arXiv:2607.04333cs.LG2026-07

通过结构化先验干预,证明泛化延迟本质是形成正确表征所需时间。

Structure-Specific Representational Priors Causally Control the Grokking Delay

  • 用对比损失注入不同结构先验,控制变量验证表征结构影响
  • 仅真实结构能加速泛化,最快提升22倍,且与权重范数相关
  • 通过范数钳制可稳定加速,适合需快速泛化的模型训练场景

Grokking——在训练集过拟合后仍长期延迟实现泛化——已被无结构干预(如梯度过滤、权重范数钳制、几何惩罚)加速。但这一延迟是否特指形成任务结构化表征所需时间,此前仅为观察。我们通过因果实验,在单层Transformer学习模加法任务时,利用监督对比损失注入三种内容不同的表征先验:(i) 真实结构((a+b) mod p),(ii) 逻辑一致但错误的兄弟结构((a−b) mod p),(iii) 随机划分(仅可记忆)。三者具有相同损失形式、强度、类别规模和几何结构。结果显示泛化出现概率呈清晰梯度:真实结构22/30次成功,兄弟结构14/15次,随机结构0/20次(Fisher检验p=1.3×10⁻⁷)。一个与权重范数匹配的对照实验在交叉熵上重现范数轨迹,泛化率为0/15,排除范数为中介。探测显示结构形成早于且可预测泛化。只有真实结构能加速grokking(最高达2.75倍),且具有剂量依赖性和双峰特征。进一步预测验证:因加速受权重范数副作用调控,训练中钳制范数可实现稳定、独立的加速,中位速度提升8.6倍(最快种子达22倍,1000轮内),并随范数降低单调增长;残差停滞现象也消失(整体比较显著,0/40对6/20,p=7.7×10⁻⁴),但非单一方法显著。因此,grokking延迟因果上即为形成正确表征结构的时间,由特征层面决定而非标签层面。

原文摘要 · Abstract (English)

Grokking -- generalization long after training-set interpolation -- has been accelerated by structure-agnostic interventions (gradient filtering, weight-norm clamping, geometric penalties). Whether the delay specifically measures the time to form task-structured representations has remained observational. We test it causally by injecting representational priors of varying content into a one-layer transformer learning modular addition, via a supervised-contrastive loss whose positives encode (i) the task's true structure ($(a+b) \bmod p$), (ii) a coherent-but-wrong sibling ($(a-b) \bmod p$), or (iii) a random partition -- all with identical loss form, strength, class sizes, and geometry. Whether generalization occurs follows a clean gradation: true 22/30 runs, sibling (same periodic features, wrong combination) 14/15, random (only memorizable) 0/20 (Fisher $p=1.3\times10^{-7}$). A weight-norm-matched control replaying the norm trajectory onto plain cross-entropy generalizes 0/15, ruling out the norm as mediator. Probes show structure formation precedes and predicts generalization in all runs. Only the true structure also accelerates grokking (up to $2.75\times$), but this is dose-dependent and bimodal. We then confirm the mechanism by prediction: because the acceleration is gated by a weight-norm side-effect, clamping the norm during training yields a reliable, standalone accelerator with a median $8.6\times$ speedup (up to $22\times$ on the fastest seeds, under 1000 epochs), growing monotonically as the norm is held lower; the residual stalls also vanish, though significant only pooled over the two mitigations run at both strengths ($0/40$ vs $6/20$, $p=7.7\times10^{-4}$), not per method. The grokking delay is, causally, the time to form the right representational structure -- decided at the level of features, not labels.

深度学习表征学习泛化机制因果推理

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