According to this book: https://valsec.barnesandnoble.com/w/slow-down-time-the-power... , it basically happens because the number of snapshots you encode per second goes down. Snapshots are visual cues that we encode. The best example is that if we are watching a fan start, after a certain speed, we cannot tell how many wings are there on the fan. We are not snapshotting fast enough. Younger people can probably tell the number of wings on a faster fan :). Various things slow down this snapshotting in our brain, and the best antidote is to get in the zone and do things with immense attention.