Wednesday, February 22, 2017

Sleep Needed for Memory

Got kids or grandkids in school? Odds are they are not getting enough sleep, and it is hurting their learning and grades. This is a special problem for older adolescents. At this age, the biological clock shifts and makes them stay up too late if they need to get up at 6-7 A.M. to get ready for school. Kids this age need about 9 hours of sleep a night. So what is the relationship to learning? Two things:

1. When students are drowsy during class, they can't focus attention and will not encode new information effectively. Sometimes they even fall asleep in class, which means they are not encoding anything.
2. Sleep provides an uninterrupted mental environment in which the brain rehearses the events of that day. As documented in dozens of peer-reviewed research reports, this rehearsal promotes consolidation of fragile temporary memory into more permanent form.

Now, two new studies reveal what happens during sleep to accomplish this consolidation task. Just as a computer writes to a hard drive or CD for permanent storage, the brain has to have a storage mechanism. Information in the brain resides, in real time, in the form of nerve impulses flowing around in certain networks. As long as the impulses are present, the memory is present. But if the impulse patterns change, then the information they represented is lost—unless the impulse pattern was played long enough to cause structural change in the corresponding circuitry. Scientists have known for several decades that information is stored in the junctions (synapses) between neurons. We used to think that the synapses involved in learning can grow from repeated use. Impulse patterns representing the day's experiences are replayed during sleep, providing the repetition needed to stimulate growth in the corresponding synapses. But new evidence suggests that learning does not cause the involved synapses to grow, but rather prunes them during sleep to remove irrelevant information.
One of the new studies showed that synapses in mice change structure and chemistry during sleep. In sleep, the synaptic gaps become narrower and the number of neurotransmitter receptors decreases. This may constitute a pruning process. Synapses receive multiple inputs, and a pruning process could help remove irrelevant and interfering information, thus causing a relative magnification of the memory of information being rehearsed during sleep. Another way to think about it is that sleep may provide a mechanism for "smart forgetting."
The second study by another group, also in mice, confirmed this evidence of pruning and further implicated a particular receptor, the one for the excitatory neurotransmitter, glutamate. The investigators even identified the gene that is activated to remove excess glutamate receptors.
The practical application of these findings for school children is that the more they are allowed to sleep, the more time there is for sleep to cause the synaptic changes needed to store the day's learning in the "brain's hard drive." The other, more general, implication of these studies is that the brain's anatomy and physiology are readily changed by experience, a well-established fact that scientists call "neural plasticity."

Readers may be interested in "Memory Medic's" book, Memory Power 101 (Skyhorse) and his more recent book, Mental Biology (Prometheus).


de Vivo, Luisa, et al. (2017). Ultrastructural evidence for synaptic scaling across the wake/sleep cycle. Science.  355, 507-510.

Diering, Graham H. et al. (2017). Homerla drives homeostatic scaling-down of excitatory synapses during sleep. Science. 355, 511-515.

Thursday, February 16, 2017

Managing Information to be Remembered

Do you feel embarrassed because you use such memory aids as sticky notes, calendars, shopping lists, designated places for personal items, or other shortcuts to help you remember? If so, don’t feel bad. Some recent research suggests that saving key information in specific ways can be a good idea. Not only do reminder notes, computer files, and other means of information storage make information available for later access, they also can apparently lighten cognitive load and make it easier to remember new information.

Recent experiments tested the hypothesis that saving information is a form of off-loading cognitive workload that frees the brain to be more effective at attending and remembering new information. These experiments by a team at the University of California, Santa Cruz, were inspired by prior work of others revealing that information was not remembered as well if it were saved as a computer file, presumably because participants knew they could look it up later. This finding was subsequently confirmed in other ways. This is the effect of "Memory in the Age of Google," the title of a keynote address I gave to 1,300 teachers at a conference.

