Chapter 4 Overt and covert attention

Human brains have a bottleneck problem. But our ancestors many millions of years ago didn’t! When our senses first started to evolve in simpler animals, they didn’t have the high processing capacity they have today. For instance, the first organism to have vision may have had only one photoreceptor. So, later processing stages were not overwhelmed!

However, primitive animals still had one kind of attention. For an object in the environment to be processed, an animal had to point its photoreceptor at it so the light from that object would stimulate its photoreceptor.

When an animal moves its sensory apparatus to better process something, we call that overt attention.

4.1 Two reasons for overt attention

Animals like us have millions of photoreceptors, but we still have a limited field of view. Therefore, we move our head and eyes around a lot in order to get objects of interest in our field of view. Again, this is called overt attention.

But getting the object in our field of view is not the only reason we move our eyes. Just as often, we move our eyes because we need to look directly at something to see it well.

Peripheral vision, away from the center of where you’re looking, is low resolution. Many people either don’t know this or don’t fully appreciate just how bad peripheral vision is. That’s because people move their eyes to an object as soon as they’re interested in it, so they never notice that their vision of it wasn’t good to begin with.

4.2 Peripheral vision

To get some feel for the poor quality of peripheral vision, try reading the text in the red and green squares when you have your eyes on the black dot in the center. Researchers refer to keeping one’s eyes fixed on a point fixating. So, we call the black dot the fixation point.

Figure 4.1: Peripheral vision has poor spatial resolution, which is why when one is looking directly at the black dot, one can’t read the text in the colored boxes

When you fixate on the fixation point, you can’t read the words because outside of the centre of vision, the signals passed onto your brain are low resolution, like an image with not enough pixels.

So, overt attention is not just about moving your eyes and head so that you can see it, it’s also about making sure there’s a chance to perceive the object very well, by pointing your eyes directly at it, or at least very near it.

4.3 Covert attention

Covert attention refers to action to process part of the world more by using your mind rather than by your eyes or head. Try staring at the black dot below, and attending to different letters without moving your eyes.

Unlike in the previous display, in this display the letters are probably big enough for you to read even when you are fixating (staring at) the black dot at the center.

You’re able to choose to concentrate on an individual letter, like ‘H’. Or you can concentrate on two letters, like the ‘E’ and the ‘D’. Try it!

Scientists refer to this as attending to those letters. When you do it, your mind processes those letters more than the other letters. This is the phenomenon of covert attention.

A previous chapter (3) explained that we have bottlenecks in the brain. It’s because of them that we need covert attention. When there’s a lot of stimulation on our retinas, if there’s anything important, we need to attend to them to be sure that those get through the bottleneck into higher-level processes.

4.4 Exercises

Answer these questions and relate them to the learning outcomes ( 2 ):

  • Explain the difference between covert attention and overt attention.
  • What was the first display of this chapter used to illustrate?
  • What are two reasons for overt attention?
  • What was the second display of this chapter used to illustrate?