I’m sure you’ve run across the Gestalt rules. These are rules of thumb about how we tell that objects go together. These are the most regularly mentioned:
We group by proximity, see that looks like 4 columns.
We group by shape. That’s 4 rows.
We groups by shape completion. See that looks like a single triangle instead of 3 pacman shapes. Is that 3 pacmans? Or 3 pacmen? I don’t know.
And that’s continuation. It looks like 2 crossing lines rather than 2 arrow-heads.
Yes, I know this is obvious. But what I’m saying is that your conscious experience of perception happens here, at the end of the perception process. And these object completion principles happen here, earlier.
It’s not just that you give hints to people by following rules, hints that “these 4 things go together”—it’s that if you break the principles, it’s as hard for people to see differently as it is to see my hand as a patchwork of colours, occlusion and edges.
Object completion will trump any principle which has to be thought about, no matter how rational.
And people do get it wrong.