Most of us never give any thought to how we see.  We just look at something, and there it is.  Clear as a bell.

Quickly look left or right and there is no blur.

One of the things interesting about this phenomenon of everything staying in focus is that while we perceive that our vision is very controlled and directional, the eye is constantly moving.  The purpose for this type of involuntary, coordinated, rapid eye movement (saccade) allows us to build a three dimensional map that represents what we are seeing.  When whatever we are looking at expands past 20° of view, our heads move slightly to keep the field of view continuous.  Our brains appear to hold on to an image for about 1/15 of a second.  If something occurs in our visual field during that time – like rapidly flipping through still pictures – we perceive a sense of continuous motion.  Involuntary rapid eye movements are controlled at two levels of our brain: cortically and subcortically.  The double connection helps us understand and see faster.

Major point #1 – You can only focus on one thing at a time – visually.

When we look at something, the center area of view is in focus with the rest of the visual field somewhat out of focus.  The following pictures illustrate how the eye focuses.  Start with the cake in the center of this picture.

When you look at the cake, it is in focus and the rest is slightly out of focus, or blurred. In the next picture, the focus is on the plate on the left.

As you move your gaze from the cake to the plate, the cake blurs and the plate is sharp.

Moving on to the glass in the upper right corner continues the pattern of new focus and blur

We see without being aware of what is going on because the:

  • time lapse is short,
  • optic nerve connects to two parts of the brain,
  • eyes rapidly move in a coordinated way.

In an earlier post on selective attention, I linked to a video – The Monkey Business Illusion – where the viewer is asked to count the number of ball passes made between team members.  I have shown this to a number of groups, and the viewers who focus on the passes and do not think about anything else, arrive at the right number.  There were also viewers who thought that someone on the other team was going to do something, so they tried to watch for that while counting.  None of these viewers counted the correct number of passes.

Every viewer to a person missed the forest for the trees.  If you have not seen the video, go look.  I have given you a hint – the other team plays by the rules, so that should not be a distraction.

Two things are going on in the video related to what people observe.  First, if visually focusing on the ball, the background is blurred.

The second component is an intellectual one.  The directions for the video tell the viewer to focus on certain parameters.  When processing the information presented, the viewer “blurs out” information not pertinent to the task.

 Due to the directions, the viewer’s intellectual focus is restricted more than normal as well.

Major point #2 – You can only focus on one thing at a time – intellectually.

Which leads me to the following conclusion:

Major point #3 – It is not possible to multi-task.  At best, you can rapidly serial task.

We can only focus on one thought, idea, or problem at a time.  When we think of something else, we move our intellectual focus to that, with the previous thought slightly blurred.  If those thoughts occur closely enough to each other in time, we perceive that they are occurring simultaneously.

Rapidly serial tasking can be distracting when trying to accomplish something, like trying to count passes or taking in your environment.  It also explains why people misunderstand what others are saying to them when the listener is “multitasking”.