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Controlled And Automatic Processing

Processing that requires attention uses up limited cognitive (~mental) resources, because short term memory and its input from attention have limited capacity. Short term memory can hold about 7 chunks, so anything that requires conscious processing uses up some of this limited resource. Therefore, if you do two things at the same time that both require conscious, controlled processing, you will do them less well than when you did only one at a time.

For example, when you were learning to drive,(especially if you learned on a stick shift), you had to pay careful attention to everything you did. Steering and operating the pedals (and shifting gears in a manual transmission) all required conscious processing. So did attention to other cars, traffic lights, etc. So sometimes you pressed the wrong pedal or turned the wheel too far, when you were paying attention to a street sign or another car. And having a conversation with someone was both difficult and dangerous, because talking also requires controlled processing.

A task that is very well practiced becomes automatic: Such tasks require little or no mental resources, so that they can be done at the same time as other tasks. They are done quickly and seem automatic, requiring little or no conscious guidance.

For example, now, as an experienced driver, you do many routine driving tasks (like coordinating pedals and steering or, on a stick shift coordinating the clutch and shift lever, as well) quite automatically and unconsciously. You can react to the traffic conditions, and steer and brake because practice has made these reactions more or less automatic. You can carry on a conversation while driving. But when traffic becomes difficult and driving requires more conscious attention, you have less working memory available for conversation (or any other activity).

Controlled and automatic processing can be studied in the laboratory (W. Schneider & R. Shiffrin. Controlled and automatic information processing: I. Psychological Review, 1977, 84, 1-66.) One kind of task is perceptual. Sets of four letters are flashed very rapidly on a computer screen in front of an observer. The observer's task is to detect the presence of target letters which might appear once in the set.

The target letters were chosen in one of two ways. Under one condition, the target letters changed after about 100 sets of letters. Because the observer had to keep changing which letters to look for, this task required conscious attention throughout testing and therefore used controlled processing. If a second task requiring controlled processing was done at the same time, performance on both declined.

In the second general condition for this task, the target letters remained the same throughout testing, which lasted for several thousand trials. Because the target letters remained the same, processing eventually became automatic. detecting the target became much faster, and observers reported that the target seemed to jump out from among the other letters.

Performance on this task became much better than on the controlled processing task. Furthermore, when observers did the controlled task and the automatic task at the same time, their performance was not affected. This shows that the automatically processed task requires little or no working memory or conscious attention.