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The Degenerative Effects of Training Large Language Models on Generated Data: A Cautionary Tale


Core Concepts
Training large language models on data generated by previous models leads to a degenerative process called "model collapse", where the models gradually forget the true underlying data distribution and converge to a narrow, biased representation.
Abstract
The paper discusses the phenomenon of "model collapse", a degenerative process that occurs when large language models (LLMs) are trained on data generated by previous iterations of the models. The key insights are: Model collapse is a universal effect that occurs across different generative models, including Gaussian Mixture Models, Variational Autoencoders, and LLMs. It is caused by two main sources of error: statistical approximation error from finite sampling, and functional approximation error from the model's inability to fully capture the true data distribution. In the case of discrete distributions, model collapse inevitably leads to the model converging to a delta function, losing all information about the original distribution. For single-dimensional Gaussians, the model's mean and variance diverge over generations, leading to a growing Wasserstein distance from the true distribution. Experiments on LLMs, specifically the OPT-125m model, show that even with fine-tuning on generated data, the models gradually start producing more probable sequences from the original data while introducing their own improbable sequences, indicating a shift in their perception of the underlying task. The implications are that preserving access to the original human-generated data is crucial to sustain the benefits of training LLMs on large-scale web data. Data generated by LLMs themselves will increasingly pollute the training data, making it harder to train subsequent generations of models without access to the original data sources.
Stats
"Training on generated data causes irreversible defects in the resulting models, where tails of the original content distribution disappear." "We find that use of model-generated content in training causes irreversible defects in the resulting models, where tails of the original content distribution disappear."
Quotes
"Model Collapse is a degenerative process affecting generations of learned generative models, where generated data end up polluting the training set of the next generation of models; being trained on polluted data, they then mis-perceive reality." "Access to the original data distribution is crucial: in learning where the tails of the underlying distribution matter, one needs access to real human-produced data."

Deeper Inquiries

How can we detect and mitigate model collapse in large language models before it becomes a significant issue?

Model collapse in large language models (LLMs) can have detrimental effects on their performance and the quality of generated content. To detect and mitigate model collapse in LLMs before it becomes a significant issue, several strategies can be employed: Monitoring Metrics: Regularly monitoring key metrics such as perplexity, diversity of generated outputs, and the distribution of generated data can provide early indicators of model collapse. Sudden shifts or stagnation in these metrics may signal the onset of model collapse. Diverse Training Data: Ensuring that the training data for LLMs is diverse and representative of the real-world distribution can help prevent model collapse. Incorporating data from various sources and domains can reduce the risk of the model converging to a limited set of outputs. Regular Retraining: Periodically retraining the LLM on fresh and diverse data can help prevent model collapse by introducing new patterns and information into the model. This can help counteract the effects of training on generated data from previous models. Regular Evaluation: Conducting regular evaluations of the model's performance on unseen data can help identify any signs of model collapse. If the model's performance deteriorates over time or shows inconsistencies, it may indicate model collapse. Enforcing Diversity: Implementing techniques such as diversity-promoting objectives during training can encourage the model to generate a wider range of outputs, reducing the likelihood of model collapse. Human-in-the-Loop Validation: Incorporating human validation and feedback loops can help identify and correct instances of model collapse. Human evaluators can provide insights into the quality and diversity of generated content. By implementing these strategies, researchers and developers can proactively detect and mitigate model collapse in LLMs, ensuring the continued effectiveness and reliability of these models.

What are the potential societal impacts of model collapse in LLMs, especially in terms of fairness and representation of marginalized groups?

Model collapse in large language models (LLMs) can have significant societal impacts, particularly in terms of fairness and representation of marginalized groups. Some potential societal impacts include: Bias Amplification: Model collapse can amplify existing biases present in the training data, leading to the perpetuation of stereotypes and discriminatory practices. This can further marginalize already vulnerable groups in society. Lack of Diversity: Model collapse can result in a lack of diversity in the generated content, limiting the representation of diverse voices and perspectives. This can reinforce existing power dynamics and exclude marginalized communities from the conversation. Misinformation and Harmful Content: If LLMs collapse and start generating inaccurate or harmful content, it can spread misinformation and contribute to the dissemination of harmful narratives that target marginalized groups. Underrepresentation: Model collapse may lead to underrepresentation of certain groups or topics in the generated content, further marginalizing those communities and hindering their visibility and recognition. Ethical Concerns: Model collapse raises ethical concerns regarding the responsible development and deployment of AI technologies. Ensuring that LLMs are trained and fine-tuned responsibly is crucial to prevent negative societal impacts. To address these potential societal impacts, it is essential to prioritize fairness, diversity, and ethical considerations in the development and deployment of LLMs. Implementing robust bias detection and mitigation strategies, promoting diversity in training data, and engaging with diverse stakeholders can help mitigate the negative consequences of model collapse on marginalized groups.

How might the insights from this work on model collapse apply to other domains beyond language models, such as generative models for images, audio, or other modalities?

The insights gained from studying model collapse in large language models (LLMs) can be extrapolated to other domains beyond language models, such as generative models for images, audio, and other modalities. Here are some ways in which these insights can be applied: Data Diversity: Just like in LLMs, ensuring diversity in training data is crucial for generative models in other domains. By incorporating a wide range of examples and patterns, the risk of model collapse can be reduced. Regular Evaluation: Similar to LLMs, regularly evaluating the performance of generative models for images, audio, or other modalities can help detect signs of model collapse. Monitoring key metrics and conducting thorough assessments can prevent the model from deteriorating over time. Human-in-the-Loop Validation: Implementing human validation and feedback loops can be beneficial for generative models in other domains. Human evaluators can provide insights into the quality, diversity, and accuracy of the generated outputs, helping to prevent model collapse. Bias Detection: Model collapse can exacerbate biases in generative models across different modalities. Techniques for bias detection and mitigation, as well as promoting fairness and diversity, are essential to address these issues. Ethical Considerations: Insights from studying model collapse in LLMs can inform ethical considerations in the development and deployment of generative models for images, audio, and other modalities. Prioritizing ethical practices and responsible AI development is crucial to mitigate potential societal impacts. By applying the lessons learned from model collapse in LLMs to generative models in other domains, researchers and developers can enhance the robustness, fairness, and reliability of AI systems across various modalities.
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