It can tell food from non-food chemically. That is a simple form of categorization. There are 100 million fiber coming out of your retina and only 1 million going to the brain. There's a reduction of 100 to 1. Categorization is what's happening.
Categorization occurs whenever lots of inputs are boiled down to a single output.
This happens outside the retina and everywhere else in the brain, wherever a number of neurons give output to another neuron. Wherever there is a reduction of information, categorization occurs. Categorization is not just in language. All neural beings categorize. In some philosophical traditions, the belief is that we are supposed to rise above our categorizations and see the world as it really it, but this is impossible for neural beings.