A classification head is the task-specific ending of a neural network: it receives learned representations and turns them into class predictions. The earlier network can remain a reusable backbone, while the head adapts it to a particular classification problem. section 15.4.2 section 8.3.1
IMDb sentiment classification
A RoBERTa backbone produces a sequence of contextual token representations. Selecting the first token's representation supplies one vector per review; dropout and a 768-unit ReLU Dense layer refine it, and a final Dense layer with one sigmoid output predicts the binary label. section 15.4.4
A practical classification head commonly involves:
- Condense the backbone output to one representation per sample, using contextual first-token selection for RoBERTa or global average pooling for convolutional features. section 15.4.4
- Treat the head as a tunable design choice: vary representation-layer count, unit count, activation, or loss and compare validation and test accuracy. section 4.1.6

