# Hallucinations in LLMs



## How Hallucination is Addressed in LLMs Using Chain-Of-Verification (CoVe)?

### What is hallucination in an LLM model?

One significant issue with LLMs is their tendency to produce "hallucinations," which affect their reliability. Hallucinations in LLMs refer to the generation of content that is irrelevant, made-up, or inconsistent with the input data. This problem leads to incorrect information, challenging the trust placed in these models.

### The paper addresses the problem of hallucinations in LLMs by introducing the Chain-of-Verification (CoVe) method, by following these 4 steps process:

1. Generate Baseline Response: Given a query, generate the initial response using the LLM.
2. Plan Verifications: Given both query and baseline response, generate a list of verification questions that could help to self-analyze if there are any mistakes in the original response.
3. Execute Verifications: Answer each verification question in turn, and hence check the answer against the original response to check for inconsistencies or mistakes.
4. Generate Final Verified Response: Given the discovered inconsistencies (if any), generate a revised response incorporating the verification results.

The process ensures independent verification to avoid biases and repeated mistakes.

It requires the use of a single LLM, without the multi-agent (multi-LLM) debate concept. No finetuning or pre-training needed.

### The authors investigated further (4) approaches for the step n°3:

1-Joint: Step 2 and 3 are performed using a single prompt, using few-shot examples where both verifications questions and their answers are included immediately after the questions.

2- Two-step: Separates planning and execution, both with their own prompt:

* Step 1: Verification questions are generated based on the initial response.
* Step 2: These questions are answered without referencing the original response, it contains only the question ⇒ reducing the risk of repeating mistakes.

4- Factored: Answer all verification questions independently as separate prompts that don’t reference the original response.

5- Factor + revise: Additional step after answering verification questions. Explicitly checks for inconsistencies between the original response and the verification answers. Each verification question and answer is cross-checked against the original response using separate prompts, which helps the system identify and reason about any inconsistencies.

Factored and factor+revise approaches showed the best performance, particularly in reducing repeated hallucinations.

### Various tasks evaluated:&#x20;

1- List-based questions (Wikidata, Wikipedia Category list) “Who are some politicians who were born in Boston?”

2- Closed book QA (MultiSpanQA) “Q: Who invented the first printing press and in what year?, A: Johannes Gutenberg, 1450.”

3- Longform text generation of biographies

Different LLMs have been evaluated (depending on the task): LLama 65B, Llama 2 70B Chat, ChatGPT, InstructGPT, PerplexityAI. Alongside different prompt techniques: Zero-Shot CoT, CoT, Few-shot, CoVe and its verification execution variants.

**Results:** The method consistently reduced hallucinations and improved accuracy across all tasks compared to baseline models.

**Paper:** [Chain-of-Verification Reduces Hallucination in Large Language Models **arxiv 2309.11495**](https://arxiv.org/abs/2309.11495)

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