Part of what is happening I think is that visual perception is mostly constructed, rather than being a simple reflection of stimuli in front of us. David Eagleman accessibly discusses a number of lines of evidence for this surprising conclusion in Incognito. This probably has a lot to do with the oddities of perception and imagination that happen when we engage in sensory deprivation of various kinds.

The “adaptation” effects seem to be related to that as well. The perceptual mechanisms seem optimized to make us aware of changes and things that the brain predicts might require action, rather than just giving an unbiased capture of everything in front of us.

This is a very big deal conceptually, and I suspect most people probably reject the idea when they first consider it because it seems so different than they way we naturally think of perception. There are a lot of different lines of evidence leading to the same odd counter-intuitive conclusion though.

after some time either during a meditation or after a period of regular practice the stillness becomes very profound. it is not a tuning out because you have trained yourself to stay with. daily life becomes more present in your experience.

scientists have noticed various neurological patterns when observing meditators and non meditators, and over time a thickening of the insula. this has to be connected to a trained lack of distraction.