Answer the following questions. You total page count must be at least 4 pages (this means four complete pages). All answers MUST be in your own words.1.5 Spacing. 1) Discuss the difference between k

Compared with traditional lessons in structured class­ room environments, these online approaches involve more freedom for learners to decide how and when to engage in learning, as well as greater responsibility for learners to keep themselves on track, monitor their progress and remediate their learning when necessary. This new educational landscape raises important questions about the best ways to learn information and how to know when one has learned something effec­ tively. More than 100 years of scientific research on the psychology of learning have been devoted to these questions. This research has revealed some straight­ forward techniques that enhance learning. In particu­ lar, spacing of learning opportunities across time and incorporating active retrieval of the material are both effective in boosting learning across various domains.

However, these techniques are underused by learners, in part because of false beliefs about learning and the counter ­ intuitive nature of the techniques.

In this Review, we discuss key research findings from the psychology of learning. We begin with an overview of how learning is typically measured. We then discuss spacing and retrieval practice, two strategies that pro­ duce effective learning. We focus on these strategies because of the long­ standing research showcasing their general effectiveness and straightforward applicabil ­ ity in numerous learning domains 4 – 9. Next, we discuss key findings in the research on metacognition — how learners monitor and make decisions about their own learning — focusing on ways in which metacognition can break down and how to improve it. Finally, we pro­ pose numerous directions for future research concerning the adoption of effective learning strategies, improving awareness of these strategies, and the knowledge and skills relevant to increasingly autonomous approaches to learning. Measuring learning Successful learning requires building factual knowledge as well as an understanding of how that knowledge can be integrated, utilized and applied in new situations.

Memory for basic facts and concepts is needed to build a deeper understanding of how those facts and concepts fit into a broader network of knowledge, in turn allowing advanced reasoning and application 10. Although mem­ ory for facts and concepts can be developed in the early stages of learning, a more comprehensive perspective that permits deeper understanding can be slower to The science of effective learning with spacing and retrieval practice Shana K. Carpenter 1 ✉ , Steven C. Pan 2 and Andrew C. Butler 3,4 Abstract | Research on the psychology of learning has highlighted straightforward ways of enhanc ing learning. However, effective learning strategies are underused by learners. In this Review, we discuss key research findings on two specific learning strategies: spacing and retrieval practice. We focus on how these strategies enhance learning in various domains across the lifespan, with an emphasis on research in applied educational settings. We also discuss key find- ings from research on metacognition — learners’ awareness and regulation of their own learning.

The underuse of effective learning strategies by learners could stem from false beliefs about learning, lack of awareness of effective learning strategies or the counter- intuitive nature of these strategies. Findings in learner metacognition highlight the need to improve learners’ subjective mental models of how to learn effectively. Overall, the research discussed in this Review has important implications for the increasingly common situations in which learners must effectively monitor and regulate their own learning. 1Department of Psychology, Iowa State University, Ames, IA, USA.

2Department of Psychology, National University of Singapore, Singapore City, Singapore.

3Department of Education, Washington University in St. Louis, St. Louis, MO, USA.

4Department of Psychological and Brain Sciences, Washington University in St. Louis, St. Louis, MO, USA.

✉ e- mail: sh a ca rp @ ia sta te .e d u http s://d oi. o rg /1 0 .1 0 38/ s 4 41 59-0 22-0 0089-1 0123456789();: REVIEWS NATURE REVIEWS | PSY develop 10. An important objective of research on learn­ ing is to measure these different levels of knowledge.

Doing so builds an understanding of the stages and time progression of learning, as well as the ways in which dif­ ferent learning activities might improve particular levels and types of knowledge. In measuring learning, a distinction is commonly made between knowledge retention and knowledge transfer 11. An example of retention and transfer can be illustrated using the Pythagorean theorem (Fig.  1) .

Knowledge retention is the ability to retain something in memory. One can retain the theorem, which states that in a right­ angled triangle, the length of the hypot­ enuse squared is equal to the combined squares of the lengths of the other two sides (Fig.  1a) . Knowledge transfer refers to the ability to demonstrate a broader understanding of a concept. For instance, transfer ena­ bles one to use the theorem to calculate the hypotenuse length of a right­ angled triangle with side lengths that have not been previously encountered (Fig.  1b) . Transfer is also required when knowledge is applied in a new con­ text that differs from the way in which it was originally learned. Thus, transfer is also used to apply the theorem to calculate how long a ladder must be in order to reach the second storey of a building from 5.8 m away (Fig. 1c) .

Transfer requires memory retention. Learners would not be able to find the hypotenuse of a new right­ angled triangle without first remembering the theorem.

However, learners could successfully remember the theorem but fail to recognize its relevance in a new situ­ ation. Successful transfer depends on sufficient memory for information as well as the ability to understand the relevance of that information in a new situation. Thus, transfer demonstrates a more advanced level of learning than retention. Transfer can fail owing to deficiencies in memory retention, the ability to connect remembered information to a current situation, or both 12.

Both retention and transfer are important to learning.

In academic contexts, a great deal of factual information must be retained, such as theorems, principles, terms and definitions, scientific names and foreign language vocabulary. However, an important goal of learning is to utilize and apply knowledge, so transfer might be con­ sidered the ultimate goal. Transfer can occur in numer ­ ous ways, ranging from fairly simple to more complex 12.

Simple transfer is sometimes called ‘near’ transfer (for example, applying a mathematical formula to a new problem) (Fig.  1b) and complex transfer is called ‘far’ transfer (for example, applying a solution or principle from one knowledge base to another) (Fig.  1c) .

A long­ standing focus of research on the psychology of learning has been to uncover and understand strat ­ egies that build effective retention and transfer. The strategies of spacing and retrieval practice have been widely studied in both academic and real­ world con­ texts, across a multitude of learning domains, involving learners from all stages of life. Below we highlight some of the key research findings in these areas, focusing pri­ marily on studies conducted in real­ world educational environments. Strategies for effective learning Much like a fitness routine designed to achieve a particu ­ lar goal, such as weight loss or miles walked in a year, a successful learning routine requires knowing what to do and when to do it. We review key research findings on two of the most effective strategies for learning accord­ ing to psychological research. Spacing is a way to struc­ ture or schedule learning activities over time (when to engage in learning), whereas retrieval practice is a learn­ ing activity that can be incorporated within a broader structured plan (how to learn effectively).

