model's behavior. The model then classifies the third statement as "Positive," using the preceding examples for contextual understanding.

Having established these foundational techniques, we now arrive at the intriguing world of chain-of-thought prompting. Let's talk about it.

Chain-of-thought prompting

For tasks demanding intricate reasoning and sequential thinking, merely providing a few examples proves to be insufficient. To address this, researchers suggested to use of a new technique called chain-of-thought prompting.

This new technique consists of modifying the original few-shot prompting by adding examples of problems and their solutions and a detailed description of intermediate reasoning steps while describing the solution. Consider this example from the original paper:

The authors of this approach showed how complex reasoning abilities emerge naturally in sufficiently large LMs via a chain-of-thought prompting. A series of intermediate reasoning steps for a given task significantly improves the ability of LLMs to perform complex reasoning.

Crucially, chain-of-thought prompting is an emergent ability tied to model scale, as identified by the authors in the paper “Emergent Abilities of Large Language Models.” Chain-of-thought prompting does not positively impact performance for small models and only yields performance gains when used with models of ∼100B parameters.

Chain-of-thought Lineage

While various prompting techniques exist, this review focuses on those intimately connected with chain-of-thought prompting. To ensure coherence, we'll proceed in chronological order to trace the evolution of ideas.

March 2022: Self-consistency

May 2022: Zero-Shot Chain-of-Thought (almost poetry here!) or just Zero-shot-CoT → ‘Let’s think step by step’ approach

October 2022: Automatic Chain of Thought (Auto-CoT) →

November 2022: Program-of-Thoughts Prompting (PoT) →

February 2023: Multimodal Chain-of-Thought Reasoning →

May 2023: Tree of Thoughts (ToT) →

August 2023: Graph of thoughts (GoT) →

September 2023: Algorithm-of-Thoughts (AoT) →

October 2023: Skeleton-of-Thought (SoT) →

Conclusion

The Chain-of-Thought paper kicked off a flurry of new prompting methods, each aiming to better mirror how people think. From Self-Consistency to Skeleton-of-Thought, these techniques aren't just incremental improvements; they're part of a bigger push to make machine reasoning more like human thought. We are anticipating further development in this field and will keep you posted about it.

While we've dug deep into the ideas behind the Chain-of-Thought paper, know that the word "chain" isn't just stuck there. There are new ideas and methods (such as chain-of-verification (CoVe), chain-of-density (CoD), etc.) that also use the term "chain," but take it in different directions. We'll break down these other "chain" ideas in our next tokens. Stay tuned!

Chain-of-Thought Applications

We've compiled a list of research papers that detail the application of the 'Chain-of-Thought' methodology as a foundational baseline across various domains.

Thank you for reading. You can leave your feedback in the comment section.