Possibly-related, I wrote much of my undergraduate thesis on how experts (or rather, just people with lots of experience in a field) see or hear differences where non-experts see none.
To a regular person, the cloaca of male and female baby chicks look identical, but to a chicken sexer who sorts hundreds of baby chicks a day, they look totally different, even if the person can't describe exactly how. To expert radiologists, a shadow in an x-ray is almost certainly cancer, while a non-expert can't see any shadow at all.
Similarly, and more mundanely, in languages where there isn't a strong meaningful distinction between two sounds, speakers have trouble discerning them. To a monolingual native Japanese person, /r/ and /l/ sound almost identical, while a native English speaker can't understand how they don't hear the difference. To a French person, the "oo" sounds in au dessus (on top) and au dessous (underneath) sound completely different, yet to an English person they are almost indistinguishable.
These are really the same phenomena, and why an expert bird watcher would have no trouble recognizing the "sack of potatoes" flight of a bird.