Spacing out learning across time. To build durable knowledge, learners have to repeatedly study and use the information that they are trying to learn. Whether trying to learn definitions for scientific terms, grammar rules or how to use a computer program, learners have to revisit the material multiple times in order to develop proficiency. This need is visible even in the early years of formal education, when young children are given repeated practice in reading and mathematics to develop these fundamental skills. However, few people consider the timing of this repeated practice — one might logi­ cally assume that the timing does not matter so long as learners get a sufficient quantity of practice. As it turns out, the timing of practice greatly influ­ ences learning success, even for the same overall quan­ tity of practice. Repeated practice opportunities that are spaced apart in time are more effective than the same number of practice opportunities that occur closer together in time. This finding — known as the spacing effect or the distributed practice effect — was first docu­ mented more than 100 years ago 13 and has been demon­ strated in several hundred studies5, making it one of the most reliable and robust findings in the psychology of learning. According to a 2006 meta ­ analysis, the benefits of spacing on retention of information over at least 1 day can be sizeable, sometimes with an effect size of Cohen’s d greater than 1.0 (reF . 9). Across the lifespan, spacing effectively enhances learning in numerous domains (Table  1) . These range from 3­ year­ old children learning about basic concepts and categories 14 up to 60­ year­ old adults learning new knowledge and skills 15. a bc ab Hypotenuse = c Pythagorean theorem c 2 = a2 + b2 90° 4 5.8 m 3 x x 2 = 42 + 32 6.4 m Fig. 1 | Knowledge retention and transfer. Pythagorean theorem describes the rela- tionship between the lengths of three sides of a right- angled triangle. a–c | A knowledge retention test would require students to remember some piece of information that they have learned about the theorem, such as the formula for finding the length of the hypot- enuse (part a). A knowledge transfer test would require students to answer a novel ques- tion that demonstrates understanding or application of the learned information. This might involve calculating the hypotenuse using values given for the other two sides of a new triangle (part b) or applying the theorem to a new situation involving a real- world example (part c).

0123456789();: www.nature.com/nrpsychol REVIEWS Table 1 | selected studies showing statistically significant effects of spacing across the lifespan learner level learning materials Implementation of spacing Ref.

Preschool or younger ( < 5 years old) Pictures Pictures presented twice, separated by two, four or eight intervening pictures 160 Toy namesThree presentations per toy spaced apart by 30 s 14 WordsFour exposures spaced apart by 3 days 161 Elementary school (5–10 years old)Credibility judgements Three lessons spaced 1 week apart 18 Foreign language translationsTwo learning sessions separated by 1 week 162 Grammatical rulesTen practice trials spaced across 5 or 10 days 163 Mathematical skillsFour daily sessions spaced 2–4 h apart, repeated over 18 days 164 Pictures Pictures presented twice, separated by two, four or eight intervening pictures 160 Scientific principlesFour lessons spaced across 4 consecutive days 17 Vocabulary wordsTwo lessons spaced 1 week apart 28 Middle school (11–13 years old)Biology lessons Four lessons spaced 1 week apart 42 Credibility judgementsThree lessons spaced 1 week apart 18 Foreign language translationsTwo sessions spaced apart by 1 day 165 Mathematics, algebra and geometryProblems per topic spaced across eight assignments over 15 weeks 19 Mathematics, permutations and diagramsThree practice sessions spaced 1 week apart 16 High school (14–18 years old) Foreign language translations Three practice periods spaced across 3 consecutive days 166 Mathematics, geometryProblems per topic spaced across seven assignments over 6 weeks 20 Physics problemsEach practice problem spaced apart by 1 day 167 Writing in shorthandMultiple exercises spaced apart by up to five successive lessons 168 UndergraduateAnatomy course Three learning sessions spaced across 1 week 169 Artists’ painting stylesSix examples per artist, presented with intervening examples 170 Educational textsTwo readings separated by 1 week 171 Engineering problemsThree homework sets spaced apart across 3 weeks 172 Face–name pairsFour presentations per pair, spaced apart by one, three or five intervening items 173 Foreign language verb conjugationTwo sessions spaced apart by 1 week 174 Grammatical rulesThree sessions spaced apart by 1 or 4 weeks 175 Mathematics, pre- calculusThree quizzes spaced apart by 1–2 weeks 26 Mathematics, permutationsTwo practice sessions spaced apart by 1 week 176 Meteorology lessonsTwo sessions spaced apart by 8 days 27 Natural categoriesSix examples per category, presented with intervening examples 177 Physics problemsThree problems per topic spaced apart by 2 days or more 21 Piano melodiesThree practice sessions separated by 6 or 24 h 178 Pictures Pictures presented twice, separated by two, four or eight intervening pictures 160 StatisticsThree practice sessions, spaced apart by 2 or 5 days 179 Visuospatial memory taskFour practice trials spaced apart by 15 min each 15 Word pairs Four practice sessions spaced across 4 consecutive days 180 Word- processing skillsTwo practice sessions spaced apart by 10 min 181 PostgraduateCardiopulmonary resuscitation skills Multiple practice sessions, each spaced apart by up to 1 month 182 Nutrition knowledgeFour learning sessions, each spaced apart by 1 week 22 Pharmaceutical namesTwo sessions of retrieval practice, separated by 2, 3, 4, 7 or 8 weeks 183 Surgical proceduresFour training sessions, each spaced apart by 1 week 23 Urology courseEleven to thirteen learning exercises, each spaced 1 week post lesson 184 Older adults ( > 50 years old) Artists’ painting styles Six examples per artist, presented with intervening examples 185 Motor skill taskNine practice trials spaced apart by 43 s each 186 Visuospatial memory task Four practice trials spaced apart by 15 min each 15 Word pairs Word pairs presented twice, separated by 1, 4, 8 or 20 intervening pairs 187 0123456789();: NATURE REVIEWS | Psychology REVIEWS In the design of a typical study on the spacing effect, two groups of learners have at least two opportunities to study information (Fig.  2a) . These opportunities can occur either close together in time (massed learning) ( Fig.  2a , top row) or farther apart in time (spaced learn­ ing) ( Fig.  2a , bottom row). At a later point, learning is assessed for both groups. Even though the overall quan­ tity of practice is the same between the two groups, learners who engaged in repeated practice that was spaced out typically show better performance on the later test. As discussed in more detail later in this sec­ tion, these benefits occur for both retention and transfer of knowledge. Spacing effects have been explored in both laboratory­ based and school­ based studies. Studies conducted in schools confirm that spacing can be a powerful learning strategy. In one study, spacing signifi­ cantly boosted mathematics knowledge in middle school students (11–12 years old) 16. Students worked through 12 practice problems on 2 topics by completing 4 practice problems per day for each of 3 days spaced apart by a week (spaced group) or the same 12 practice problems on the same day (massed group). Four weeks after fin­ ishing the practice problems, both groups were given a test containing new problems on the same topics; the spaced group significantly outperformed the massed group, scoring about twice as high (effect size of Cohen’s d = 0.61).

