This is because it is easier to create such images in sufficiently large numbers (imagine having to find thousands of real-world images of camouflaged snipers), and because this makes visual search simpler, which in turn makes it easier to study visual search in the laboratory. How does the brain find what it is looking for, and how do researchers go about understanding how the brain does this? For one thing, researchers often use simplified, computer-generated visual “scenes” ( Figures 1C–E). So, you can clearly see that visual search is a very important part of how the brain works in real life. On the other hand, a predator may starve to death if it is not good enough at finding its prey, or if its prey finds it too easily. In the wild, animals must spot potential predators quickly enough to flee to safety. Disaster can strike if smart machines, such as driverless cars or medical diagnostic equipment, fail to find the targets they are designed to find. Similarly, military specialists undergo extensive training to find enemy snipers or landmines camouflaged against the background. Doctors train for years to become good at finding cancers in breast X-rays ( Figure 1B) or chest X-rays, for example. Sometimes, finding a target takes special training and can be a matter of life or death. (F) The graph shows how reaction times for locating a target change depending on the number of distractors in the image and whether the target pops out or not. (E) Under certain circumstances, including most real-world scenes, the target does not pop out, because it shares some characteristics of the other objects in the scene (see arrow in Figure 3E). (D) A pop-out scene in which the odd-man-out, the horizontal red bar, is easily found (see arrow in Figure 3D). (C) Can you find the human head camouflaged against the background? (For the answer, see Figure 3C). It takes considerable medical training and experience to learn to detect such cancers. The cancerous region is much subtler (see arrow in Figure 3B). While the bright parts of the image toward the front of the breast tend to attract our attention, they are not cancerous. (B) An x-ray image of a breast with cancer. Can you find the peanut? (For the answer, see arrow in Figure 3A). Figure 1 - Visual scenes with multiple objects always require visual search.These activities are fun, because they make a game out of what we do in real life all the time-that is, look for an object of interest, or a “target,” among distracting things that we do not want, or “distractors.” These games let us experience the sweet frustration of looking for a target and not finding it, or the joy of finding it. Older people-such those in their thirties and forties-may remember “Where’s Waldo?” a popular game found in comic books of their day. Many of us remember passing time on long, dreary road trips by playing “I SPY” ( Figure 1A) or “Airport Scanner” on our cell phones or tablets. Visual Search Is a Fact of Life, and Can Be a Matter of Life or Death While much remains to be discovered, what we have learned so far offers a fascinating window into how we see. Understanding how we search for, and find, objects we are looking for is crucial to understanding how ordinary people and experts alike operate in the real world. But, in some cases, it takes special training to find things, such as when searching for cancers in X-rays, weapons or explosives in airport luggage, or an enemy sniper hidden in the bushes. We perform visual search all the time in everyday life, because the objects we want are almost always surrounded by many other objects. This process of looking for an object of interest is called visual search. We have all have experienced the frustration of looking for something we want, only to find a seemingly endless series of things we do not want.
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