But one question not addressed in the prior work was the possibility of an effect on future learning. Now a principle of proactive inhibition of memory formation has been identified in which new learning can be impaired by immediately prior conditions. Could off-loading of previously acquired information affect proactive inhibition? Saving a copy of information might reduce such inhibition by lowering the brain’s workload as it encounters new information to be remembered. Indeed, several groups had established that telling participants they don’t have to remember a list of items enhanced the memory for a second list of items. Thus, it seemed plausible to suggest that saving a list of items, as for example in a computer file, might make it easier to memorize a second list because the learner knows the saved original information can be accessed later.

The test of this idea involved 20 college students who took six trials, each involving study and testing of the contents of two PDF computer files, labeled A and B. For example, they first studied file A, but before being tested on it, they would study and be tested on file B. On half of the trials, participants saved file A after studying it, and the other half were no-save trials in which file A was exited without saving before study and testing on file B. The amount of recall on testing of file B was significantly greater on trials when file A had been saved. This was confirmed in a subsequent trial in which half of the save trials were conducted when participants were told the save procedure was not reliable and that the information in file A could be lost. As long as they trusted that file A was reliably saved, they remembered more from file B.

It seems likely that this principle could apply to other contexts, and thus there might be practical applications. By using a variety of memory saving aids (sticky notes, calendars, etc.), people gain some protection from proactive interference for new learning. And, of course, the earlier saved information is still accessible to be memorized as needed. This may well be the major advantage of taking good lecture notes, for as the learner is off-loading information as it is being saved in the notes, some of the new learning (which is also being saved in the notes) might actually become memory during the note-taking process.

Another obvious benefit is the reduction of anxiety over a concern that you might forget. You know the information is safely stored, so the brain is free to take on new learning without a degree of proactive interference that anxiety always produces. You probably can think better too, as the mind has very limited capacity to hold information in conscious working memory, which holds the information that you think with.

Dr. Klemm is author of Memory Power 101 (Skyhorse), Better Grades, Less Effort (Benecton), and Mental Biology (Prometheus).


Sparrow, B. Liu, J., and Wegner, D. M. (2011). Google effects on memory. Cognitive consequences of having information at our fingertips. Science. 333, 776-778.

Storm, B. C., and Stone, S. M. (2014). Saving-enhanced memory: The benefits of saving on the learning and remembering of new information. Psychological Science. Doi: 10.1177/0956797614559285.

Saturday, January 21, 2017

Why Music Matters

Every generation has its preferred music. In the 1920s, it was classic jazz. In the 40s it was big-band swing. In the 50s it was modern jazz, Elvis, and rock. In the 90s rap and hip-hop became popular. However, some music, such as country and classical music does not seem to be bound to a particular generation.

Whatever your generation is, you likely prefer that generation's musical genre. As we age, we can find great comfort in listening to the music of our generation, often accompanied with irritation at "that terrible noise" of the current musical fad.

Most of us know from personal experience that certain music is profoundly linked to personal memories. When we hear music from our past we not only remember the music, we often remember associated places, events, and people. This was an underlying theme of the highly acclaimed new movie, LA LA Land. If it is music we loved then, we love it now, and it feels good to hear it again. Listening to your favorite music combats the body's response to stress.

You don't even have to wait years for the benefit. I remember in college, I got exposed to modern jazz as a freshman, and years later as a graduate student got much relief from my academic stress from listening to jazz records. Now 50 years later, jazz still has the same effect on me. By the way, there is a formal scientific study showing that listening to jazz raises body levels of the feel-good endorphins and of immunoglobulin, which protects against infections.

Music has therapeutic value. The "right kind" of music soothes our frazzled nerves. Some of that effect comes from the music's rhythm. Biologically we are rhythmic creatures with all sorts of rhythms: heart and breathing rates, hormone cycles, sleep cycles, mental alertness cycles, and so on. Other musical benefits are emotional, for reasons that are sometimes hard to explain.
For seniors with dementia, music is now becoming considered as part of the therapy. A formal therapy program has been instituted by I have no vested interest in this program, but it seems to have the right idea and practical approach to helping demented patients. In Alzheimer's Disease patients, for example, music can improve mood and thinking ability and memory and reduce the need for psychotropic drugs.