Spacing benefits learning across domains and levels of education. In one study, elementary school children (5–7 years old) learned scientific principles associated with food chains (for example, the tendency for larger animals to eat smaller animals) through four lessons, with different spacing across three groups of students.

Lessons occurred once per day across 4 days (spaced group), twice per day across 2 days (clumped group) or with all four lessons on the same day (massed group) 17.

On a test given 1 week after the lessons, children in the spaced group significantly outperformed children in the clumped and massed groups (with effect sizes ranging from Cohen’s d = 0.38 to d = 1.41). Another study showed that children at the elementary school and middle school levels (9–12 years old) learned how to evaluate the credibility of information on websites more effectively if they received three lessons that were scheduled 1 week apart rather than 1 day apart 18. At the middle school and high school levels (students who are typically about 11–17 years old), the advantages of spacing have been observed when including practice mathematics problems from previous lessons within current lessons covering different topics 19, 20 .

Spacing also benefits learning at the university and postgraduate levels. In one study, undergraduate phys­ ics students completed three weekly homework assign ­ ments in which questions on a given topic appeared either all in the same assignment or spread out across the three assignments and completed on different days 21 (Fig.  2b) . On a later surprise test containing novel prob­ lems about the same concepts, students scored signifi­ cantly higher for the topics that were spread across the different homework assignments than within the same assignment (effect sizes of Cohen’s d = 0.40 and d = 0.91 for the first and second half of the course, respectively).

Spacing enhanced students’ memory for the formulas that were relevant to the problems, as well as students’ use of the correct strategies to solve the problems. At the postgraduate level, spacing benefits medical students learning nutrition information 22 and surgical tasks 23, 24 .

In one study, medical students completed three blocks of hands­ on surgery training all on the same day or once per week across 3 weeks 25. On tests given both 2 weeks and 1 year after the training, the group that completed the blocks once per week performed better and faster than the massed group. The benefits of spacing are long­ lasting. One study showed significant benefits of spacing on pre­ calculus a Basic design of spacing effect study b Design of a study involving spacing in a physics course c Results Repeated learning close apart in time First learning opportunity Time passes Time passes Final test Surprise test Surprisetest Second learning opportunity First learning opportunity Time passes Final test Second learning opportunity Repeated learning farther apart in time Had massed homeworkproblems Had spaced homework problems 60 50 40 30 20 10 0 Correct answers on surprise test (%) Massed homework problems Spaced homework problems Assignment 1 Assignment 2Assignment 3 A er 4 weeks ATOPIC Problem 1 ATOPIC Problem 2 ATOPIC Problem 3 BTOPIC Problem 1 BTOPIC Problem 2 BTOPIC Problem 3 CTOPIC Problem 1 CTOPIC Problem 2 CTOPIC Problem 3 ATOPIC Problem 1 BTOPIC Problem 1 CTOPIC Problem 1 BTOPIC Problem 2 DTOPIC Problem 1 CTOPIC Problem 2 ATOPIC Problem 2 ETOPIC Problem 1 FTOPIC Problem 1 Further assignments Further assignments Fig. 2 | The spacing effect. a | In studies of the spacing effect, some learners complete multiple learning opportunities close together in time (top row), whereas other learners complete the same opportunities spaced farther apart in time (bottom row). After a set interval, learners are given a final test.

b | In an undergraduate physics class, students learned about various topics and then completed three homework assignments per week 21. Homework assignments comprised either a single topic, such that students worked through problems pertaining to a given topic on a single day in a massed fashion (top row), or different topics, such that students worked through problems pertaining to a given topic across different days in a spaced fash- ion (bottom row). c | Spaced homework assignments produced significantly better performance than massed homework on a transfer test (with novel problems) 4 weeks after the beginning of practice. Part b is adapted from reF. 65, CC BY 4.0 (h ttp s:/ /c re ativ e co m mons.o rg /li c e n se s/b y/4 .0 /).

0123456789();: www.nature.com/nrpsychol REVIEWS learning in an undergraduate engineering course. Spaced quizzes led to better performance on the end of term examination in the same course and also on an exam­ ination 4 weeks later in a follow ­ up course 26. Spacing benefits have been observed 35 days after learning for critical thinking 18, several weeks after learning for sci­ entific knowledge and vocabulary 27, 28 , several months after learning for US history facts 29 and up to a year after learning for general knowledge facts30.

According to theories of the spacing effect, the extra time between learning sessions could promote learning by providing a mental break that encourages more effective attention 31, 32 . Spacing study sessions also creates distinct learning experiences with unique contextual features (such as the learning environment or the learner’s subjective internal state) that can serve as memory cues 33, 34 . Spaced study sessions increase the need for learners to retrieve information from earlier sessions 35, 36 , engaging the benefits of retrieval practice, as discussed in the next section. Finally, time­ dependent neural consolidation processes might also contribute to the spacing effect 37. These theoretical accounts are not mutually exclusive and the proposed processes might operate simultaneously. Spacing benefits both memory retention and trans­ fer. For example, spaced practice for the definitions of new vocabulary words benefits later retention of the meanings 38. Spaced practice also builds near and far trans­ fer proficiency. For example, spacing benefits application of mathematics procedures to new problems 16, 19 , applica­ tion of a scientific principle from one domain to another 17, diagnoses of psychiatric disorders for new individuals39 and proficiency of surgical skills in new situations 23.

Although spacing is beneficial across a range of learning activities, there is no universal ideal spacing schedule. Longer spacing schedules can be beneficial after information is already well learned and must be retained over a long delay 30. However, longer spacing schedules can be less effective when information is not yet well learned, probably because of learners forgetting the information across sessions 40, 41 . Because spacing increases the risk of forgetting between learning ses­ sions, spaced learning activities should provide suffi­ cient practice with the material to permit any forgotten information to be relearned. Although it is not possi­ ble to anticipate the perfect spacing schedule, effective spacing schedules typically involve providing sufficient practice with the learning material during the learning sessions and enough time between sessions such that the information is still familiar but not fresh in the mind.

This situation creates the need to retrieve the previ­ ous learning experience during each practice session, engaging the beneficial effects of retrieval (which we discuss in the next section). Illustrating a range of effec­ tive spacing schedules, classroom studies have observed benefits of engaging learning activities (for example, practising to recall or apply information being learned) that are spaced apart by anywhere from 1 to 7 days 16, 17,28,42 .

