Wide Neural Networks Forget Less Catastrophically
Seyed-Iman MirzadehArslan ChaudhryDong YinHuiyi HuRazvan PascanuDilan GörürMehrdad Farajtabar
Demonstrates that increasing network width significantly reduces catastrophic forgetting in continual learning—even matching the benefits of replay buffers—and explains this phenomenon through gradient orthogonality, activation sparsity, and the lazy training regime.
Modern artificial intelligence increasingly relies on continuous data streams where models must absorb new information over time. A central barrier in these continual learning settings is catastrophic forgetting, where a network abruptly erases previously learned capabilities upon training on new tasks. While prior research focused almost exclusively on specialized algorithms or memory replay buffers to mitigate forgetting, relatively little is known about how the underlying network architecture itself influences memory retention.
The article demonstrates that increasing network width substantially and consistently reduces catastrophic forgetting in continual learning. Specifically, it evaluates how structural over-parametrization through width versus depth impacts task retention, overall accuracy, and underlying optimization dynamics.
To evaluate this relationship, the authors conducted empirical experiments across standard continual learning benchmarks, including Rotated MNIST (domain-incremental image classification across five tasks) using multi-layer perceptrons and Split CIFAR-100 (task-incremental classification across twenty tasks) using Wide Residual Networks. The study tested varying widths and depths across extensive hyperparameter sweeps and multiple random seeds. Beyond standard accuracy and forgetting metrics, the evaluation tracked optimization properties such as gradient angles across tasks, gradient sparsity, parameter displacement, and layer-wise gradient norms.
The investigation produced several key findings. First, expanding network width significantly reduces forgetting while improving overall accuracy: expanding a two-layer perceptron's width from 32 to 2048 reduced first-task forgetting from 62% to 48%, while scaling WideResNet width eightfold reduced forgetting from 42% to 31%. Second, wider models match or exceed the retention benefits achieved by dedicated replay buffers without sacrificing the model's plasticity on new tasks. Third, over-parametrization via depth produces no such benefit and frequently worsens forgetting due to exploding gradient norms in earlier layers. Fourth, wider networks achieve higher retention because their task gradients are more orthogonal, gradient updates are sparser, and the weights remain closer to their initialization throughout training. Finally, under a fixed parameter budget, shallow and wide networks consistently outperform deep and thin networks, and width benefits are fully additive when combined with dedicated continual learning algorithms.
These findings indicate that catastrophic forgetting is heavily governed by model architecture, not just training algorithms. Engineering teams facing sequential learning challenges can improve retention by deploying wider architectures rather than simply increasing network depth. However, relying solely on extreme width creates substantial trade-offs in computational cost, memory footprint, and energy consumption. Therefore, scaling width is most effectively viewed as a foundational architectural complement to existing algorithmic techniques rather than a standalone replacement.
For practical application, practitioners should prioritize wider, shallower designs when configuring neural backbones for streaming or continual learning tasks. System architects should also account for network capacity when benchmarking continual learning methods to avoid misattributing width-driven improvements to algorithmic designs. Future research should evaluate how other architectural mechanisms—such as activation functions, normalization layers, and vision transformers—interact with continual learning dynamics across larger-scale enterprise applications.
The conclusions are supported by consistent results across multi-seed runs, diverse architectures, and multiple benchmarks. However, the study focuses primarily on controlled classification benchmarks and highlights that full mathematical bounds on deep network gradients remain loose when singular values exceed one. Leaders should account for the increased training compute and inference latency of wide architectures before executing large-scale production deployments.
- Paper: Wide neural networks of any depth evolve as linear models under gradient descent, Jaehoon Lee et al. (2019). Its account of wide networks’ near-linear, lazy-training dynamics clarifies the width-dependent learning regime the source uses to interpret forgetting.
- Paper: A Continual Learning Survey: Defying Forgetting in Classification Tasks, Matthias De Lange et al. (2019). Its taxonomy of continual-learning methods and benchmarks supplies the field context for the source’s shift from algorithm design to model properties.
No sufficiently relevant recommendations were found.
