Roll After Dark

Blindfolds, sensory deprivation

Sight, hearing, or both taken away with a covering, plugs, or a hood.

Why people do it
Take sight away and everything else gets louder — a fingertip becomes an event. It also removes the social self-consciousness that stops a lot of people relaxing, because nobody is being looked at any more.
Smallest way in
A folded scarf over the eyes for ten minutes while you do something perfectly ordinary to them. That is the entire experiment, and it usually settles the question.
What to watch
If hearing goes too, speech is no longer a channel and you need a physical one — two squeezes out, two squeezes back, every visit. Never combine full deprivation with being left alone.
In the planner
10 different things carry this tag, and switching it off removes every one of them. The mildest of them sits at easy.