Let me start with a confession. Classifiers are hard. Not hard in the way vocabulary is hard, where you simply need more exposure, more repetition, more time. Classifiers are hard because they require signers to think spatially while signing temporally, to track multiple referents while producing new content, to select among productive options while maintaining discourse coherence.
That mouthful of a sentence appears in the opening of Depicting Space, and I want to unpack it for you, because hidden inside that description is something important about human cognition.
When you speak English, your words unfold in time. One after another. Linear. Sequential. The sentence has a beginning, a middle, an end. You cannot say two words simultaneously. The channel is narrow.
But when you sign ASL, something different happens. Your hands can represent two entities at once. Your face carries grammatical information independent of your hands. Your body can shift to become a character while your hands continue to manipulate objects in observer space. The channel is wide. Parallel processing becomes possible.