突破传统因果模型的单调性限制,实现更复杂场景下的反事实推理。
Counterfactual identifiability beyond global monotonicity: non-monotone triangular structural causal models
- 提出非单调三角结构因果模型,用机制可逆与上下文无关反向传输替代全局单调性
- 在合成数据和MuJoCo任务中,反事实恢复准确率显著提升,尤其在强非单调场景下
- 适用于机器人交互等复杂动态系统,适合研究因果推理与强化学习交叉的学者
结构因果模型为干预与反事实提供了统一语义,但多数可识别性结果依赖于全局单调性等强假设,这在具身交互中常被违反——相同外生扰动在不同接触情境下可能引发相反响应。本文探讨去除全局单调性后仍能保证可识别性的结构条件。提出非单调三角结构因果模型(NM-TM-SCM),保留三角递归结构,以机制级可逆性与上下文无关的反向传输替代全局单调性。证明这些条件等价于外生同构性,并蕴含完全反事实可识别性;给出反例表明局部可逆性不足。基于理论构建CausalInverter,采用三角可逆层、方向门控与传输稳定性正则化。在合成非单调机制上,结构偏差随非单调性增强带来系统性反事实性能提升;在MuJoCo Door任务中,模型实现事件级完美反事实恢复,连续角度误差低于Transformer基线,且恢复更稳定;在非单调性较弱的MuJoCo Push任务中,低数据条件下仍保持竞争力或更优,符合偏差-方差边界。结果揭示了介于全局单调三角模型与无约束黑箱世界模型之间的更广可识别域。
原文摘要 · Abstract (English)
Structural causal models provide a unified semantics for interventions and counterfactuals, but most identifiability results rely on restrictive assumptions like global monotonicity, which are often violated in embodied interaction, where the same exogenous perturbation can induce opposite responses under different contact contexts. We ask what structure still suffices once global monotonicity is dropped. We introduce non-monotone triangular structural causal models (NM-TM-SCM), which retain triangular recursion but replace global monotonicity with mechanism-wise invertibility and context-independent inverse transport. We prove that these conditions are equivalent to exogenous isomorphism and imply complete counterfactual identifiability, and we give a counterexample showing that local invertibility alone is insufficient. We instantiate the theory in CausalInverter, with triangular invertible layers, orientation gates, and transport-stability regularization. On synthetic non-monotonic mechanisms, the structural bias yields systematic counterfactual gains as non-monotonicity increases. On MuJoCo Door, our model achieves perfect event-level counterfactual recovery, lowers continuous angle error relative to a Transformer baseline, and delivers substantially more stable recovery than Transformer and conditional-flow predictors. On MuJoCo Push, where non-monotonicity is weaker, the same low-data predictors remain competitive or better, consistent with a bias-variance boundary. These results identify a broader identifiable regime between globally monotone triangular models and unconstrained black-box world models.
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