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We already know that attention is a limited resource, and we can't focus on everything in our environment at once. But how do we filter out the unimportant information, and how do we decide when to shift our attention to something new? You've probably experienced that even when you're in a loud crowded room, you're pretty good at attending to the one person who's talking to you. But you still hear bits and pieces of conversations that you're not trying to attend to. What those bits and pieces are and aren't are what interest psychologists who study selective attention, or your ability to focus on something that's relevant to the task at hand while ignoring other information. One way to study selective attention is to observe people while they're doing something called a shadowing task. In this task, you're wearing a pair of headphones, but different information is coming in through each ear piece. So through the left ear, you're hearing one thing, and through the right ear, you're hearing something completely different, maybe a different person's voice, maybe a different language, even. And you're told to repeat everything that's said into one ear, say, your right ear, so you have to pay attention to it and to ignore the other. Based on what we learn about the type of unattended information that we actually do and don't end up comprehending, we can then learn more about how selective attention works. And there are three major theories that try to explain this process. I'm going to talk about these theories in terms of auditory attention, but the same idea applies to other senses as well. The first is Broadbent's early selection theory. Broadbent's idea was that all the information in your environment goes into your sensory register, which briefly registers or stores all the sensory input you get. This includes words, clicks, sirens, any input at all. Then this input gets transferred to the selective filter right away, which identifies what it's supposed to be attending to via basic physical characteristics. So if we're talking about language, the selective filter identifies the voice, pitch, speed, accent, basic things like that, that you don't really need to understand in order to identify. Everything else gets filtered out, and the selected information gets moved along so that perceptual processes can occur. These processes assign meaning to the information. So while the selective filter identifies the pitch of the one you want to pay attention to, the perceptual processes identify it as your friend's voice and assign meaning to the words. Then you can engage in other cognitive processes, such as deciding how to respond. Broadbent's theory was a good start, but there are some problems. If you completely filter out the unattended information before it gets assigned meaning, then you shouldn't be able to identify your own name when it's spoken in an unattended ear. But as you've probably experienced, you immediately perk up when you hear your own name, even when it's across the room and you haven't been paying attention to that conversation before. This is known as the cocktail party effect, and this, among other things, led to researchers coming up with a new theory. A couple folks named Deutsch & Deutsch proposed a late selection theory, which moved Broadbent's selective filter to after the perceptual processes. This means that you actually do register and assign everything meaning, but then your selective filter decides what to pass on to your conscious awareness. That sounds pretty good, but keep in mind that all this has to happen really quickly. Given the limited resource of attention, and the fact that we know our brains are super-efficient, it seems a little wasteful to spend all that effort assigning meaning to stuff you won't ever need. So the answer may be somewhere in between early selection and late selection. So we come to Treisman's attenuation theory of selective attention. Treisman said that instead of a complete filter, we have something called an attenuator. Attenuate just means to weaken. So the attenuator weakens but doesn't eliminate the input from the unattended ear. Then some of it gets through to the perceptual processes. So we still assign meaning to stuff in the unattended ear. It's just not as high priority. At this point, if you realize that the unattended stuff is actually important, then you'll switch over your attention and attenuate what you were previously listening to. Later experiments suggested that the difficulty of the task you're attending to can affect when filtering occurs and how long it takes. The bottom line is there's still some debate about which theory is the absolute best. But these three theories have been pivotal in our understanding of selective attention. It's important to consider because attention is crucial to any other cognitive function we perform. If infants weren't able to attend a human voices and filter out birds chirping or dogs barking, it'd be nearly impossible to learn to speak. And if we didn't have some way to refocus on to unattended information, then we'd never notice if a car was coming straight for us or if someone yelled fire. So now, hopefully, you have a little better understanding of the theories that try to explain this important process.