Our eyes inherently move in quick sputters with small periods of stillness back and forth. These sputters/jumps are called saccades, which move forward the majority of the time but also move backward 10-15% of the time while reading.

During this time, a person is essentially blind, but the transitions of saccades to fixations are so fast we don’t notice.

We use peripheral vision when we read, and because of this, a saccade can view up to 15 letters, but we do often go back and reread those letters. We only get meaning out of 7-9 of those 15 letters at a time.

The moments of stillness are called fixations, they last about 250 milliseconds and are the only real time we can see and focus on the words.