When I first start to become overloaded, my attention feels spread thin and I have a hard time processing information and staying on task. With auditory information, I can't help but concentrate on all the noises around me, visualizing their source and placing them spatially in my mind. With visual information, things become blurred and my response is to stare at the ground until (and if) I can adapt to the barrage of colors, details, and motion in front of me. This is my typical response to any kind of stimulation, but I can usually prevent it from progressing past this stage.
If my methods of coping don't help deescalate the problem, though, I begin to react emotionally and become irritable and withdrawn. I don't think people notice, as I don't tend to express emotion on these occasions. My ability to process information will also decrease exponentially and eventually everything will be dark and quiet. That's when I enter "shutdown mode" and it becomes difficult to speak, move, and think.
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I have not the kind affections of a pigeon. - Ralph Waldo Emerson