A movie documentary, Alive Inside, is a story of music and memory that illustrates that musical memory lasts longer than other kinds of memory. Even in Alzheimer's and other dementias, favorite music resurrects memories that help to reawaken patients, making them feel like themselves again and socialize. Life is especially confusing to a demented person, and musical favorites provide something interpretable and pleasurable. A podcast is available at There are over 3,000 Music & Memory Care organizations in U.S., Canada, Australia, and Europe. The program provides iPods and trains volunteers to help seniors listen to their favorite music by creating a personalized iTunes play lists for iPods. The Canadian affiliates report that the program helps people who have been silent or less communicative, sad and depressed. and less mobile.

The organization surveyed its care facilities staff in 2012 who said that personalized music:
·         brought more pleasure to patients (100% of the staff respondents).
·         made their job of care easier (68% of the staff).
·         was effective for patients with depression (58% of staff) and for patients with anxiety (71% of staff).
·         reduced the use of anti-psychotic medication (53% of staff).

A review of the program by Monica Jacquez, of television KXTV, quotes Casey Simon, one of the senior care staff, as saying that "Music really makes everybody happy. It really does, and especially if you hear a song from your past, it brings back those happy memories and puts you in a place of happiness." Simon said the staff got inspired to host dance parties.

The need is great for helping seniors to enjoy life. Loss of happiness is widely experienced by seniors. Friends and spouse may have died. Children may not need you anymore. Food no longer tastes as good. Aches and pains seem to be everywhere in the body. Successful careers are over. The problems may be compounded by having to live alone. Getting old is not for wimps.
You haven't outgrown the music of your teenage years. You just need reminding. So when you are down, bring out the CDS and tapes of your favorite music. It's what I do―and it works!

Readers of this column will be interested in "Memory Medic's" e-book, "Improve Your Memory for a Healthy Brain. Memory Is the Canary in Your Brain's Coal Mine" (available in all formats from The book is devoted exclusively to memory issues in seniors.


Fancourt, Daisy, Ockelford, Adam, and Belai, Abi (2014). The psychoneuroimmunological effects of music: A systematic review and a new model. Brain, Behavior, and Immunity. 36, 15-26.

Jacquez, Monica (2016). Music program helps seniors with memory loss. ABC10 Connect. November 21.

Thoma, Myriam V. et al. (2013). The effect of music on the human stress response. PLoS One.  8(8): e70156. doi:  10.1371/journal.pone.0070156

Thursday, December 29, 2016

Thwart Stress Effects on Memory

It is well known that stress can impair memory. Everyone has had some experience of this kind. As a student suffering test anxiety, grades are likely to suffer. In high-stakes social or business interactions, the stress may well cause memory to fail us, as when Presidential candidate Rick Perry forgot the name of the agency he wanted to abolish if elected, or when we forget a friend’s name in the process of making a social introduction. How does stress do this? Is there anything we can do about it?
First, we need to know what stressful events do to the body and brain. Brain freezes, like Rick Perry's, probably occur because thinking can get so preoccupied with the stress-inducing stimuli that other thoughts cannot emerge. But other kinds of stress-induced memory impaired come from the well-known “fight or flight” response in which stress activates the release of adrenalin into the blood stream. Adrenalin has many bodily effects that support fight or flight, such as raising heart rate and blood pressure, and increasing arousal perhaps to the point of anxiety and fear. The increased attentiveness may have a fleeting beneficial effect on memory, as has been demonstrated in laboratory experiments. But the other effects of adrenalin on anxiety and distress are likely to impair memory.
The other thing that happens during stress is the activation of the anterior pituitary gland’s release of ACTH, which in turn activates another part of the adrenal gland to dump cortisol into the blood stream. In the short term, cortisol can have many beneficial effects for combatting stress, such as mobilizing white blood cells and enhancing the immune system. But cortisol binds to cells in the brain’s hippocampus, the area that converts new experiences into memory. This binding actually disrupts the memory-forming process. Ultimately, if stress continues, the synaptic regions deteriorate, making the impairment permanent.
The effects of both adrenalin and cortisol were revealed in an interesting study of mild social stress. Here, the focus was on a theory of how stress effects on memory might be thwarted by a learning technique called forced retrieval. Prior research with students, had shown, that the usual study technique of re-reading notes or text is not nearly as effective as requiring the learner to actively retrieve the information, as one might do, with flash cards, for example. Just a few months ago, I posted a blog on this forced retrieval phenomenon as a key element in “strategic studying.”
This new research was aimed at testing the possibility that forced retrieval might protect learners from the memory deficits caused by stress. In the study on the first day, 120 subjects studied a list of 30 nouns or images of nouns one at a time. Then, one half of the group restudied the items while the other half practiced retrieval by recalling as many items as they could (but without feedback telling them if they got it right). One the next day, half of each group were stressed by being required to solve hard math problems and by giving speeches in front of two judges and three peers. Then they were tested. Twenty minutes later they took a second test on items that had not been tested on the first test. The results revealed that retrieval practice yielded better results.