Retrieving information from memory. A second effective learning strategy involves memory retrieval. Bringing memories back from long­ term storage into conscious awareness is frequently thought of as occurring after learning is complete, in order to remember something that was learned previously. As such, it might seem counter ­ intuitive to regard retrieval as part of the learn­ ing process. However, it is possible to deliberately engage in the retrieval of memories while learning new infor ­ mation. For example, rather than reading a textbook chapter multiple times, one can read the chapter first, set it aside and then attempt to recall its contents from memory. Retrieval practice can take many forms, includ­ ing completing practice tests, quizzing with flashcards or open­ ended writing of remembered information.

When compared with study strategies that do not involve recalling information, retrieval practice typically generates more durable and accessible memories. This finding — called the retrieval practice effect or the testing effect — has been demonstrated in more than 200 studies from over a century of research 7 ,43– 45 and is also regarded as one of the most robust findings in the psychology of learning (Table  2) . Multiple meta­ analyses confirm that the benefits of memory retrieval are robust, with effect sizes of Hedges’ g = 0.50–0.63 for memory retention 4,45 and comparable effect sizes for transfer 7 ,46. Retrieval prac­ tice benefits learning across the lifespan, in individuals ranging from 18 months old 47, 48 to well over 60 years old 49.

In a typical study on retrieval practice, learners first have an opportunity to study, read or otherwise learn some information (Fig.  3a) . Next, that informa­ tion is learned again using one of two approaches. One approach involves restudying, re ­ reading or another strategy that does not involve memory retrieval. In the other approach, learners attempt to retrieve the material.

After a period of time, learning is assessed. Typically, learners who used retrieval practice are better able to remember the information than those who did not. A single session of retrieval practice can generate memory improvements that persist for 9 months 29, and the posi­ tive effects of retrieval over multiple sessions can last for at least 8 years 50, 51 .

In some studies, learners have the opportunity to check whether they recalled information accurately after retrieval practice. For instance, they might view the cor ­ rect answers or revisit the original learning materials.

These feedback opportunities 52 typically increase the effectiveness of retrieval practice45, 53,54 . Learners who use retrieval practice followed by feedback typically perform even better on subsequent assessments than those who use retrieval practice alone. The improvement is likely to stem from instances when learners have difficulty retrieving accurate or complete information; feedback can be crucial to help correct inaccuracies and fill in knowledge gaps 45, 55 .

Research conducted in school­ based settings con­ firms the value of retrieval practice during learning. In one study, third­ grade students (8–10 years old) read an educational text about the Sun, then read the text a second time (the restudy group) or recalled key facts from the text by taking a fill­ in­ the­ blank practice test (the retrieval practice group) 56. A week later, the restudy group performed poorly on a test, with an average score of 53%. The retrieval practice group performed sub­ stantially better, with an average score of 87% (an effect 0123456789\(\);:

NAREVIEWS | PSY REVIEWS Table 2 | selected studies showing significant effects of retrieval practice across the lifespan learner level learning materialsImplementation of retrieval practice Ref.

Preschool or younger (< 5 years old)Picture names Cued recall test followed by restudy or immediate answer feedback 188 Toy names Verbal cued recall test 189 Video demonstrationsRe- enactment of demonstrated behaviours 47 Elementary school (5–10 years old) Educational textsFill- in- the- blank test 56 Map featuresMap- based cued recall test with feedback 190 Picture names Verbal free recall test followed by restudy 191 Spelling wordsCued recall test with feedback 58 SymbolsCued recall test with feedback 192 Word listsWord stem- completion test 193 Middle school (11–13 years old) Botanical featuresCued recall test involving filling in a diagram 78 Definition–word pairsCued recall test with feedback 194 Educational textsFree recall test 195 Foreign language translationsCued recall test with feedback 194 History factsCued recall test with feedback 29 Science course materialsMultiple- choice clicker test with feedback 196 High school (14–18 years old) Educational textsMultiple- choice and short answer test 197 History course materials Multiple- choice and short answer clicker test with feedback 59 Mathematical facts, procedures Short answer tests followed by restudy 198 Science and history factsMultiple- choice test 199 Science conceptsMultiple- choice and true–false tests 200 Word lists Recognition test during verbal shadowing task 78 Undergraduate Anatomy termsShort answer test with or without feedback 201 Biology courseMultiple- choice clicker quizzes with feedback 62 Biology facts Short answer test with feedback 202 Biology processesShort answer test with feedback 53 Chemical engineering problemsScenario- based problem- solving practice test 203 Deductive inferences Fill- in- the- blank or free recall test with feedback 66 Educational texts Short answer test with feedback 67 Face–name pairsCued recall test 173 Foreign language translationsOral cued recall with feedback 204 History factsShort answer or multiple- choice test with feedback 202 Map features Map- based covert cued recall test with feedback 205 Map locations Virtual judgement of relative direction test with or without feedback 206 Mathematical functions Function estimation test with feedback 207 Natural categoriesVerbal cued recall test with or without feedback 208 Neuroscience courseMultiple- choice or short answer test with feedback 209 Psychology course Multiple- choice or short answer test with feedback 210 Scientific method Free recall test followed by restudy 211 Spelling wordsCued recall test with feedback 212 SymbolsCued recall test 213 Word listsFree recall test 214 Word pairsCued recall test with feedback 215 Word tripletsCued recall test with feedback 216 Video lecturesMultiple- choice or short answer test with or without feedback 217 0123456789();: www.nature.com/nrpsychol REVIEWs size of Cohen’s d = 2.87). Retrieval practice determined whether students acquired relatively limited or more comprehensive knowledge of the text. Other studies exemplify the benefit of retrieval prac­ tice across a wide range of educational contexts, at differ ­ ent academic levels and with many subjects. For instance, in a study of word spelling, first to third ­ grade students in the United States (6–8 years old) consistently learned dif­ ficult spelling words more effectively after taking practice tests with feedback than after repeatedly copying cor ­ rectly spelled words 57, 58 . In some cases, the improvement in spelling scores after the use of retrieval practice was more than twice that of copying. Classroom studies at the middle school and high school levels (students aged 11–16 years and older) show consistent benefits of quizzes — conducted online, using paper and pencil or via audi­ ence response systems — over restudying for biology and history materials 59, 60 . In those studies, retrieval practice typically improved unit and end of semester examina­ tion scores by a full letter grade (approximately 10%).

Similar results have been reported for the use of retrieval practice in university­ level biochemistry 61, physiology 62, psychology 63 and statistics courses 64.

