24-3 How do explicit and implicit memories differ?

Atkinson and Shiffrin’s model focused on how we process our explicit memories—the facts and experiences that we can consciously know and declare (thus, also called declarative memories). But our mind has a second, unconscious track. We encode explicit memories through conscious effortful processing. Behind the scenes, other information skips the conscious encoding track and barges directly into storage. This automatic processing, which happens without our awareness, produces implicit memories (also called nondeclarative memories).

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24-4 What information do we process automatically?

Our implicit memories include procedural memory for automatic skills (such as how to ride a bike) and classically conditioned associations among stimuli. If attacked by a dog in childhood, years later you may, without recalling the conditioned association, automatically tense up as a dog approaches.

Without conscious effort you also automatically process information about

Our two-track mind engages in impressively efficient information processing. As one track automatically tucks away many routine details, the other track is free to focus on conscious, effortful processing. Mental feats such as vision, thinking, and memory may seem to be single abilities, but they are not. Rather, we split information into different components for separate and simultaneous parallel processing.

Automatic processing happens effortlessly. When you see words in your native language, perhaps on the side of a delivery truck, you can’t help but read them and register their meaning. Learning to read wasn’t automatic. You may recall working hard to pick out letters and connect them to certain sounds. But with experience and practice, your reading became automatic. Imagine now learning to read reversed sentences like this:

     .citamotua emoceb nac gnissecorp luftroffE

At first, this requires effort, but after enough practice, you would also perform this task much more automatically. We develop many skills in this way: driving, texting, and speaking a new language.

Sensory Memory

24-5 How does sensory memory work?

Sensory memory (recall Figure 24.3) feeds our active working memory, recording momentary images of scenes or echoes of sounds. How much of this page could you sense and recall with less exposure than a lightning flash? In one experiment, people viewed three rows of three letters each, for only one-twentieth of a second (FIGURE 24.5). After the nine letters disappeared, they could recall only about half of them.

Was it because they had insufficient time to glimpse them? No. George Sperling cleverly demonstrated that people actually could see and recall all the letters, but only momentarily. Rather than ask them to recall all nine letters at once, he sounded a high, medium, or low tone immediately after flashing the nine letters. This tone directed participants to report only the letters of the top, middle, or bottom row, respectively. Now they rarely missed a letter, showing that all nine letters were momentarily available for recall.

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Sperling’s experiment demonstrated iconic memory, a fleeting sensory memory of visual stimuli. For a few tenths of a second, our eyes register a photographic or picture-image memory of a scene, and we can recall any part of it in amazing detail. But if Sperling delayed the tone signal by more than half a second, the image faded and participants again recalled only about half the letters. Our visual screen clears quickly, as new images are superimposed over old ones.

We also have an impeccable, though fleeting, memory for auditory stimuli, called echoic memory (Cowan, 1988; Lu et al., 1992). Picture yourself in conversation, as your attention veers to your smartphone screen. If your mildly irked companion tests you by asking, “What did I just say?” you can recover the last few words from your mind’s echo chamber. Auditory echoes tend to linger for 3 or 4 seconds.

Capacity of Short-Term and Working Memory

24-6 What is the capacity of our short-term and working memory?

Recall that working memory is an active stage, where our brains make sense of incoming information and link it with stored memories. What are the limits of what we can hold in this middle stage?

George Miller (1956) proposed that we can store about seven bits of information (give or take two) in short-term memory. Miller’s magical number seven is psychology’s contribution to the list of magical sevens—the seven wonders of the world, the seven seas, the seven deadly sins, the seven primary colors, the seven musical scale notes, the seven days of the week—seven magical sevens.

Other researchers have confirmed that we can, if nothing distracts us, recall about seven digits, or about six letters or five words (Baddeley et al., 1975). How quickly do our short-term memories disappear? To find out, Lloyd Peterson and Margaret Peterson (1959) asked people to remember three-consonant groups, such as CHJ. To prevent rehearsal, the researchers asked them, for example, to start at 100 and count aloud backward by threes. After 3 seconds, people recalled the letters only about half the time; after 12 seconds, they seldom recalled them at all (FIGURE 24.6). Without the active processing that we now understand to be a part of our working memory, short-term memories have a limited life.

Working memory capacity varies, depending on age and other factors. Compared with children and older adults, young adults have more working memory capacity, so they can use their mental workspace more efficiently. This means their ability to multitask is relatively greater. But whatever our age, we do better and more efficient work when focused, without distractions, on one task at a time. The bottom line: It’s probably a bad idea to try to watch TV, text your friends, and write a psychology paper all at the same time (Willingham, 2010)!

