Recurrent Networks

Layer 1 · Intuition

Recurrent Networks

Why sequences (text, audio, time series) need networks with memory, and what an RNN intuitively does.

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An RNN processes a sequence one step at a time, carrying a hidden state forward as memory.

A plain feedforward network (MLP or CNN) processes a fixed-size input in one shot — it has no notion of 'order' or 'what came before.' But language, audio, and time series are inherently sequential: the meaning of a word depends heavily on the words before it. Recurrent neural networks (RNNs) were the first widely-used architecture built specifically to handle this.

The core idea: a running memory

An RNN processes a sequence one element at a time, maintaining a hidden state — a vector summarizing everything relevant it has seen so far. At each step, it combines the new input with its current hidden state to produce an updated hidden state, which then gets passed to the next step.

  1. h₀ (initial state)

  2. read x₁ → h₁

  3. read x₂ → h₂

  4. read x₃ → h₃

  5. output from final hₜ

The same set of weights is reused at every timestep, updating a running hidden state.

Check your understanding

4 questions · answer all to submit

  1. 1.What fundamental limitation of standard feedforward neural networks is addressed by Recurrent Neural Networks (RNNs)?

  2. 2.What conceptual role does the 'hidden state' play within a Recurrent Neural Network (RNN) architecture?

  3. 3.Regarding the weights in a recurrent neural network (RNN) across timesteps, which statement is accurate?

  4. 4.Prior to the widespread adoption of transformer architectures, which neural network architecture predominantly excelled in tasks such as machine translation and speech recognition?