On the first test, we see that the stressed learners who just studied the items the day before had fewer of the items remembered on the first test given immediately after the stress. But there was no such effect on the stressed leaners who used retrieval practice during the initial learning. This protective effect of retrieval practice was evident on the second test 25 minutes later. In fact, the retrieval practice effect was better than on the first test, even though different items were tested. You may have noticed that the stressed study group on the second test did worse than they did on the first test. This is attributed to a mild effect of adrenalin, which as mentioned above can have some benefit on memory. Adrenalin’s action is immediate and is apparently swamped on the second test by the delayed release of cortisol, which shows up by the second test. Students might note that the magnitude of difference may appear small, but in percentage terms could equal to more than two letter grades (compare the two stressed groups on the delayed test).
To explain why forced retrieval works, the authors speculate that it provides better initial encoding. That is, the new information is registered more strongly if you make yourself try to retrieve it. This is consistent with the everyday experience that most of us have had wherein information that strongly grabs our attention is more likely to be remembered. Forced retrieval is a way to make ourselves pay better attention to what we are trying to lean.

Readers wanting to learn more about improving memory are urged to check “Memory Medic’s” books, Memory Power 101 and Better Grades, Less Effort.

Klemm, W. R. (2016). Strategic studying. October 9,

Smith, Amy M. et al. (2016). Retrieval practice protects memory against acute stress. Science. 354 (6315), 1046-1047.

Saturday, December 10, 2016

Base Relationships on the Present, Not the Past

Everyone has feelings about those who have been close to them: parents, siblings, spouses, and colleagues. Those feelings are usually formed from memories of past interactions with those people. When those memories are negative, they can poison relationships and lead to terrible results: family feuds, alienated siblings, estrangement between children and parents, divorce, law suits, and assorted vendettas. The saddest part of all is that research is showing that many of these negative memories can be wrong.

Memories are seldom fully literal. Memories are constructed, not recorded like an audio tape. The brain decides how an experience is to be packaged as a narrative to remember. We even generate fictions for experiences that do not involve our own inter-personal relationships. Witness the conflicting stories about how many planes struck the World Trade Center or about the Ferguson "hands up, don't shoot" imagined incident. The criminal justice system now downplays eye-witness testimony because so much of it in the past has proven unreliable. Often this happens when experiences are intense and complex, causing the over-taxed brain to jam them unthinkingly into its already formed store of memories.

Construction of false memory is especially likely during childhood, for several inevitable reasons:
·         Children do not process reality as readily or correctly as adults.
·         The brain circuitry of children changes dramatically as brains grow and re-wire, which causes many memories to be lost or corrupted.
·         Constant replay of the memory over the years leads to further alteration of the memory and the repetition confirms the memory, even when it is wrong.

