Hack34.Detail and the Limits of Attention


Hack 34. Detail and the Limits of Attention

Focusing on detail is limited by both the construction of the eye and the attention systems of the brain.

What's the finest detail you can see? If you're looking at a computer screen from about 3 meters away, 2 pixels have to be separated by about a millimeter or more for them not to blur into one. That's the highest your eye's resolution goes.

But making out detail in real life isn't just a matter of discerning the difference between 1 and 2 pixels. It's a matter of being able to focus on fine-grain detail among enormously crowded patterns, and that's more to do with the limits of the brain's visual processing than what the eye can do. What you're able to see and what you're able to look at aren't the same.

3.2.1. In Action

Figure 3-1 shows two sets of bars. One set of bars is within the resolution of attention, allowing you to make out details. The other obscures your ability to differentiate particularly well by crowding .1

Figure 3-1. One set of bars is within the resolution of attention (right), the other is too detailed (left)1


Hold this book up and fix your gaze on the cross in the middle of Figure 3-1. To notice the difference, you have to be able to move your focus around without moving your eyesit does come naturally, but it can feel odd doing it deliberately for the first time. Be sure not to shift your eyes at all, and notice that you can count how many bars are on the righthand side easily. Practice moving your attention from bar to bar while keeping your eyes fixed on the cross in the center. It's easy to focus your attention on, for example, the middle bar in that set.

Now, again without removing your gaze from the cross, shift your attention to the bars on the lefthand side. You can easily tell that there are a number of bars therethe basic resolution of your eyes is more than good enough to tell them apart. But can you count them or selectively move your attention from the third to the fourth bar from the left? Most likely not; they're just too crowded.

3.2.2. How It Works

The difference between the two sets of bars is that the one on the left is within the resolution of visual selective attention because it's spread out, while the one on the right is too crowded with detail.

"Attention" in this context doesn't mean the sustained concentration you give (or don't give) the speaker at a lecture. Rather, it's the prioritization of some objects at the expense of others. Capacity for processing is limited in the brain, and attention is the mechanism to allocate it. Or putting it another way, you make out more detail in objects that you're paying attention to than to those you aren't. Selective attention is being able to apply that processing to a particular individual object voluntarily. While it feels as if we should be able to select anything we can see for closer inspection, the diagram with the bars shows that there's a limit on what can be picked out, and the limit is based on how fine the detail is.

We can draw a parallel with the resolution of the eye. In the same way the resolution of the eye is highest in the center [Hack #14] and decreases toward the periphery, it's easier for attention to select and focus on detail in the center of vision than it is further out. Figure 3-2 illustrates this limit.

Figure 3-2. Comparing a pattern within the resolution of attention (left) with one that is too fine (right)


On the left, all the dots are within the resolution required to select any one for individual attention. Fix your gaze on the central cross, and you can move your attention to any dot in the pattern. Notice how the dots have to be larger the further out from the center they are in order to still be made out. Away from the center of your gaze, your ability to select a dot deteriorates, and so the pattern has to be much coarser.

The pattern on the right shows what happens if the pattern isn't that much coarser. The dots are crowded together just a little too much for attention to cope, and if you keep your eyes on the central cross, you can't voluntarily focus your attention on any particular dot any more. (This is similar to the righthand side set of bars in the first diagram, as shown in Figure 3-1.)

Also notice, in Figure 3-2, left, that the dots are closer together at the bottom of the patterns than at the top. They're able to sit tighter because we're better at making out detail in the lower half of visionthe resolution of attention is higher there. Given eye level and below is where all the action takes place, compared to the boring sky in the upper vision field, it makes sense to be optimized that way round. But precisely where this optimization arises in the structure of the brain, and how the limit on attentional resolution in general arises, isn't yet known.

Why is selective attention important, anyway? Attention is used to figure out what to look at next. In the dot pattern on the left, you can select a given dot before you move your eyes, so it's a fast process. But in the other diagram, on the right, moving your eyes to look directly at a dot involves more hunting. It's a hard pattern to examine, and that makes examination a slow process.

3.2.3. In Real Life

Consider attentional resolution when presenting someone with a screen full of information, like a spreadsheet. Does he have to examine each cell laboriously to find his way around it, like the crowded Figure 3-2, right? Or, like the one on the left, is it broken up into large areas, perhaps using color and contrast to make it comprehensible away from the exact center of the gaze and to help the eyes move around?

3.2.4. End Note

  1. Figures reprinted from Trends in Cognitive Sciences, 1(3), He, S., Cavanagh, P., & Intriligator, J., Attentional Resolution, 115-21, Copyright (1997), with permission from Elsevier.



    Mind Hacks. Tips and Tools for Using Your Brain
    Mind Hacks. Tips and Tools for Using Your Brain
    ISBN: 596007795
    EAN: N/A
    Year: 2004
    Pages: 159

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