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Decision-Making in Large Language Models

Examining how LLMs learn and make choices based on rewards.

― 5 min read


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Large language models (LLMs) are advanced computer programs designed to understand and generate text. They are like very complex versions of search engines that can write, translate, or answer questions. Recently, researchers have looked at how these models not only respond to prompts but also learn to make decisions that maximize rewards, similar to how humans make choices based on past outcomes.

Learning Through Context

One interesting ability of LLMs is known as In-context Learning. This allows them to learn to perform various tasks just by looking at examples or following instructions without needing additional training. This feature is particularly prominent in larger models that have been trained on vast amounts of text, making them more capable of learning from fewer examples.

When LLMs are used in Decision-making roles, it becomes crucial to understand their learning processes. This includes looking at how they make choices that aim to maximize rewards when faced with different options, especially in situations that can resemble gambling or strategic games.

The Bandit Task Concept

To study decision-making, researchers often use a type of task called a bandit task. In these tasks, there are multiple options, much like slot machines in a casino, where each option has a different chance of providing a reward. The goal is to learn which options yield the best results and to choose them consistently.

For example, in a simple bandit task, you might have two slot machines: one that pays off more often than the other. Through trial and error, a decision-maker would learn to pick the slot machine that pays off more frequently. In this study, Bandit Tasks were adapted for LLMs to see if they would show similar behavior to humans.

Experiment Design

Researchers carried out experiments with several types of bandit tasks, where each task involved making choices between different slot machines. The LLMs were presented with pairs or groups of options, and their performance was measured in terms of how well they picked the options that provided the best rewards.

The experiments varied in structure, with some tasks having two options and others having three. The researchers focused on how LLMs learned about rewards and whether their choices were influenced by the context in which those choices were presented. This context is important because it can significantly affect decision-making.

The Role of Feedback

In these tasks, the models received feedback after each choice, helping them learn which options were better. The feedback would tell them whether they had made a good choice by choosing an option that led to a higher reward or a poor choice if the option yielded less.

The researchers specifically wanted to see if LLMs demonstrated biases in their decision-making, similar to how humans often favor certain options based on context. For example, if a model learns that one option is better than another in a particular context, will it continue to favor that option even when tested in a different context?

Results Overview

The results showed that the LLMs could generally pick the right options based on the rewards they learned about during training. Most LLMs performed above chance levels, meaning they were able to learn which options were better than random guessing. However, the models also showed signs of a relative value bias, leading them to favor certain options based on past experiences, even when those options were not the best choice in a new scenario.

Interestingly, while explicit comparisons between options improved the models’ performance in training, they hindered the models' ability to generalize this learning to new situations. This is similar to human behavior, where people may struggle to apply what they learned in one situation to a different context.

Insights from the Models

To understand how LLMs make these decisions, researchers used simple mathematical models to describe their behavior. These models helped to show that the decisions made by LLMs were not random but followed certain patterns that could be explained by how they encoded the values of different options.

The findings indicated that LLMs process relative values-their perceived value of an option based on how it compares to others-and this processing appears to be a learned behavior. The models were more likely to choose options that had better relative values when the choices were explicitly compared, which further illustrated the biases present in their decision-making.

Implications for Real-World Applications

These findings have significant implications for how LLMs might be used in various applications. If LLMs are prone to biases based on relative value processing, it could lead to suboptimal decision-making in critical areas like finance, healthcare, or other domains where accurate outcomes are essential.

Understanding these biases is crucial for designing better decision-making systems using LLMs. Enhancing their ability to generalize learned values across different contexts could improve their effectiveness and reliability.

Future Directions in Research

Future research should explore new methods to reduce biases in LLM decision-making. This might include developing better training processes or experimenting with different prompting techniques to enhance learning. For example, instructing models to evaluate expected payoffs before making choices might significantly help reduce biases.

Researchers also need to expand their investigations to include more types of LLMs and different learning tasks. By doing so, they can gain a more comprehensive view of how biases arise and how they can be addressed effectively.

Conclusion

Large language models exhibit complex behaviors in learning and decision-making, showing patterns similar to human biases. Their ability to learn from context, while powerful, also leads to challenges in applying that knowledge across different situations. Understanding these dynamics is essential for leveraging LLMs effectively in real-world decision-making scenarios and improving their design in the future.

Through further research, we can better grasp the workings of these models and refine them to produce more accurate and unbiased outcomes, ultimately enhancing their utility in various fields.

Original Source

Title: Large Language Models are Biased Reinforcement Learners

Abstract: In-context learning enables large language models (LLMs) to perform a variety of tasks, including learning to make reward-maximizing choices in simple bandit tasks. Given their potential use as (autonomous) decision-making agents, it is important to understand how these models perform such reinforcement learning (RL) tasks and the extent to which they are susceptible to biases. Motivated by the fact that, in humans, it has been widely documented that the value of an outcome depends on how it compares to other local outcomes, the present study focuses on whether similar value encoding biases apply to how LLMs encode rewarding outcomes. Results from experiments with multiple bandit tasks and models show that LLMs exhibit behavioral signatures of a relative value bias. Adding explicit outcome comparisons to the prompt produces opposing effects on performance, enhancing maximization in trained choice sets but impairing generalization to new choice sets. Computational cognitive modeling reveals that LLM behavior is well-described by a simple RL algorithm that incorporates relative values at the outcome encoding stage. Lastly, we present preliminary evidence that the observed biases are not limited to fine-tuned LLMs, and that relative value processing is detectable in the final hidden layer activations of a raw, pretrained model. These findings have important implications for the use of LLMs in decision-making applications.

Authors: William M. Hayes, Nicolas Yax, Stefano Palminteri

Last Update: 2024-05-18 00:00:00

Language: English

Source URL: https://arxiv.org/abs/2405.11422

Source PDF: https://arxiv.org/pdf/2405.11422

Licence: https://creativecommons.org/licenses/by/4.0/

Changes: This summary was created with assistance from AI and may have inaccuracies. For accurate information, please refer to the original source documents linked here.

Thank you to arxiv for use of its open access interoperability.

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