No Upside-Down, o quanto você vê / ouve do mundo normal?

Em Stranger Things, no início da série,

Joyce finds a way to communicate with her missing son Will, using electric lights and an alphabet pointed on the wall (where Will spells out his answers by activating the lights).

No entanto, mais tarde, quando realmente vemos mais do Upside-Down ...

The environment seems to be relatively static, and as far as I could tell, completely empty of people. And, as far as I could tell (from the scenes that cut between the two perspectives in real time), the Christmas lights were not visible from the Upside Down. I didn't notice the alphabet painted on the wall either. From this one could assume that only things that have been in the same place for a long duration 'translate'.

Mas se for esse o caso, então

how would Will know a) that his mother was asking the questions that he subsequently answered with the lights, and b) that the lights/alphabet were there to be interacted with?

Existe algum conjunto de regras para o quanto alguém do Upside-Down pode sentir mudanças mais sutis no mundo normal, seja extrapolado a partir do programa ou dado por aqueles envolvidos com a produção, que explica como qualquer conversa poderia ter aconteceu, do ponto de vista de Will?