Research map / Label-efficient and robust learning / Zero-/few-shot and meta-learning
Learning to Learn with Contrastive Meta-Objective
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Proposes ConML, a learner-agnostic contrastive meta-objective that uses task identity in mini-batch episodic meta-training to align models from the same task and discriminate models from different tasks in model space.
Problem
Meta-learners do not exploit the task identity available in mini-batch episodic training as supervision, which could improve generalization to unseen tasks.
Approach
Extends contrastive learning from representation space to model space: inner-task distance (alignment between models trained on subsets of the same task) minus inter-task distance (discrimination between models of different tasks in a batch), added to the episodic loss, with per-meta-learner mappings from models to vectors (weights, prototypes, hypernetwork outputs, or ICL probe outputs).
Key results
- On miniImageNet 5-way 1-shot, MAML improves from 48.75% to 56.25% and ProtoNet from 48.90% to 51.03% with ConML, using one shared configuration (B=32, K=1, lambda=0.1).
- Across 10 meta-learner/setting combinations in the mini/tieredImageNet table, ConML improves every reported accuracy, e.g. CAML 96.15% to 97.03% on miniImageNet 5-way 1-shot.
- In ICL on synthetic function classes, ConML reduces relative minimal error to 0.42-0.81 of baseline ICL, with shot savings of 3.9-11.3 examples.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| add ConML to LastShot | LastShot · miniImageNet 5-way 1-shot | accuracy (%): 64.80 ± 0.20 -> 66.24±0.72 | Helped |
| add ConML to LastShot | LastShot · miniImageNet 5-way 5-shot | accuracy (%): 81.65 ± 0.14 -> 83.29±0.45 | Helped |
| add ConML to LastShot | LastShot · tieredImageNet 5-way 1-shot | accuracy (%): 69.37±0.23 -> 71.82±0.70 | Helped |
| add ConML to LastShot | LastShot · tieredImageNet 5-way 5-shot | accuracy (%): 85.36 ±0.16 -> 87.05 ±0.49 | Helped |
| vary ConML subset sampling number from K=1 to K=16 (ablation) | MAML · miniImageNet 5-way 1-shot | accuracy (%): 56.25 -> 57.59 | Helped |
| vary ConML subset sampling number from K=1 to K=32 (ablation) | MAML · miniImageNet 5-way 1-shot | accuracy (%): 56.25 -> 57.33 | Helped |
| vary ConML subset sampling number from K=1 to K=32 (ablation) | ProtoNet · miniImageNet 5-way 1-shot | accuracy (%): 51.03 -> 52.48 | Helped |
| replace the naive contrastive loss with InfoNCE (ablation) | ConML · few-shot image classification | accuracy | Helped |
| use Euclidean rather than cosine distance (ablation) | ConML with ProtoNet · few-shot image classification | accuracy | Helped |
Surprising findings
- Euclidean distance works much better than cosine for ProtoNet, while cosine works generally for other learners.
- The paper reports that the naive contrastive loss can cause model collapse when lambda is set too high.
Limitations
- Memory cost grows linearly with K, roughly 2x memory versus the baseline at K=1.
- The theoretical guarantee relies on strong assumptions such as unit-norm model representations and a specific distance choice, and the paper notes the squared-cosine form was not implemented in experiments.
- Few-shot experiments for some baselines lack error bars, and compute resources are not reported in detail.
Experimental setup
Datasets: miniImageNet tieredImageNet Meta-Dataset
Benchmarks: miniImageNet tieredImageNet Meta-Dataset
Metrics: accuracy relative minimal error shot spare memory relative time
Baselines: MAML FOMAML Reptile MatchNet ProtoNet SCNAPs CAML MELR LastShot P>M>F
Builds on: MAML ProtoNet CAML Simple CNAPS InfoNCE
Closest papers by meaning
- The Close Relationship Between Contrastive Learning and Meta-Learning (ICLR 2022 · similarity 0.91)
- Function Contrastive Learning of Transferable Meta-Representations (ICML 2021 · similarity 0.88)
- Meta-Learning Requires Meta-Augmentation (NeurIPS 2020 · similarity 0.88)
- Any-Way Meta Learning (AAAI 2024 · similarity 0.88)
- Provable Meta-Learning with Low-Rank Adaptations (NeurIPS 2025 · similarity 0.87)
- Task Groupings Regularization: Data-Free Meta-Learning with Heterogeneous Pre-trained Models (ICML 2024 · similarity 0.87)
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