Steering Llama 2 via Contrastive Activation Addition
Authors: Nina Panickssery, Nick Gabrieli, Julian Schulz, Meg Tong, Evan Hubinger, Alexander Matt Turner
AI-generated Key Points
- Researchers Nina Panickssery, Nick Gabrieli, Julian Schulz, Meg Tong, Evan Hubinger, and Alexander Matt Turner introduce Contrastive Activation Addition (CAA) for guiding language models.
- CAA involves adjusting activations during forward passes by computing "steering vectors" comparing residual stream activations between positive and negative examples of specific behaviors.
- Steering vectors are added to user prompts with positive or negative coefficients to control desired behavior.
- CAA significantly influences model behavior while minimally impacting overall capabilities when evaluated on Llama 2 Chat with various behavioral question datasets and open-ended generation tasks.
- Insights into CAA's mechanisms are gained through different activation space interpretation methods.
- The research demonstrates how CAA accurately guides model outputs and provides insights into the representation of high-level concepts in Large Language Models (LLMs).
- An example illustrating the impact of sycophancy steering using CAA on open-ended generation tasks with Llama 2 7B at layer 13 using specific multipliers is provided in Table 1.
- Diagrams illustrate the process of generating steering vectors for CAA and applying them during inference to effectively control model behavior.
- Overall, this research highlights Contrastive Activation Addition as an innovative approach to steer language models towards desired behaviors and its significance in understanding Large Language Models.
Abstract: We introduce Contrastive Activation Addition (CAA), an innovative method for steering language models by modifying their activations during forward passes. CAA computes "steering vectors" by averaging the difference in residual stream activations between pairs of positive and negative examples of a particular behavior, such as factual versus hallucinatory responses. During inference, these steering vectors are added at all token positions after the user's prompt with either a positive or negative coefficient, allowing precise control over the degree of the targeted behavior. We evaluate CAA's effectiveness on Llama 2 Chat using multiple-choice behavioral question datasets and open-ended generation tasks. We demonstrate that CAA significantly alters model behavior, is effective over and on top of traditional methods like finetuning and system prompt design, and minimally reduces capabilities. Moreover, we gain deeper insights into CAA's mechanisms by employing various activation space interpretation methods. CAA accurately steers model outputs and sheds light on how high-level concepts are represented in Large Language Models (LLMs).
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