The amoebae categorizes. 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.