Retrieval practice can also enhance learning at the postgraduate level. In one study, first­ year medical stu­ dents learned about four neurological conditions and then studied review sheets or took short answer prac­ tice tests before further studying (the latter constituting a retrieval practice with feedback condition) 65 (Fig.  3b) .

They repeated this procedure across four consecutive weeks. Six months later, when asked to propose treat­ ments for new clinical scenarios, the students recalled relevant information more accurately and proposed more appropriate treatments for conditions that they had learned using retrieval practice than from studying only (effect size of Cohen’s d > 0.70) (Fig. 3c) .

Retrieval practice can be successfully implemented in many ways, including with free recall 66, multiple­ choice 59, short answer 67 and true–false 68 quizzes or tests, as well as with online learning platforms 69, virtual flashcard programs 70 and audience response systems 62. Even more esoteric methods of practising retrieval, such as playing games that incorporate memory retrieval 71 and men ­ tally recalling information without producing an overt response 72, can also yield learning benefits. In most cases, the benefits of retrieval practice have been demonstrated by comparison to relatively passive strategies such as restudying, re­ reading or copying information 45. However, advantages of retrieval practice have also been observed against such active learning strategies as note­ taking 73 and concept mapping 74. Combining retrieval practice with learning activities that require the generation of new content 75, 76 , such as thinking of examples, can yield even greater learning benefits than simple retrieval alone 77.

According to theories of retrieval practice, there are multiple ways in which retrieval might promote learning.

By one account, retrieval practice is beneficial because other learning methods do not involve retrieval, whereas all tests — and virtually all situations that require using previously learned knowledge or skills — do. Hence, there is a benefit to performing retrieval both when one is learning or studying and at a later test 78. Alternatively, learners might remember contextual aspects of the infor ­ mation to be learned during retrieval practice that help them retain it 79. By yet another account, the retrieval pro­ cess might involve recall of not only correct information but also other information (for example, a learner’s prior knowledge or thoughts) that helps to serve as memory cues for the learned information at a later test 80, 81 . The act of retrieval could also create a new memory for the retrieval experience that is distinct from the memory of initially encountering the information 82, or might increase the number of neural pathways that can be used to access correct information 83. Finally, retrieval prac­ tice could indirectly benefit learning by revealing what learners do and do not know 84 ,85 , and therefore help them make effective use of feedback. These theories are not mutually exclusive, and more than one of these processes is likely to operate in a given learning situation. Retrieval practice benefits memory retention and transfer when knowledge must be used in a similar way to how it was learned (near transfer) 46, 86,87 . However, findings have been mixed in situations approaching far transfer. For example, some studies show that retrieval practice for deductive reasoning problems does not necessarily enhance the ability to draw inferences from individual premises that were studied 88, but engag­ ing in multiple rounds of retrieval practice benefits both memory for the premises and the ability to draw inferences from them 66, 89 . In the domain of procedural problem­ solving, novice learners typically acquire and apply solutions to new problems better if they study fully learner level learning materialsImplementation of retrieval practice Ref.

Postgraduate Anatomy and physiologyFree recall test followed by restudy 218 Cardiac resuscitationPhysical practice test involving simulated cardiac arrest scenario 219 Dental abnormalitiesMultiple- choice test with feedback 220 Neurological conditions Short answer test with feedback 65 Orthodontics proceduresClinical scenario test with feedback 221 Older adults (>50 years old) Face–name pairs Oral cued recall test with feedback 222 Prose passagesMultiple- choice test 223 Scene imagesRecognition test 224 Word pairsCued recall test with feedback 49 Table 2 (cont.) | selected studies showing significant effects of retrieval practice across the lifespan 0123456789();: NATURE REVIEWs | PSYCHOLOGY REVIEWS worked examples without engaging in any retrieval, as opposed to using retrieval practice by attempting to solve problems on their own 90,91 . However, when learners practise repeatedly retrieving the same problem scenario and the steps required to successfully solve it, memory for solution procedures and the ability to solve similar problems is improved 92.

Studies of analogical problem­ solving directly target the ability to transfer a solution learned in one domain (for example, the strategy that a military general should take to avoid landmines while capturing a fortress) to a different domain (for example, the strategy that a surgeon should use to remove a tumour while avoid­ ing damage to healthy tissue). Although one study found that retrieval practice did not facilitate solution transfer 93, a follow ­ up study found that retrieval prac ­ tice enhanced memory for the solution and the ability to transfer it, but only when learners were told that the pre­ vious solution could be relevant 94. Other research shows that when a hint is provided, retrieval­ enhanced mem­ ory for a solution or procedure facilitates its transfer to a new domain 67. Thus, although retrieval practice does not automatically enhance the ability to notice the relevance of, and decide to apply, information in a new situation, it can contribute to transfer by enhancing memory for information that is ultimately needed for transfer 12.

Retrieval practice is most likely to be effective if it entails genuine effortful attempts to recall information.

In addition, retrieval is most beneficial when it is rea­ sonably successful at bringing accurate and relevant information to mind (particularly important when no feedback is provided) 95 ,96 . Moreover, as discussed next, using retrieval practice across multiple sessions sepa ­ rated by several days or even weeks can generate even more potent and long­ lasting learning than massed retrieval practice 97. Combining spacing and retrieval.

Spacing and retrieval practice can be combined to enhance learning more effectively than either strategy alone. Retrieving infor ­ mation repeatedly over spaced time intervals produces durable and long­ lasting benefits to learning, compared with simply reviewing the information over the same time intervals 65, 98 . Retrieving information over longer spacing intervals is also more effective than retrieving it after shorter spacing intervals 29, 97,99 .

The combined powers of retrieval and spacing form the method of successive relearning. First introduced four decades ago 100, successive relearning is becoming known as a straightforward and effective learning strat­ egy, particularly for building retention of factual mate­ rials (for example, vocabulary terms and definitions) 101.

