Incorrect! You can glance & see a large shape you ASSUME is a car. You need to pause & look at the door mirror to actually see any vehicle. Drive a car on the road with a lot of sponsorship decals or a painted design on the front & you realise the typical standard of observation on the roads is non-existent.
Why does the internet demand that people narrow their point down to such an exact level of reasoning before anyone will accept it? You've expanded my point and clarified it, you haven't rendered it incorrect.
Our brain will process many things on auto pilot. Noticing things that we expect to be there is one of these instances. There's no relevant, quotable science here but I think most would agree that given 100 glances at a door mirror you'd expect to spot an object that you expect to see, close to 100% of the time*. Asked 100 times 'Was there a car there' or 'What colour was the car' we'd all be spot on. Asked 'What colour was the pram crossing the road' I'm sure we'd all fail.
The problem is that most people are pre-conditioned to automatically see large shapes as they represent danger. Currently, there is no visible campaign to highlight the danger that doors pose to cyclists, in the way that there has been for say, properly looking at junctions for motorcycles, for example.
There should be a campaign to highlight the dangers. It's an extra 5 seconds to properly look. It should happen. Every single time.
* = I know the 'most of the time' opens the door to accidents, but that's always going to be the case. Infallibility in any human based system is impossible.