order to come up with an algorithm to learn features let's turn one last time to biological motivation turns out that when your brain gets an image the first thing it does is look for edges in the image right so first stage of visual processing on the brain is called visual cortical area view what I think y'all might have mentioned is yesterday and the first thing it does is look for edges or lines I'm going to use the term lines and edges interchangeably so in your brain right now there's probably a neuron that is looking for a 45 degree