Successive relearning involves an initial session in which learners try to retrieve the information they are learn­ ing and then receive feedback to check their accuracy, repeating retrieval practice until they are able to recall all of the information to a predetermined criterion (for example, 100% correct). This initial session is followed by additional relearning sessions of retrieving the infor ­ mation followed by feedback until the information can be recalled again to the same criterion. Long­ term learning is best attained when relearning sessions are spaced apart in time 50 ,102 . For example, one study reported significant benefits when undergraduate students engaged in successive relearning of introduc­ tory psychology terms and definitions every few days, compared with engaging with the material the same number of times without trying to retrieve it 70. Another study found that undergraduate students’ examination grades in an upper ­ level biopsychology course were enhanced by more than a letter grade after engaging in successive relearning of course information every few days, compared with using their own methods of c Results Learning does not involve practising retrieval from memory Non-retrieval-based study strategy Practise retrieving information Learning does involve practising retrieval from memory Learn topic using review sheets Learn topic using retrieval practice Week 1 Week 2 Initial learning session Study review sheet Week 3 Week 4Six months later Practice test, study review sheet Study review sheet Practice test, study review sheet Study review sheet Practice test, study review sheet Initial learning session Study review sheet Practice test, study review sheet a Basic design of retrieval practice study b Design of a study involving retrieval practice with medical students First learning opportunity Time passes Final test First learning opportunity Final test Time passes Studied review sheets Used retrieval practice 40 35 30 15 5 20 10 15 0 Correct answers onapplication test (%) Application test (clinical scenario) Application test (clinical scenario) Fig. 3 | The retrieval practice effect. a | In retrieval practice studies, learners are first given an opportunity to learn some material and then have an opportunity to review that material. This review consists of viewing or re- reading the same material again (upper row) or trying to retrieve that material from memory (bottom row). b | Design of a retrieval practice study with medical students 65. For each of four neurology topics, students first experienced an initial learning session. At the end of that session and during three more sessions over the next 3 weeks, they studied a review sheet (top row) or performed retrieval practice before studying the review sheet (bottom row). c | Students showed better performance for topics that had been learned using retrieval practice than only review sheet practice on a clinical application test (which assesses transfer of learning) administered 6 months later. Part b adapted with permission from reF. 65, Wiley.

0123456789();: www.nature.com/nrpsychol REVIEWS studying 103. Although the benefits of successive relearn­ ing (compared with the same quantity of learning within a single session) might be reduced for the learning of skills such as application of mathematical procedures 104, the technique seems to be quite effective for enhanc­ ing memory retention of fairly straightforward factual information. The power of successive relearning can be boosted by engaging in extra retrieval practice in the first session.

In one study, undergraduate students practised recalling introductory psychology terms and definitions followed by feedback until they recalled each correctly either once or three times, and then engaged in three more relearning sessions in which they recalled each term correctly once 105 (Fig.  4) . Although recalling each term correctly three times in the first session was harder and took more time, this extra work paid off. Information that had been recalled correctly three times in the first session was easier to recall again in all subsequent relearning sessions (Fig.  5) and more likely to be accurate on the first attempt than information that was only recalled once.

Specifically, the items that received extra early retrieval practice were recalled on the first try about 15% bet­ ter 2 days later in the first relearning session (an effect size of Cohen’s d = 0.63), and an advantage of extra early retrieval practice persisted over the subsequent two relearning sessions 8 and 10 days later. In summary, spacing and retrieval practice benefit learning in various domains across the lifespan. Retrieval practice is a learning activity, and spacing is a way of scheduling the timing of learning activities. Spacing ben ­ efits both retention and transfer of knowledge, whereas retrieval benefits retention but produces limited bene­ fits on far transfer. Successive relearning combines the benefits of spacing and retrieval and boosts memory retention for factual information. Metacognition of strategy use The effective use of learning strategies such as spac­ ing and retrieval depends on learners’ metacognition:

the ability to think about one’s thinking and regu­ late decisions accordingly. Learning strategies can be counter ­ intuitive and require effort to plan and initiate.

Given the fundamental importance of metacognition to many aspects of mental functioning, it is studied in vari ­ ous subfields within psychology (for example, cognitive, educational, developmental and clinical psychology).

Although the lineage of research in many of these sub ­ fields can be traced to a common beginning 106, metacog­ nition is now conceptualized somewhat differently across subfields 107, 108 . We focus on perspectives from cog­ nitive and educational psychology on the use of effective learning strategies and self ­ regulated learning. Broadly speaking, self­ regulated learning refers to the cognitive, motivational and affective processes that enable learn­ ers to plan, monitor and adapt their learning, including metacognition. We conclude this section by discussing how metacognition can be improved, incorporating perspectives from both subfields.

Perspectives from cognitive psychology. Within cognitive psychology, metacognition of learning often includes awareness (also known as monitoring), or a learner’s knowledge about their own learning, and regu lation (also known as control), or the learner’s decisions or actions. For example, a student’s metacognition when studying for a French examination might include awareness that they know present­ tense verb conjuga­ tions well, but less confidence about their knowledge of past­ tense conjugations. As a consequence, the stu­ dent might decide to focus their studying on past­ tense conjugations. The outcome of a learning experience depends on learners’ understanding of their own learning (monitor ­ ing) and making the right study decisions (control), and therefore accurate metacognition is a critical element of effective learning. However, metacognition is often inaccurate. With regards to monitoring, when learners are asked to judge their confidence in their knowledge or to predict how well they will perform on a test, their judgements and predictions often exceed their actual performance. In a study involving memory for simple pictures, 89% of first­ grade children (6–7 years old) pre­ dicted that they would successfully recall all of the pic­ tures they were shown, but on the test they only recalled about half of the pictures 109. Although metacognitive ability develops from childhood to adulthood 110, 111 , over ­ confidence occurs at all levels of education beginning in primary school, with students over ­ predicting their own performance on assessments and examinations in various subject areas 16, 109, 112– 114 .

Learners also often demonstrate poor metacognitive control and make suboptimal decisions during learn ­ ing. Based on surveys of students’ study behaviours, few students engage in spacing out their studying over time but, instead, tend to ‘cram’ their studying within a few days of an examination 115. Although many students at all levels of education make use of practice testing in the form of flashcards and self­ quizzing, most students report using these strategies to find out how well they Session 1 (day 1) Successive learning Practise recall until correct 1× Practise recall until correct 3× Study terms and definitions Study terms and definitions Successive relearning with extra retrieval practice Practise recall until correct 1× Practise recall until correct 1× Practise recall until correct 1× Final test Session 2 (day 3) Session 3 (day 8) Session 4 (day 10) 5 weeks later Fig. 4 | successive relearning paradigm. In this example study, undergraduate psychology students practised recalling terms and definitions until they got each one right either once or three times 105. Students then completed three additional relearning sessions every few days in which they practised recalling each definition again until they got it correct once.

0123456789();: NATURE REVIEWS | PSYCHOLOGY REVIEWS know the information and not as a way of improving their learning, reflecting a lack of awareness of the direct benefits of retrieval practice 116–118 . Observational data on student behaviours in undergraduate courses also reflect underuse of spacing and retrieval strategies 119, 120 .