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Unlike short-term memory capacity, working memory capacity appears to reflect intelligence level (Cowan, 2008; Shelton et al., 2010). Imagine seeing a letter of the alphabet, then a simple question, then another letter, followed by another question, and so on. In such experiments, those who could juggle the most mental balls—who could remember the most letters despite the interruptions—tended in everyday life to exhibit high intelligence and an ability to maintain their focus (Kane et al., 2007; Unsworth & Engle, 2007). When beeped to report in at various times, they were less likely than others to report that their mind was wandering. Those with a large working memory capacity—whose minds can juggle multiple items while processing information—tend also to retain more information after sleep and to be creative problem solvers (De Dreu et al., 2012; Fenn & Hambrick, 2012; Wiley & Jarosz, 2012).

Effortful Processing Strategies

24-7 What are some effortful processing strategies that can help us remember new information?

Several effortful processing strategies can boost our ability to form new memories. Later, when we try to retrieve a memory, these strategies can make the difference between success and failure.

CHUNKING Glance for a few seconds at the first set of letters in FIGURE 24.7, then look away and try to reproduce what you saw. Impossible, yes? But you can easily reproduce set 2, which is no less complex. Similarly, you will probably remember sets 4 and 6 more easily than the same elements in sets 3 and 5. As this demonstrates, chunking information—organizing items into familiar, manageable units—enables us to recall it more easily. Try remembering 43 individual numbers and letters. It would be impossible, unless chunked into, say, seven meaningful chunks, such as “Try remembering 43 individual numbers and letters.”

Chunking usually occurs so naturally that we take it for granted. If you are a native English speaker, you can reproduce perfectly the 150 or so line segments that make up the words in the three phrases of set 6 in Figure 24.7. It would astonish someone unfamiliar with the language. I am similarly awed at a Chinese reader’s ability to glance at FIGURE 24.8 and then reproduce all the strokes; or of a varsity basketball player’s recall of the positions of the players after a 4-second glance at a basketball play (Allard & Burnett, 1985). We all remember information best when we can organize it into personally meaningful arrangements.

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MNEMONICS To help them encode lengthy passages and speeches, ancient Greek scholars and orators developed mnemonics. Many of these memory aids use vivid imagery, because we are particularly good at remembering mental pictures. We more easily remember concrete, visualizable words than we do abstract words. (When we quiz you later, which three of these words—bicycle, void, cigarette, inherent, fire, process—will you most likely recall?) If you still recall the rock-throwing rioter sentence, it is probably not only because of the meaning you encoded but also because the sentence painted a mental image.

The peg-word system harnesses our superior visual imagery skill. This mnemonic requires you to memorize a jingle: “One is a bun; two is a shoe; three is a tree; four is a door; five is a hive; six is sticks; seven is heaven; eight is a gate; nine is swine; ten is a hen.” Without much effort, you will soon be able to count by peg words instead of numbers: bun, shoe, tree … and then to visually associate the peg words with to-be-remembered items. Now you are ready to challenge anyone to give you a grocery list to remember. Carrots? Stick them into the imaginary bun. Milk? Fill the shoe with it. Paper towels? Drape them over the tree branch. Think bun, shoe, tree and you see their associated images: carrots, milk, paper towels. With few errors, you will be able to recall the items in any order and to name any given item (Bugelski et al., 1968). Memory whizzes understand the power of such systems. A study of star performers in the World Memory Championships showed them not to have exceptional intelligence, but rather to be superior at using mnemonic strategies (Maguire et al., 2003).

When combined, chunking and mnemonic techniques can be great memory aids for unfamiliar material. Want to remember the colors of the rainbow in order of wavelength? Think of the mnemonic ROY G. BIV (red, orange, yellow, green, blue, indigo, violet). Need to recall the names of North America’s five Great Lakes? Just remember HOMES (Huron, Ontario, Michigan, Erie, Superior). In each case, we chunk information into a more familiar form by creating a word (called an acronym) from the first letters of the to-be-remembered items.

HIERARCHIES When people develop expertise in an area, they process information not only in chunks but also in hierarchies composed of a few broad concepts divided and subdivided into narrower concepts and facts. (Figure 25.4 in the next module provides a hierarchy of our automatic and effortful memory processing systems.) Organizing knowledge in hierarchies helps us retrieve information efficiently, as Gordon Bower and his colleagues (1969) demonstrated by presenting words either randomly or grouped into categories. When the words were grouped, recall was two to three times better. Such results show the benefits of organizing what you study—of giving special attention to module headings, numbered Learning Objective questions, Retrieval Practice questions, module reviews, and the Test Yourself questions. Taking lecture and text notes in outline format—a type of hierarchical organization—may also prove helpful.

Distributed PracticeWe retain information better when our encoding is distributed over time. More than 300 experiments over the past century have consistently revealed the benefits of this spacing effect (Cepeda et al., 2006). Massed practice (cramming) can produce speedy short-term learning and a feeling of confidence. But to paraphrase early memory researcher Hermann Ebbinghaus (1885), those who learn quickly also forget quickly. Distributed practice produces better long-term recall. After you’ve studied long enough to master the material, further study at that time becomes inefficient. Better to spend that extra reviewing time later—a day later if you need to remember something 10 days hence, or a month later if you need to remember something 6 months hence (Cepeda et al., 2008). The spacing effect is one of psychology’s most reliable findings, and it extends to motor skills and online game performance, too (Stafford & Dewar, 2014). Memory researcher Henry Roediger (2013) sums it up: “Hundreds of studies have shown that distributed practice leads to more durable learning.”

