Dual-Domain Division Multiplexer for General Continual Learning: A Pseudo Causal Intervention Strategy

Abstract

As a continual learning paradigm where non-stationary data arrive in the form of streams and training occurs whenever a small batch of samples is accumulated, general continual learning (GCL) suffers from both inter-task bias and intra-task bias. Existing GCL methods can hardly simultaneously handle two issues since it requires models to avoid from lying into the spurious correlation trap of GCL. From a causal perspective, we formalize a structural causality model of GCL and conclude that spurious correlation exists not only between confounders and input, but also within multiple causal variables. Inspired by frequency transformation techniques which harbor intricate patterns of image comprehension, we propose a plug-and-play module: the Dual-Domain Division Multiplex (D3M) unit, which intervenes confounders and multiple causal factors over frequency and spatial domains with a two-stage pseudo causal intervention strategy. Typically, D3M consists of a frequency division multiplexer (FDM) module and a spatial division multiplexer (SDM) module, each of which prioritizes target-relevant causal features by dividing and multiplexing features over frequency domain and spatial domain, respectively. As a lightweight and model-agonistic unit, D3M can be seamlessly integrated into most current GCL methods. Extensive experiments on four popular datasets demonstrate that D3M significantly enhances accuracy and diminishes catastrophic forgetting compared to current methods. The code is available at https://github.com/wangsfan/D3M.