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Zachary Chase Lipton

35 accepted papers

2026

LLMs Struggle to Balance Reasoning and World Knowledge in Causal Narrative Understanding

ICLR 2026poster

The ability to robustly identify causal relationships is essential for autonomous decision-making and adaptation to novel scenarios. However, accurately inferring causal structure requires integrating both world knowledge and abstract logical reasoning. In this work, we investigate the interaction b…

Cited by 0SourceScholar
2025

OpenUnlearning: Accelerating LLM Unlearning via Unified Benchmarking of Methods and Metrics

NeurIPS 2025poster

Robust unlearning is crucial for safely deploying large language models (LLMs) in environments where data privacy, model safety, and regulatory compliance must be ensured. Yet the task is inherently challenging, partly due to difficulties in reliably measuring whether unlearning has truly occurred.…

Cited by 0SourcecodeScholar
2025

Position: Towards Bidirectional Human-AI Alignment

NeurIPS 2025poster

Recent advances in general-purpose AI underscore the urgent need to align AI systems with human goals and values. Yet, the lack of a clear, shared understanding of what constitutes "alignment" limits meaningful progress and cross-disciplinary collaboration. In this position paper, we argue that the…

Cited by 0SourceScholar
2025

Safety Pretraining: Toward the Next Generation of Safe AI

NeurIPS 2025poster

As large language models (LLMs) are increasingly deployed in high-stakes settings, the risk of generating harmful or toxic content remains a central challenge. Post-hoc alignment methods are brittle: once unsafe patterns are learned during pretraining, they are hard to remove. In this work, we prese…

Cited by 0SourceScholar
2025

Towards characterizing the value of edge embeddings in Graph Neural Networks

ICML 2025poster

Graph neural networks (GNNs) are the dominant approach to solving machine learning problems defined over graphs. Despite much theoretical and empirical work in recent years, our understanding of finer-grained aspects of architectural design for GNNs remains impoverished. In this paper, we consider t…

Cited by 1SourcePDFScholar
2025

Valid Inference with Imperfect Synthetic Data

NeurIPS 2025poster

Predictions and generations from large language models are increasingly being explored as an aid in limited data regimes, such as in computational social science and human subjects research. While prior technical work has mainly explored the potential to use model-predicted labels for unlabeled dat…

Cited by 0SourceScholar
2024

A theoretical case-study of Scalable Oversight in Hierarchical Reinforcement Learning

NeurIPS 2024poster

A key source of complexity in next-generation AI models is the size of model outputs, making it time-consuming to parse and provide reliable feedback on. To ensure such models are aligned, we will need to bolster our understanding of scalable oversight and how to scale up human feedback. To this end…

Cited by 0SourcePDFScholar
2024

Medical Adaptation of Large Language and Vision-Language Models: Are We Making Progress?

EMNLP 2024main

Several recent works seek to develop foundation models specifically for medical applications, adapting general-purpose large language models (LLMs) and vision-language models (VLMs) via continued pretraining on publicly available biomedical corpora. These works typically claim that such domain-adapt…

2024

Post-Hoc Reversal: Are We Selecting Models Prematurely?

NeurIPS 2024poster

Trained models are often composed with post-hoc transforms such as temperature scaling (TS), ensembling and stochastic weight averaging (SWA) to improve performance, robustness, uncertainty estimation, etc. However, such transforms are typically applied only after the base models have already been f…

2024

Rethinking LLM Memorization through the Lens of Adversarial Compression

NeurIPS 2024poster

Large language models (LLMs) trained on web-scale datasets raise substantial concerns regarding permissible data usage. One major question is whether these models "memorize" all their training data or they integrate many data sources in some way more akin to how a human would learn and synthesize i…

Cited by 40SourcePDFScholar
2024

T-MARS: Improving Visual Representations by Circumventing Text Feature Learning

ICLR 2024poster

Large web-crawled multimodal datasets have powered a slew of new methods for learning general-purpose visual representations, advancing the state of the art in computer vision and revolutionizing zero- and few-shot recognition. One crucial decision facing practitioners is how, if at all, to curate t…

