I have done many months of research on this topic, for it interests me very much. What I have found in my clinical experiments is that you needn't clinical research, just the ability to remove oneself from the computer screen for twenty seconds.
Try taking a few sips of water. Wait a few moments. Need more nourishment? Eat some fruit.
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For me it's when my throat is dry and/or my teeth clench together (I have no idea why that happens to me).