Source: Wikimedia Commons

When you open your eyes, you see (in your mind's eye) a picture of the world around you. Even though the image looks fairly stable, your eyes are constantly in motion. There is a small area of densely-packed cells at the back of the retina in your eye called the fovea that is source of your best vision. The area of this high-quality vision is about the size of your thumbnail if you hold your arm straight out. In order to really see well, you have to aim your fovea at different objects in the world and build up a sense of what there is in the world around you.

Psychologists have explored many factors that influence what you point your eyes at when looking at a scene. People tend to look at information that will help them achieve their , for example. They also look at items in that are important to them like human faces.

An important question about vision is whether these eye movements are directed primarily toward specific aspects of the scene or whether they are driven by conceptual knowledge about what to expect to see in the environment. This question was explored in a paper in the April, 2015 issue of the Journal of Experimental Psychology: General by Alayton Hickey, Daniel Kaiser, and Marius Peelen.

They showed people pictures of real-world scenes containing objects like trees, people, and cars. On each trial, participants saw a picture and had to search for a particular object (like a person) and press one button if the picture had that object in it and a second button if it did not. The target people were supposed to find changed from trial to trial. Importantly, each picture showed different people, trees, and cars.

The researchers were most interested in whether searching for a particular object in one picture influenced your speed and accuracy for the next picture. Suppose, you search for a person in a picture. On the next picture, you are told to find a car. The question is whether you are slower and less accurate in your response if there is also a person in that picture. If so, that would suggest that the reward you got for getting a correct answer on the previous picture persists in affecting your to the next picture.

In fact, that is what happens. When the target you were supposed to find in the previous picture occurs again in a picture in which it is not the target, that slows you down and makes you a little less accurate in responding. At first, that doesn’t seem so surprising. But, remember that the pictures are all natural scenes. So, the people, cars, and trees in these scenes are all different. That means that your visual system is not searching for very specific features to help it find a target. Instead, it is looking for the kinds of properties that generally signal that something is a tree, car, or person.

To demonstrate this point more strongly, in one final study, many of the objects were partially occluded. That is, part of the object was hidden. For example, a person might be walking behind a garbage can, so that only their torso and head are visible. In another picture, a person might be standing behind a sign, so that you can see their hips and legs, but not their torso and head.

As in the previous studies, people would often search for a target in one picture and an object of the same type appeared in the next picture but was not the target. This time, though, the features of the object that were visible when it was the target were different from those visible when it was a distractor. For example, people might see the head and torso when search for a person and then see the legs and hips of a person when searching for a car in the subsequent picture.

Once again, people were slower and less accurate when the target from a previous picture showed up as a distractor on the next trial (compared to pictures where the previous target was not present). Because there are completely different features available in the pictures from one to the next, this result suggests that visual attention is being driven by the category of the target and not by specific visual features of that target.

For example, different cars share some features, but they can be quite dissimilar. They can vary in many ways including size, shape, color, whether they are being seen from the side or head-on. Yet, when you go searching for a member of a particular category, your visual system is prepared to see all of these kinds of properties and not just specific features that were available recently in the visual environment.

So, this simple experimental finding reflects a complex interplay between vision and our conceptual abilities.

Follow me on Twitter.

And on Facebook and on Google+.

Check out my new book Smart Change.

And my books Smart Thinking and Habits of Leadership

Listen to my radio show on KUT radio in Austin Two Guys on Your Head and follow 2GoYH on Twitter and on Facebook.