Prototype Learning

Prototype Learning is an interpretable ML approach where the model learns a set of representative examples (prototypes) and classifies new inputs based on their similarity to these prototypes — providing explanations of the form "this looks like prototype X" which are naturally intuitive.

How Prototype Learning Works

• Prototypes: The model learns $k$ prototype feature vectors per class during training.
• Similarity: For a new input, compute similarity (L2 distance, cosine) to all prototypes in the learned feature space.
• Classification: Predict the class based on weighted similarities to prototypes.
• Visualization: Each prototype can be projected back to input space or matched to nearest real examples.

Why It Matters

• Natural Explanations: "This is class A because it looks like prototype A3" — matches human reasoning.
• ProtoPNet: Prototypical Part Networks learn part-based prototypes — "this bird has a beak like prototype X."
• Trustworthy AI: Prototype-based explanations are more intuitive than feature attribution methods.

Prototype Learning is classification by example — explaining predictions through similarity to learned representative examples that humans can examine.