In-Context Multiple Instance Learning

2026-06-04

AI Summary

This work addresses the challenge of overfitting and poor generalization in multiple instance learning (MIL) under label-scarce conditions by proposing a context-based, fine-tuning-free approach. The method leverages a Perceiver architecture pretrained on diverse synthetic bag-structured datasets, integrating complementary inductive biases from varied generation strategies. This enables the model to perform accurate classification on new MIL tasks through a single forward pass with only a few labeled bags, without requiring any gradient-based adaptation. Evaluated across twelve established MIL benchmarks, the proposed approach consistently outperforms supervised baselines that rely on task-specific training, demonstrating substantially improved generalization and practical utility in few-shot MIL scenarios.

Abstract

Multiple Instance Learning (MIL) addresses problems where supervision is available at the level of bags of instances and has been successfully applied in fields ranging from computational pathology to satellite imagery. Nevertheless, existing algorithms struggle in the low-label regime that characterizes many real-world applications. Flexible models overfit and rigid ones fail to adapt to the task at hand. We show that pretraining an in-context learner with a Perceiver-style architecture on synthetic data yields a model that can solve new tasks from a handful of labeled bags. At inference time, classification happens in a single forward pass and requires no gradient updates. We propose and investigate different synthetic data generators for bag-structured data and find that they capture complementary inductive biases. A model pretrained on a mixture of these generators inherits their per-task strengths and achieves the best average performance across twelve MIL benchmarks, outperforming supervised baselines that require task-specific training.

Problem

• Multiple Instance Learning
• low-label regime
• overfitting
• model adaptability
• bag-structured data

Innovation

• In-Context Learning
• Multiple Instance Learning
• Perceiver Architecture
• Synthetic Data Generation
• Few-Shot MIL