A recent article in the Wall Street Journal says that we categorize memories to help define ourselves. The author says this is a good thing because it is a method for bolstering one's ego. We may, for example, construct memories to help us think of ourselves as superior, righteous, or likable. But others will construct memories that confirm a pre-existing low self-esteem, thinking of oneself as a victim, incorrigible, unlikable, or whatever. This is a well-studied phenomenon that psychologists call confirmation bias. For better or worse, we transform real experiences into memories that are a "creative blend" that mixes fact and fiction.

When we construct memories that put a negative spin on past interactions with others, we build a negative attitude toward them. Negative attitudes about others are hard to hide. Then as subsequent relationship experiences occur, they too get the negative spin, adding to the storehouse of false memories that can grow into hostility. Rubbing salt into mental wounds by rehearsing grievances year after year intensifies the memory and reinforces belief in it. Apologies and forgiveness become harder and harder to generate.

Why does the brain work this way? A Harvard study revealed that the same areas of the brain are used for remembering past events and imaginary events. A University of Dayton study showed another reason: people have an unconscious incentive to create false memories to protect themselves from threats to their beliefs about themselves. As a relatively benign example, college students who opposed increased tuition, after writing an essay that required them to defend a tuition increase, mis-remembered their initial opposition.

More serious consequences result when, as a Northwestern U. psychology professor explains, people exaggerate the negativity or misery of past experiences to impress themselves and others by their endurance of suffering or "escape" from it. Such exaggeration also occurs as responses to real-time events, as for example when people put the worst possible spin on a current experience. It makes them seem to be a bigger victim and coping with it seems like a bigger achievement.

A University of Utah psychologist says false memories take on more meaning and apparent justification when recounted to others. So as if the false memory were not bad enough, we use it to poison the reputation of others. A child who thinks parents or siblings were unfair, gains validation by telling friends about the presumed mistreatment. A worker may put a negative spin on an annual review and may feel better if he uses that memory to discredit the boss in the eyes of others.
The damage in such cases is three-fold: 1) lying to oneself prevents dealing with real solutions, 2) damaging the reputation of others is mean-spirited and unjust, and 3) spreading this kind of falsehood ultimately destroys the reputation of the perpetrator.

"Bury the hatchet" is sound advice. The more promising way to have good relationships is to base them on the present and to nurture them in positive ways for the future.

Dr. Klemm is author of the recent book,
Mental Biology (New York: Prometheus).


Krokos, Dan. (2012). False Memory. New York: Hyperion.

Shellenbarger, Sue (2016). How inaccurate memories can be good for you. Wall Street Journal. July 27. 

Wednesday, November 23, 2016

To Remember Multiple Items: Put Them in Related Groups

Memory formation and recall are greatly influenced by how items of information relate to each other. In the case of words, different words that have related categorical meanings are often easier to remember as a unit. For example, in a list of words that include spinach, cabbage, and lettuce, recalling any one of these words will assist in recall of the other two, because they have a related meaning of green vegetables. They are "semantically clustered." 

Several studies have shown that when people are asked to memorize a list of words and recall them in any order, they tend to recall words that are related. For example, in a list that contains animal names, flowers, grocery items, and historical events, a person who recalls "cat" is also likely to recall the "dog" item that was in the list. This happens because we all have a tendency to organize things by groups. Few of us capitalize on the power of this approach with a deliberate strategy to do so.

In a study of whether semantic clustering helps older people to remember, a comparison was made between 132 younger subjects (ages 18-30) and 120 older ones (60-84). In the experiment subjects were asked to memorize two lists of words, one with words presented one at a time and the other all at once so that subjects could see what words might reasonably be clustered. For the whole-list presentation, subjects were instructed on how they might use clustering.

When the groups were instructed to use semantic clustering on the second list of words, both groups showed clear and comparable improvement in recalling words presented in a whole list, as opposed to presentation one at a time. The beneficial effect was reflected in faster recall responses and in working memory capacity.

