Originally Posted by
KorvinStarmast
Given that note taking isn't writing dialogue, the rest of your post is ignored.
Fun fact: jotting down the important bits on a kneeboard while both flying and listening to the controller is something pilots did for many decades: your "science" is not science. (Haven't flown in a while, so I'm not sure if pilots have dumbed themselves down while following the magenta line and stopped using kneeboards, but we are drifting off topic slightly. I spent a lot of years flying and training pilots).
The above noted, yes cognitive overload is a thing - when all channels get filled up errors start to manifest; accident investigations are replete with exampled. However, simply listening to a person and jotting down the important bits is so damned easy even I as a seventh grader (back when dirt was recent) could do it.
Your assertion that people are unable to handle two channels of information flow is suspect.
How the speaker delivers the information (that's on you, GM) informs how hard that information is to process regardless of what else they may, or may not, be doing. Verbal delivery is a learned skill. Reading a three paragraph long box of text to describe the room, for example, is poor technique.
Someone a few posts up mentioned pauses: yeah, do that. It helps the listener digest what's coming in as they engage the audio channel and the "paint a picture in my brain's eye" channel. (and if they are smart, jot down a note or two)