[1610.01644] Understanding intermediate layers using linear classifier probes • /r/MachineLearning

Have people not been doing this up till now? Seems fairly obvious to me. A similar technique I've used for fun is applying k-NN to each layer to see how well the classes are separated at this layer based on the Euclidean distance (or whatever other metric one wishes to employ). Note that technically k-NN doesn't need any training at all!