Faulty metacognition could arise from several dif­ ferent sources. One source is lack of knowledge about learning strategies. Indeed, students often lack knowl ­ edge about which learning strategies are effective 121 ,122 and seldom receive explicit instruction about how to learn effectively 123, 124 . This instruction could be provided in schools, but teachers also often lack awareness of effective learning strategies 125. At the K–12 level, teacher training often focuses on domain content and pedagogi­ cal content knowledge at the expense of domain general learning principles and strategies 126. Higher education instructors receive little, if any, formal training on how to teach, let alone how to support learners in developing their ability to learn effectively. Another possible con­ tributor to poor metacognition is the fact that common intuitions about learning tend to run counter to the way in which learning actually works (box  1) .

In summary, the cognitive psychology perspective on learning strategy use has primarily focused on the role of metacognition in enabling learners to monitor and con­ trol their cognitive processes. We now turn to describ­ ing the educational psychology perspective, which also includes metacognition as a central component but con­ ceptualizes strategy use within a broader set of cognitive, motivational and affective processes.

Perspectives from educational psychology. Within educational psychology, the interactions between metacognitive awareness and learning strategy use are situated within the broader concept of self­ regulated learning 127, 128 . From this perspective, self­ regulated learn­ ing is a complex, multidimensional process that involves setting goals, planning, self­ motivating, monitoring learning and self­ reflecting, among other elements 129,130 .

Learners might be self­ regulating consciously or unconsciously, more effectively or less effectively, but are always engaging in some form of self­ regulation while learning. Strategy planning and use is central to this larger process, which in real­ world learning situa­ tions can be complicated by numerous factors (Fig.  6) .

The understanding of when and how to use different strategies is critical because the optimal implementation of a given strategy can vary across contexts 131. That is, the same general strategy can be used in different ways.

Factors such as the nature of the materials to be learned (for example, domain, type or complexity), the nature of the learning activity (for example, reading a textbook or watching an educational video) and the assessment (for example, taking a multiple­ choice examination or writing an essay) need to be considered when planning the use of learning strategies. Effective high­ level planning for learning can be compromised if learners do not take all of these factors into account or if they forego a plan entirely. Furthermore, as learners carry out any plan, they must monitor their progress towards their goals by regularly making metacognitive judgements about the past, pres­ ent and future state of their learning 132, 133 . Such judge­ ments might include considering how challenging it will be to learn a particular set of material, how well material has been learned already or the accuracy of the answers generated during their retrieval practice. The accuracy of these judgements directly informs the decisions that learners make in regulating their learning 134. Such deci­ sions include pivoting to a different learning strategy, allocating more study time to one set of material relative to another or deciding to terminate study. Inaccurate decisions can be costly, bringing additional motivational and affective elements into the metacognitive process. The educational psychology perspective is quite useful for considering how cognitive and metacogni­ tive processes interact with motivational and affective processes. Theories of self­ regulated learning within this perspective include such components 129, 135,136 . Indeed, much research in educational psychology has focused on how learners regulate their motivation to enhance their willingness and effort to engage in a learning task when faced with challenges such as boredom or difficulty 137, 138 .

Forging connections between educational and cogni­ tive psychology around the motivational and affective aspects of learning strategy use is of increasing interest to researchers 115, 117,139,140 .

Although there is consensus among researchers about strategies that are effective for learning, there is little scientific knowledge about how to support learn­ ers in acquiring the metacognitive knowledge and skills needed to facilitate optimal strategy selection and use. According to the friction hypothesis, students naturally develop more effective strategies when they encounter challenges in their learning environments:

experiencing challenges leads to growth in learning 141.

Although learners become more sophisticated in their ability to regulate their own learning as they develop and go through schooling, evidence to support the fric­ tion hypothesis is mixed at best 142– 144 . It seems implau­ sible that students could acquire the necessary complex mental model to guide effective learning without formal instruction to complement personal experience 145, 146 . Session 1 (day 1) Session 2 (day 3) Session 3 (day 8) Session 4 (day 10) 0 1 2 3 4 5 6 Trials per item to reach criterion One correct recall in session 1 Three correct recalls in session 1 Fig. 5 | successive relearning results. Results from the study depicted in Fig.  4 (reF. 105). Recalling each term three times in the initial learning session resulted in increased efficiency in the subsequent relearning sessions. Copyright © 2011 by APA. Reproduced and adapted with permission from reF . 105.

0123456789();: www.nature.com/nrpsychol REVIEWS For example, despite the importance of tailoring learn­ ing plans to factors such as the nature of the test, little evidence indicates that learners adjust their plans to match the test in educational contexts 147, even though they sometimes do in laboratory contexts148.

In sum, the educational psychology perspective com­ plements the cognitive psychology perspective. The cog­ nitive psychology perspective focuses on the micro­ level aspects of metacognition that occur within a single learning episode, whereas the educational psycho­ logy perspective focuses on the macro­ level aspects of metacognition that occur across learning episodes.

Future work is needed to bridge these two perspec­ tives and examine how micro ­ level cognitive processes operate within macro­ level cognitive, motivational and affective processes across contexts. Uniting these two perspectives is critical to improving the metacognition of strategy planning and use.

Improving metacognition. Improving metacognition is a complex and challenging endeavour. From the cognitive psychology perspective, efforts to improve metacogni­ tion have focused on increasing learners’ awareness and use of effective learning strategies. From an educational psychology perspective, improving metacognition is conceptualized within a broader set of cognitive, moti­ vational and affective components, all of which are crit­ ical to effective strategy planning and use. Many learners have inaccurate beliefs about learning that could be resistant to change (box  1) . The process of facilitating the acquisition of an accurate mental model of effective learning is therefore more likely to be a process of con­ ceptual change 149 than of increasing the complexity of a generally accurate initial model 10.

Even after learners are made aware of effective learn­ ing strategies, they do not automatically endorse or use those strategies 150,151 . Although some studies show that students’ awareness of their own knowledge can be improved by directly experiencing spacing 16 and retrieval practice 152, awareness alone is not enough to produce lasting changes in learners’ beliefs and strategy use.

Neither is simple experience with any strategy sufficient to change learners’ behaviours 151. Even if learners know how to use a strategy, they are not likely to use it unless they believe that the strategy works for them. However, comprehensive interventions that involve direct instruc­ tion about effective learning strategies, along with the opportunity for students to practise these strategies over time in their own courses, can be effective 153.

