I was sitting beside my friend and I asked myself a question out loud which required scanning a mapped list (numbers-names) to find the answer. She heard and tried to help. I looked at her eyes while trying to find the answer myself and suddenly her eyes moved very quickly from center to right in a jerky manner (and back again). It lasted for about half a second. She regained focus at me and spelled out the answer. During those quick movements (from center to right and back again) I realized her eyes were not focused on anything. It was as if she was scanning her own brain with her eyes. I assume they were involuntary movements. I strongly doubt a human can move their eyes' muscles so quickly consciously. The movement loop was simply too fast. Are there any biological explanations as to what may have happened? Any neurological explanation, or this may actually be quite the complex process to be addressed with a simple answer? Thanks.