Well in the end we are just trying to explain by a shapeshifter with limitless potential is adopting human characteristics defined by the limitations of a human actor.
He has no sense of taste or smell, that is clearly established. I always thought maybe it could be some sort of extrasensory hearing and echo displacement, kinda like bats use and he just learned to recognize the various details that define who's who such as facial features and what not. It doesn't exactly stand up to scrutiny but it would explain attention spans similar to fields of vision and what not. There is some sort of sixth sense thing going on there since a blob of gew can be aware of you somehow.