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Distributing your learning over several months, rather than over a shorter term, can even help you retain information for a lifetime. In a 9-year experiment, Harry Bahrick and three family members (1993) practiced foreign language word translations for a given number of times, at intervals ranging from 14 to 56 days. Their consistent finding: The longer the space between practice sessions, the better their retention up to 5 years later.

One effective way to distribute practice is repeated self-testing, a phenomenon that researchers Roediger and Jeffrey Karpicke (2006) have called the testing effect. Testing does more than assess learning: It improves it (Karpicke, 2012; McDaniel, 2012). In this text, for example, the Retrieval Practice and Test Yourself questions offer such an opportunity. Better to practice retrieval (as any exam will demand) than merely to reread material (which may lull you into a false sense of mastery). Roediger (2013) explains, “Two techniques that students frequently report using for studying—highlighting (or underlining) text and rereading text—[have been found] ineffective.” Happily, “retrieval practice (or testing) is [a] powerful and general strategy for learning.” As another memory expert explained, “What we recall becomes more recallable” (Bjork, 2011).

The point to remember: Spaced study and self-assessment beat cramming and rereading. Practice may not make perfect, but smart practice—occasional rehearsal with self-testing—makes for lasting memories.

Levels of Processing

24-8 What are the levels of processing, and how do they affect encoding?

Memory researchers have discovered that we process verbal information at different levels, and that depth of processing affects our long-term retention. Shallow processing encodes on a very basic level, such as a word’s letters or, at a more intermediate level, a word’s sound. Deep processing encodes semantically, based on the meaning of the words. The deeper (more meaningful) the processing, the better our retention.

In one classic experiment, researchers Fergus Craik and Endel Tulving (1975) flashed words at people. Then they asked questions that would elicit different levels of processing. To experience the task yourself, rapidly answer the following sample questions:

Which type of processing would best prepare you to recognize the words at a later time? In Craik and Tulving’s experiment, the deeper, semantic processing triggered by the third question yielded a much better memory than did the shallower processing elicited by the second question or the very shallow processing elicited by the first question (which was especially ineffective).

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Making Material Personally MeaningfulIf new information is not meaningful or related to our experience, we have trouble processing it. Put yourself in the place of the students who were asked to remember the following recorded passage:

The procedure is actually quite simple. First you arrange things into different groups. Of course, one pile may be sufficient depending on how much there is to do…. After the procedure is completed, one arranges the materials into different groups again. Then they can be put into their appropriate places. Eventually they will be used once more and the whole cycle will then have to be repeated. However, that is part of life.

When the students heard the paragraph you have just read, without a meaningful context, they remembered little of it (Bransford & Johnson, 1972). When told the paragraph described washing clothes (something meaningful), they remembered much more of it—as you probably could now after rereading it.

Can you repeat the sentence about the rioter that we gave you at this module’s beginning? (“The angry rioter threw . . .”)?

Perhaps, like those in an experiment by William Brewer (1977), you recalled the sentence by the meaning you encoded when you read it (for example, “The angry rioter threw the rock through the window”) and not as it was written (“The angry rioter threw the rock at the window”). Referring to such mental mismatches, some researchers have likened our minds to theater directors who, given a raw script, imagine the finished stage production (Bower & Morrow, 1990). Asked later what we heard or read, we recall not the literal text but what we encoded. Thus, studying for an exam, you may remember your lecture notes rather than the lecture itself.

We can avoid some of these mismatches by rephrasing information into meaningful terms. From his experiments on himself, Ebbinghaus estimated that, compared with learning nonsense material, learning meaningful material required one-tenth the effort. As memory researcher Wayne Wickelgren (1977, p. 346) noted, “The time you spend thinking about material you are reading and relating it to previously stored material is about the most useful thing you can do in learning any new subject matter.”

Psychologist-actor team Helga Noice and Tony Noice (2006) have described how actors inject meaning into the daunting task of learning “all those lines.” They do it by first coming to understand the flow of meaning: “One actor divided a half-page of dialogue into three [intentions]: ‘to flatter,’ ‘to draw him out,’ and ‘to allay his fears’.” With this meaningful sequence in mind, the actor more easily remembers the lines.

We have especially good recall for information we can meaningfully relate to ourselves. Asked how well certain adjectives describe someone else, we often forget them; asked how well the adjectives describe us, we remember the words well. This tendency, called the self-reference effect, is especially strong in members of individualist Western cultures (Symons & Johnson, 1997; Wagar & Cohen, 2003). Information deemed “relevant to me” is processed more deeply and remains more accessible. Knowing this, you can profit from taking time to find personal meaning in what you are studying.

The point to remember: The amount remembered depends both on the time spent learning and on your making it meaningful for deep processing.