Bottom line: to remember a list of items, try to group similar items in your mind. Try it with your grocery list next time you go to the grocery store.


Manning, J. R., and Kahana, M. J. (2012). Interpreting semantic clustering effects in free recall. Memory.

Kuhlmann, B. G., and D. R. Touron. (2016) Aging and memory improvement through semantic clustering: The role of list-presentation format. Psychology of Aging. 31(7): 771-785. 

Wednesday, October 26, 2016

Learning to Be Dishonest

In this time of Presidential elections, what better time could there be to write a post about dishonesty. What makes people dishonest? What makes some people more dishonest than others?
          Any attitude or behavior, if sufficiently rehearsed, becomes a habit. Once formed, habits automate attitude or behavior, producing mental “knee-jerk” responses to the events of life. So, the key to honorable behavior, for example, is to think carefully about the attitudes and behaviors one is repeating. If it contributes to personal integrity, habit is a good thing. If repeated attitudes and behaviors are teaching you to be dishonest you will have done it to yourself―and made it lasting.
          A clear example of teaching oneself to be dishonorable comes from a new British university study showing that people become desensitized to lying. The experiment involved creating scenarios whereby people could lie. In the experiment with 80 people, pairs in separate rooms viewed a photograph of a jar filled with pennies. The photo was clear only for one person, whose task it was to advise the other person how many pennies were in the jar. The person making the estimate was told that the reward would vary on each trial, without knowing critical details about the built-in incentive structure. No feedback was provided. The more the advice was deliberately exaggerated, the more financial reward was to be given. Conditions were manipulated so that lying could benefit both partners, benefit the advising partner at the expense of the other partner, or benefit the advising partner only. There were features of the design that I think could have been improved, but that is beyond the scope of this post.
The greatest lying occurred when it benefited only the lying person. Dishonesty persisted at lower levels if the partner also benefited. There was zero lying under conditions were lying was punished by lower reward while the partner benefited.
People's lies grew bolder the more they lied. Brain scans revealed that activity in a key emotional center of the brain, the amygdala, became less active and desensitized as the dishonesty grew. In essence, the brain was being trained to lie. Thus, a little bit of dishonesty might be viewed as a slippery slope that can lead one to grow more dishonest. 
Emotions are at the core of the issue. Normally, we tend to feel guilty when doing something we know is wrong, like lying. But as we get in the habit of lying, the associated shame or guilt habituates. We get used to it and our conscience doesn't bother us so much. So, we are less constrained in our future behavior. We can't always be brutally honest, but it is now clear that each little lie or dishonest act can escalate and negatively change the person we are.
Another possibility is that positive reinforcement of behavior is involved. A well-known principle of behavior is that one tends to repeat behavior that is rewarded. Thus, if a person benefits from lying, he will likely do more of it. However, the brain area most associated with positive reinforcement, the nucleus accumbens, did not show any change in activity. The authors still asserted that lying was motivated by self-interest, because the greatest lying occurred when only the adviser benefited. However, the experiment was designed so that subjects could not know when their advice was being rewarded. Thus, the likely remaining explanation is that they just adapted to lying and it didn't bother them so much to exaggerate their estimates.
The absence of feedback was a crucial part of the design. But the authors point out that in the real world, the extent of dishonesty is greatly affected by feedback in terms of whether the deceiving person thinks there will be benefit or punishment.


Garrett, N. et al. (2016). The brain adapts to dishonesty. Nature Neuroscience. 24 October. doi: 10.1038/nn.4426

