The explanation for that is generally agreed on to have more to do with the aesthetics of early Christianity influencing Medieval practices, more than changes to human perception (source: I have a masters degree in Art History).
The explanation for that is generally agreed on to have more to do with the aesthetics of early Christianity influencing Medieval practices, more than changes to human perception (source: I have a masters degree in Art History).
That said, up until the European middle ages, nearly all art was that which was commissioned by the church. The style of the time permeated the art that wasn't commissioned by the church. As more non-religious art was commissioned, there was little need to remain working in that style and realism was embraced. I could be wrong, and probably am, but I think Catholicism is the only large Christian denomination that adopted realistic art.
I think depth was already understood by this point, though (see sculptures[2]). Again, I'm not OP, and I'm sure OP will have a more thorough explanation.
[0] https://orthodoxartsjournal.org/topics/iconography/
[1] https://www.britannica.com/event/Iconoclastic-Controversy
You can see the intent on many religious sculptures in medieval churches around e.g France: the technique is precise, so it’d be really easy for a sculptor to just compare and match to a living and breathing model, therefore they chose not to. Contemplating how churches tell stories through imagery, you can see how they used this style for emphasis on specific physical features to elicit strong emotional response instead, not entirely unlike those TVs in stores cranking up contrast to completely unrealistic levels.
You wouldn't want to draw mere mortals bigger than saints just because they happen to be closer. Peasants (which couldn't read and were the main target of these paintings) could get wrong ideas.
https://upload.wikimedia.org/wikipedia/commons/f/ff/Francesc...
[1] https://journals.sagepub.com/doi/10.1177/053901847000900411 - Church Time and Merchant Time in the Middle Ages - Jacques Le Goff