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It can be a very good practice (and a quick way to attain a trance state) to pay some attention to these attentional artefacts when they show up.
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That's not something I've noticed explicitly, though vision sort of doing small weird things (going in and out of focus), for sure. The first one I remember clearly is hearing a sort of very faint, octavated, hilariously squeaky version of my voice in my ear every time I spoke.
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