Reinforcement learning (RL) is a subset of machine learning that involves an agent learning to interact with an environment to achieve a specific goal. In RL, the agent takes actions based on the current state of the environment and receives a reward or penalty for each action it takes. The goal of RL is for the agent to learn to take actions that maximise its long-term reward.

While RL can be effective at learning to make decisions in a wide range of environments, there are many situations where it is difficult or impossible to define a reward function that accurately captures the desired behaviour. In these cases, it may be possible to provide feedback to the agent in the form of human guidance. This approach, known as reinforcement learning with human feedback (RLHF), has the potential to make RL applicable in a wide range of settings.

https://www.deepmind.com/blog/learning-through-human-feedback

In this blog post, we will explore how RLHF works, including the different types of human feedback, the challenges involved in designing RLHF systems, and the current state-of-the-art in RLHF research.

Types of Human Feedback

There are several different types of human feedback that can be used to guide RL agents. These include:

1. Demonstrations: In this type of feedback, a human provides examples of desirable behaviour by taking actions in the environment. The agent then attempts to mimic these actions to achieve the same goal.
2. Preferences: In preference-based feedback, the human provides information about which of two or more options is preferred. The agent then attempts to choose the option that is most preferred by the human.
3. Rewards: In reward-based feedback, the human provides a numerical reward signal to the agent based on its actions. The agent then attempts to maximise its cumulative reward over time.

Each of these types of feedback has its own strengths and weaknesses, and the choice of feedback type will depend on the specific problem being addressed.

Designing RLHF systems is not without its challenges. One of the main challenges is ensuring that the feedback provided by humans is accurate and consistent. Humans may be biased in their feedback, or may have different preferences and goals than the designer of the RL system. This can lead to suboptimal performance by the RL agent.

Another challenge is the trade-off between the amount of feedback provided and the cost of obtaining that feedback. In some cases, it may be impractical to obtain large amounts of feedback from humans, or the cost of doing so may be prohibitively high.

Finally, RLHF systems must be designed to work in real-world environments, where the agent must operate in a dynamic and constantly changing world. This can be difficult, as humans may not be able to anticipate all of the possible changes in the environment that the agent may encounter.

Despite these challenges, there has been significant progress in the field of RLHF in recent years. One of the most promising approaches is to combine multiple types of feedback to provide a more complete picture of the desired behaviour. For example, a system may use demonstrations to provide initial guidance to the agent, and then use preferences to fine-tune its behaviour over time.

Another approach is to use machine learning techniques to model the feedback provided by humans, and use this model to guide the behaviour of the RL agent. This can help to address issues of bias and inconsistency in human feedback, and can also reduce the amount of feedback required to achieve good performance.

In addition, there has been work on developing RLHF systems that can operate in complex and dynamic environments. For example, some systems use techniques from online learning to adapt to changes in the environment over time.