2024

The Fragility of Fairness: Causal Sensitivity Analysis for Fair Machine Learning

NeurIPS 2024poster

Fairness metrics are a core tool in the fair machine learning literature (FairML), used to determine that ML models are, in some sense, “fair.” Real-world data, however, are typically plagued by various measurement biases and other violated assumptions, which can render fairness assessments meaningl…

2024

Time-Varying Propensity Score to Bridge the Gap between the Past and Present

ICLR 2024poster

Real-world deployment of machine learning models is challenging because data evolves over time. While no model can work when data evolves in an arbitrary fashion, if there is some pattern to these changes, we might be able to design methods to address it. This paper addresses situations when data ev…

Cited by 2SourcePDFScholar
2024

Understanding Hallucinations in Diffusion Models through Mode Interpolation

NeurIPS 2024poster

Colloquially speaking, image generation models based upon diffusion processes are frequently said to exhibit ''hallucinations'' samples that could never occur in the training data. But where do such hallucinations come from? In this paper, we study a particular failure mode in diffusion models, whi…

2023

CHiLS: Zero-Shot Image Classification with Hierarchical Label Sets

ICML 2023poster

Open vocabulary models (e.g. CLIP) have shown strong performance on zero-shot classification through their ability generate embeddings for each class based on their (natural language) names. Prior work has focused on improving the accuracy of these models through prompt engineering or by incorporati…

2023

Can Neural Network Memorization Be Localized?

ICML 2023poster

Recent efforts at explaining the interplay of memorization and generalization in deep overparametrized networks have posited that neural networks *memorize* ``hard'' examples in the final few layers of the model. Memorization refers to the ability to correctly predict on *atypical* examples of the t…

2023

Complementary Benefits of Contrastive Learning and Self-Training Under Distribution Shift

NeurIPS 2023poster

Self-training and contrastive learning have emerged as leading techniques for incorporating unlabeled data, both under distribution shift (unsupervised domain adaptation) and when it is absent (semi-supervised learning). However, despite the popularity and compatibility of these techniques, their ef…

Cited by 17SourcePDFScholar
2023

Deep Equilibrium Based Neural Operators for Steady-State PDEs

NeurIPS 2023poster

Data-driven machine learning approaches are being increasingly used to solve partial differential equations (PDEs). They have shown particularly striking successes when training an operator, which takes as input a PDE in some family, and outputs its solution. However, the architectural design space,…

Cited by 7SourcePDFScholar
2023

Disentangling the Mechanisms Behind Implicit Regularization in SGD

ICLR 2023poster

A number of competing hypotheses have been proposed to explain why small-batch Stochastic Gradient Descent (SGD) leads to improved generalization over the full-batch regime, with recent work crediting the implicit regularization of various quantities throughout training. However, to date, empirical…

2023

Model-tuning Via Prompts Makes NLP Models Adversarially Robust

EMNLP 2023long main

In recent years, NLP practitioners have converged on the following practice: (i) import an off-the-shelf pretrained (masked) language model; (ii) append a multilayer perceptron atop the CLS token's hidden representation (with randomly initialized weights); and (iii) fine-tune the entire model on a d…

Cited by 0SourcecodeScholar
2023

Neural Network Approximations of PDEs Beyond Linearity: A Representational Perspective

ICML 2023poster

A burgeoning line of research has developed deep neural networks capable of approximating the solutions to high dimensional PDEs, opening related lines of theoretical inquiry focused on explaining how it is that these models appear to evade the curse of dimensionality. However, most theoretical anal…

Cited by 12SourcePDFScholar
2023

Online Label Shift: Optimal Dynamic Regret meets Practical Algorithms

NeurIPS 2023spotlight

This paper focuses on supervised and unsupervised online label shift, where the class marginals $Q(y)$ varies but the class-conditionals $Q(x|y)$ remain invariant. In the unsupervised setting, our goal is to adapt a learner, trained on some offline labeled data, to changing label distributions given…

