The perceptual generalization capabilities of Hebb's cell assembly

We rarely have trouble recognizing a familiar object.  So why is it 
so difficult to get a computer to do this?  But on closer inspection 
the mystery reverses itself.  What is amazing is not that a computer 
recognizes objects so poorly, but that we do it so well.  In contrast 
to the intuitive view, this is a complex and demanding problem, whose 
solution has far-ranging implications for how humans know the world.