Cognitive view: information-processing theory (part 1)  (Page 2/4)

Capacity and duration

Although sensory memory can hold quite a lot of information, it cannot keep any of this information for very long due to the constant inflowof new data. Estimates of duration vary somewhat, but most agree that information cannot be kept active in sensory memory for more than afew (e.g., 3-5) seconds.

We cannot possibly process all of the data that sensory memory intakes. Therefore, we must select those sensory data that arerelevant to whatever task we are currently undertaking—and ignore the rest. For the most part, we do this without being very aware ofit.

One bothersome aspect of sensory memory is that it collects some sensory data that we wish we could ignore. Have you ever tried toconcentrate, perhaps on school assignments, but felt distracted by the goings-on around you? That is a classic example of having sensorydata that you felt compelled to process when it didn't meaningfully benefit you.

Imagine Pierre, a student in a busy classroom where a teacher is giving a group of students directions for anassignment. Pierre is trying to concentrate on the teacher's instructions, but some other students are creating a distraction with a butterfly display on the other sideof the room. The problem here, from a cognitive perspective, is that Pierre cannot effectively process both the actions of hisclassmates and the teacher's directions; he must choose whether to pay attention to the distraction or to his teacher. All of thisinformation is contained in sensory memory, but not all of it can be processed in working memory, for reasons we discuss next.

Working memory

Let's clear something up before we get ourselves too involved talking about working memory. Atkinson and Shiffrin originally called thisstore “short-term memory” (to contrast with long-term memory), but modern researchers use the term “working memory” instead. These twoterms have some rather subtle distinctions (which cognitive scholars care deeply about), but for our purposes the differences arenegligible. Thus, in this discussion, we will prefer the more common term “working memory.”

Working memory is where the real business of thinking takes place. This is where your students will process the content of your carefullycrafted lessons as well as your instructions for how to complete their assignments—oh yes, and your warnings regarding proper decorum inthe classroom. This is where rocket scientists do their thing, eventually accomplishing moon landings, sending spacecraft to landwith precision on other planets millions of miles away, and the like. Now you can see that working memory is a space to be respected (pleaseremove your hat, if you are wearing one).

Capacity

The pity is, in spite of all of its capabilities, working memory is a very small place. Well before Atkinson and Shiffrin developed theirinformation-processing model, George Miller (1956) discovered that most individuals have approximately seven cognitive “slots” available to be filled with information at any given timeand that this number varies by about two slots across the population, yielding the now-popular estimate of “seven plus or minus two”elements available in working memory to hold all the information one wishes to cram in.