Have you ever had the experience of just minding your own business, when suddenly something in the corner of your eyes catches your attention? What’s that about?

This is something universal amongst many animals that have separate brain hemispheres. Imagine a bird sitting in a tree eating an apple, when it suddenly spots a buzzard approaching in the corner of its eyes, which alerts it to hide. The bird was paying direct attention to the apple it was eating, but at the same time a separate attention was working to spot any potential predators outside of its direct focus. You can see why this has an evolutionary advantage.

In humans this works the same way, we can focus on the task at hand, but if we spot something in the corners of our eyes we can rapidly change our focus to that point. These are two different types of attention at work.

What are the properties of these two types of attention? Most of us are the most familiar with the first type of attention, direct focus. We work on something, like washing our hands, and see our own hands moving around. We focus on the task. This attention magnifies whatever the current task is, and doesn’t take into account whatever is outside of it. Like a lens, this attention only sees whatever is in focus: the current task.

The second type of attention is a bit different. Usually it goes unnoticed, because it often works more outside of our consciousness, but not necessarily. This type of attention sees the things that are out of focus: whatever’s outside of the current task. It sees the blurry corners of our eyes, and can signal us whenever something interesting happens, so we can point our direct attention at it and see it clearer.

I like to give these types of attention a name. Let’s call the direct type of attention the depth attention, and the more vague type of attention the breadth attention. One of them focuses and can see the details, but can not see whatever’s outside of focus, and the other sees whatever’s outside of focus, but not what is in focus. These two are exclusive.

A proper analogy would be a microscope. Imagine you have a book. At first you can see it by itself and with its surrounding objects, but the only thing you can see are the objects themselves. Now you pick out the book and look at a page under a microscope. Zoom in, and you see each letter by itself. Zoom even further, and you will see every individual fiber the paper is made out of. If you would look at the zoomed in image, you wouldn’t even know that you are looking at a book, but look at the book outside of the microscope, and you wouldn’t even know that the paper of the book is made out of individual fibers if you hadn’t looked at a page under the microscope. Breadth and depth are mutually exclusive, which warrant the two types of attention. You can not have both at the same time.

To solve this mutual exclusion, your brain is divided into two hemispheres, each being in charge of one of the two types of attention, and they share information with each other to work together. Your left hemisphere is in charge of the depth attention, and your right hemisphere is in charge of the breadth attention.

This is far from the only differences between the two hemispheres, but this difference is one part of the general pattern that exists between the relationship of the two hemispheres, and in the way knowledge works. Expect more posts about these differences.

A useful analogy is that the two hemispheres work together like CPU cores do in a computer. They can both work on their own tasks, but they can also share information with each other. They function relatively independent from one another, but have access to information from the other, and need it to work properly.