What happens to layers whose training gradients vanish?

They train very slowly or not at all.

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  1. They double in width
  2. They barely train ✔
  3. They tokenize inputs

Why: Deep backpropagation can multiply many small derivative terms. The resulting near-zero gradient gives early layers almost no useful update signal.

Huh, didn't know that: Vanishing gradients are especially troublesome when learning dependencies across many recurrent time steps.

The dad joke
The gradient vanished before paying the loss.
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References

Answer: They barely train. Deep backpropagation can multiply many small derivative terms. The resulting near-zero gradient gives early layers almost no useful update signal.

  1. Google Machine Learning Crash Course: Backpropagation developers.google.com/machine-learning/crash-course/neural-networks/backpropagation
    Layers with vanishing gradients train very slowly, or not at all.
    Checked 2026-10-10.

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