But the task you are asked to perform is “count the passes.” If I let my eyes focus on the other things, see a gorilla, and say to myself, “Wow, there is a gorilla!” then in those seconds, I am not paying attention to the very thing I was asked to do which is count the passes.
But most people do think it’s remarkable that they didn’t see it. YMV.
It translates to eyewitness testimony because we have no idea what details the person was actually paying close attention to, and the witness is often not aware of the effects this attention has on their memories of what happened. In the gorilla scene, if we ask most people “was there a gorilla in the room,” they’ll answer with a very firm “no.” Most people won’t say “well I wasn’t paying attention to anything but how many times the ball was passed” because it wouldn’t even occur to them to think that paying attention to ball passing would make them miss something like that gorilla in that video. As the OP says, to many it even seems practically impossible for anyone to have missed that, even given the setup.
That’s where our remarkable pattern-recognition skills come in handy - we see, evaluate, and discard before we even consciously know we’ve seen something.
I do appreciate how well this illustrates that you don’t see or pay attention to or remember things that you could reasonably expect to have noticed. We truly have no idea what goes on between the sensory input that comes in through our senses and what our brain lets us (the consciousness riding this body) know.
There are others where something else than a gorilla appears. There’s one with the gorilla, but made with the expectation that many people will be aware of it hence including something equally outrageous (can’t remember what) besides the gorilla, that people don’t notice. There’sthis one, which is quite different in nature, too.
I was busy counting the passes, which I missed by one dammit!, when I suddenly noticed the gorilla in the middle, wondered what the hell it was doing there, and then didn’t notice it was gone.
I teach English as a second language, including to kindergarten kids, and you can really see how distracted they become by people coming and going.
It isn’t a pass/fail thing though, it is merely an illustration of how fallible we all are.
If I described this task to you, start to finish, without you ever having seen it or knowing about it, how confident would you be that an average person would spot something as obvious as a gorilla? The fact that a majority of people don’t see it is a powerful and yet simple illustration of attention blindness and that is a critical point to understand if we are to understand the way people behave and why they sometimes do superficially stupid things.