2023

RLSbench: Domain Adaptation Under Relaxed Label Shift

ICML 2023poster

Despite the emergence of principled methods for domain adaptation under label shift, their sensitivity to shifts in class conditional distributions is precariously under explored. Meanwhile, popular deep domain adaptation heuristics tend to falter when faced with label proportions shifts. While seve…

2023

USB: A Unified Summarization Benchmark Across Tasks and Domains

EMNLP 2023long findings

While the NLP community has produced numerous summarization benchmarks, none provide the rich annotations required to simultaneously address many important problems related to control and reliability. We introduce a Wikipedia-derived benchmark, complemented by a rich set of crowd-sourced annotatio…

Cited by 0SourcecodeScholar
2022

Characterizing Datapoints via Second-Split Forgetting

NeurIPS 2022accept

Researchers investigating example hardness have increasingly focused on the dynamics by which neural networks learn and forget examples throughout training. Popular metrics derived from these dynamics include (i) the epoch at which examples are first correctly classified; (ii) the number of times th…

2022

Domain Adaptation under Open Set Label Shift

NeurIPS 2022accept

We introduce the problem of domain adaptation under Open Set Label Shift (OSLS), where the label distribution can change arbitrarily and a new class may arrive during deployment, but the class-conditional distributions $p(x|y)$ are domain-invariant. OSLS subsumes domain adaptation under label shift…

2022

Leveraging unlabeled data to predict out-of-distribution performance

ICLR 2022poster

Real-world machine learning deployments are characterized by mismatches between the source (training) and target (test) distributions that may cause performance drops. In this work, we investigate methods for predicting the target domain accuracy using only labeled source data and unlabeled target d…

2022

Unsupervised Learning under Latent Label Shift

NeurIPS 2022accept

What sorts of structure might enable a learner to discover classes from unlabeled data? Traditional approaches rely on feature-space similarity and heroic assumptions on the data. In this paper, we introduce unsupervised learning under Latent Label Shift (LLS), where the label marginals $p_d(y)$ shi…

Cited by 10SourcePDFScholar
2021

Efficient Online Estimation of Causal Effects by Deciding What to Observe

NeurIPS 2021spotlight

Researchers often face data fusion problems, where multiple data sources are available, each capturing a distinct subset of variables. While problem formulations typically take the data as given, in practice, data acquisition can be an ongoing process. In this paper, we introduce the problem of deci…

2021

Explaining the Efficacy of Counterfactually Augmented Data

ICLR 2021poster

In attempts to produce machine learning models less reliant on spurious patterns in NLP datasets, researchers have recently proposed curating counterfactually augmented data (CAD) via a human-in-the-loop process in which given some documents and their (initial) labels, humans must revise the text to…

Cited by 84SourcePDFScholar
2021

Mixture Proportion Estimation and PU Learning:A Modern Approach

NeurIPS 2021spotlight

Given only positive examples and unlabeled examples (from both positive and negative classes), we might hope nevertheless to estimate an accurate positive-versus-negative classifier. Formally, this task is broken down into two subtasks: (i) Mixture Proportion Estimation (MPE)---determining the fract…

2021

Off-Policy Risk Assessment in Contextual Bandits

NeurIPS 2021poster

Even when unable to run experiments, practitioners can evaluate prospective policies, using previously logged data. However, while the bandits literature has adopted a diverse set of objectives, most research on off-policy evaluation to date focuses on the expected reward. In this paper, we introduc…

Cited by 41SourcePDFScholar
2021

Parametric Complexity Bounds for Approximating PDEs with Neural Networks

NeurIPS 2021spotlight

Recent experiments have shown that deep networks can approximate solutions to high-dimensional PDEs, seemingly escaping the curse of dimensionality. However, questions regarding the theoretical basis for such approximations, including the required network size remain open. In this paper, we investig…

Cited by 26SourcePDFScholar
2021

Rebounding Bandits for Modeling Satiation Effects

NeurIPS 2021poster

Psychological research shows that enjoyment of many goods is subject to satiation, with short-term satisfaction declining after repeated exposures to the same item. Nevertheless, proposed algorithms for powering recommender systems seldom model these dynamics, instead proceeding as though user prefe…

Cited by 30SourcePDFScholar