Sunday, October 09, 2016

Strategic Studying

School has started, and many students are discovering that they are not doing as well as expected. Parents and teachers may be chiding them about working harder. It might be more helpful to urge them to work smarter. This brings us to the matter of how students study.
My impression is that many students do not study effectively. Everyone knows that it is a bad idea to try to study while listening to music, watching TV, or frequently interrupting to check e-mail or Facebook and Twitter. One aspect of studying that is often under-valued is the way students test themselves to see how much they have learned. Typically, they "look over" the assigned learning content (notes, on-line videos, or reading assignments). Most students do not realize how important it is to force themselves to recall. In part, this is because they are conditioned by multiple-choice tests to recall passively, that is recognize when a correct answer is presented, as opposed to generating the correct answer in the first place.
Studies of student learning practices reveal how important to memory formation it is to retrieve information you are trying to memorize. For example, a 2008 study evaluated study and testing effects on memorizing foreign-language word pairs in one learning session of four trials, as one might do for example with flash cards.
A large recall improvement occurred if each repeated study attempt required active recall at that time, as opposed to just looking at the correct definition. Applying this finding to all kinds of learning suggests that learners should force themselves to recall what they think they have learned. Just looking at content again and again may not promote long-term learning.
Next, the investigators wanted to know whether recall is affected by focusing only on the word pairs that were incorrectly recalled. This is equivalent in a flash-card scenario, to re-studying only the words that were missed in the previous attempt. The test groups involved Study (S)(looking at each word and its paired word) and Test (T)(forced recall of each word in the pair) for either all of 40 word pairs or just the word pairs that were not recalled in the previous trial. The learners ran through the deck four successive times.  
At the end of this learning phase, students in each group were also asked to predict how many word pairs they would be able to remember a week later. It turned out that irrespective of the learning condition, predictions were inaccurate. This confirms my own experience that students are frequently poor judges of how much they know.
As for the effectiveness of initial learning, all four groups achieved perfect scores after four trials, with the largest improvement between the first and second trial. So that means they all learned the material. The issue at hand was how well they remembered when quizzed later. When given a test a week later, the two groups in which forced-recall testing was repeated in each study trial, final recall increased over the other two conditions by four standard deviations, ranging from 63 to 95% of correct recall a week later. Thus, it seems that forced-recall testing is more important for forming memories than is the studying. What this indicates is that learning occurs during forced-recall testing, and retrieval practice should be part of the initial study process.
In 2015, another group of researchers replicated these findings and further examined the effects of the varied spacing in the first study. That is, in the 2008 study, the two conditions where testing was repeated in each trial took more time because all 40 word pairs were tested. The second group of investigators was surprised that the earlier study seemed to diminish the importance of repeated studying, compared with repeated testing. One problem might have been that the original study design was "between subjects," where scores were averaged for students in different test conditions. This design meant that the elapsed time varied among the groups, because it took more time to complete four study cycles of all 40 word pairs and tested than it did when only non-recalled items were studied and/or tested. So this new study had a "within subjects" design in which every learner experienced all four ST conditions on 10 different word pairs.
The results replicated the earlier findings on the value of forced-recall testing. That is, the two groups that self-tested in each of the four study cycles had the most recall after one week. Moreover, the group that re-studied and re-tested all word pairs recalled about twice as many word pairs than did the group that only re-studied and re-tested non-recalled words. Thus it appears that restudying items that have been correctly recalled earlier is far from useless.
Both studies make it clear that how well a learner remembers soon after learning provides no assurance of how much will be remembered after a week (or longer) delay. In these studies, optimal learning occurred when an initial learning session included repeated study and forced-recall testing of all items at least four times in a row. Of course, we only have data for 40 items, and long-term memory might be affected differently for smaller or larger sets of learning material.
Bottom line:
·         Just looking over learning material can be ineffective for long-term memory.
·         Right after learning an item of information, force yourself to recall it and check to see if you got it right.
·         Conduct forced--recall testing of all information, not just the items that were previously recalled correctly.
Study should be strategic. These and other learning and memory aids are found in my inexpensive e-book on learning skills, Better Grades, Less Effort ( or the more comprehensive book, Memory Power 101 (Skyhorse).


Karpicke, J. D., and Roediger, H. I. III (2008). The critical importance of retrieval for learning. Science. 319, 966-968.

Soderstrom, N. C. et al. (2016). The critical importance of retrieval—and spacing—for learning. Psychol. Science. Dec. 16. doi:10.1177/0956797615617778.