Indeed, a comprehensive approach is needed to address the multiple factors that inhibit the develop ­ ment of metacognitive skills. The knowledge, belief, commitment and planning framework 154 contains four evidence­ based practical recommendations for educa­ tors who want to implement such an intervention at any level of education. First, the intervention should provide direct instruction about effective learning strategies and how to use them. Second, interventions should provide learners with experiences using those strategies (com­ bined with knowledge of the outcomes) that can increase their knowledge of, and belief in, the effectiveness of those strategies. Third, interventions should support learners to create a plan for implementing effective strat­ egies in their own learning. Finally, interventions should encourage learners to commit to their plan by reflecting on the benefits of using such strategies. The knowledge, belief, commitment and planning framework posits that all four components are necessary for an effective inter ­ vention. This multifaceted approach is critical to pro­ ducing a mental model of effective learning that enables eventual independence as well as generalization to new learning experiences. Much like the acquisition of any skill, learning to learn effectively takes time, practice, effort and support. Summary and future directions Research on the psychology of learning has revealed that spacing and retrieval practice reliably enhance learning. However, these strategies are underused by students, possibly due to metacognitive factors such as false beliefs about learning, lack of awareness of effec ­ tive learning strategies or the counter ­ intuitive nature of these strategies. Successful learning requires an effective ‘learning routine’ — knowledge of the right strategies at the right times — as well as regular use of that routine. Learners Box 1 | False beliefs about learning Learners hold numerous inaccurate beliefs about learning. these beliefs can be studied directly by collecting learners’ opinions about the effectiveness of specific learning strategies. For example, when given a scenario describing spacing (compared with massing) and retrieval practice (compared with restudying) and asked which strategy would be more effective for learning, undergraduate students tend to choose the less effective strategies of massing and restudying 225. although spacing works for various learning materials, learners take into account the difficulty of the material and are more likely to prefer massing when they anticipate taking an easy test 150.

More broadly, the effort involved in a learning strategy might influence learners’ beliefs about that strategy. strategies such as repeatedly re- reading and highlighting tend to increase the feeling of fluency or ease with which materials are processed, and learners mistake this fluency as an indication that the materials have been well learned 132, 226 . this ‘illusion of learning’ could be part of why students tend to overuse ineffective strategies 116, 122,125,227 even though they are a poor predictor of academic success 228. students also endorse other situations that minimize the appearance of effort and difficulty — such as a lecture delivered in a smooth and well- polished man - ner or a lecture compared with active problem- solving activities — as more effective for their learning, although the opposite is true 132, 226,229 .

By contrast, effective learning strategies such as spacing and retrieval (along with other potentially effective strategies such as interleaving 230 and pre- questions 231) involve effort and a greater likelihood of making errors. However, learners believe that strate - gies involving effort are less effective for learning 91. even after directly experiencing spacing and retrieval in their own learning, learners rated these strategies as less effective than massing and re- reading, respectively 232. Learners also rated spacing and retrieval as more effortful, and ratings of effort negatively predicted perceived effective - ness of the strategies and willingness to use them. thus, students tend to misinterpret effort as a sign of ineffective learning 232 or the inability to succeed 233. this misperception matters because learners’ beliefs about the effectiveness of strategies are related to the use of those strategies 117, 234,235 . For instance, these false beliefs could underlie students’ tendencies to avoid learning situations that involve effort 232 and errors 236.

False beliefs about learning could originate from various sources, including learners’ intuitions, experiences and even formal education. such beliefs are not easily and immediately changed through simple interventions such as a one- time demonstration of an effective learning strategy 39, 170 . However, learners can acquire more accurate beliefs about learning through comprehensive interventions that involve direct instruc - tion on the research supporting effective learning strategies and how to use them, combined with continued use of those strategies over time and experience with the outcomes 153.

0123456789();: NATURE REVIEWS | PSYCHOLOGY REVIEWs can be aware of what is needed for effective learning but fail to achieve their learning goals if they do not carry out an effective routine. Thus, a top priority for future research is to understand the decisions and actions that learners take during learning, including their use (or misuse) of effective learning strategies and the fac­ tors that hinder or facilitate use of these strategies. The motivational and affective influences on these decisions are particularly important in real learning situations, highlighting the need for more studies investigating how these factors contribute to learners’ decisions and actions. Furthermore, future research can bring critical new insights by broadening the approach to understand­ ing how complex mental models of learning are devel­ oped, through exploring the contributions of various cognitive and non ­ cognitive factors (including social, motivational and affective aspects) to self­ regulated learning in real situations. Technology is likely to play a key role in future research on learning. New technology makes it possible to collect large quantities of data quickly, opening up possibilities for the analysis of comprehensive datasets that include information about students (for example, demographic information and prior knowledge), their learning behaviours and decisions, and the learning context. For instance, online course management systems can collect data on the effectiveness of particular strategies (such as online quizzes) and student characteristics, which can together answer how course­ related and student­ related factors interact to predict learning. Technological advances also enable new research questions, such as determining the effectiveness of quizzes that are adapted to the learner’s performance. Digital tools can also make it easier to implement learning activities and evaluate the effectiveness of learning strategies in ways that have not yet been widely and systematically explored, such as using mobile devices to deliver practice quizzes outside class 155.

Finally, an important question for future research is how to effectively enhance skills in critical thinking.

In an age when information is widely available but not always accurate 156– 159 , one of the most valuable skills a learner can have is the ability to critically evaluate infor ­ mation. Effective learning strategies such as spacing can enhance skills in critical thinking and evaluating the credibility of information 18. More research can shed additional light on the best strategies and approaches for building these skills. Critical thinking skills will be especially important for learners in an educational land­ scape that is becoming increasingly flexible and depend­ ent upon learners to initiate and regulate the actions that are best for their own learning. Published online xx xx xxxx Factors influencing updating of knowledge or beliefs • Current and prior experience with the task • Attributions about success or failure • Strength of existing knowledge and beliefs Factors influencing task evalution • Task instructions • Content and structure of materials • Modality of materials (text or video) • Nature of future assessment or use Factors influencing strategy selection • Learning goal • Knowledge and beliefs about:

• Learning processes • Task • Strategy effectiveness • Guidance from instructors Factors influencing monitoring • Utilization of metacognitive cues • Subjective difficulty of task • Beliefs about what difficulty signals • Performance in self-testing Factors influencing reflection on learning outcome • Initial learning goal • Task performance • Degree of success or failure • Feedback Update knowledge or beliefs Evaluate learning task Select and use strategies Reflect on learning outcome Monitor learning Fig. 6 | common factors influencing the metacognition of strategy use. Metacognition of strategy use is conceptual- ized as a cyclical process influenced by various factors at each stage. The factors specified are not intended to be an exhaustive list (for example, learners’ motivation and affect can influence strategy use at multiple stages) but are examples to illustrate the complex nature of the metacognitive processes involved in strategy use. 1 . Witherby, A. E. & Tauber, S. K. The current status of students’ note- taking: why and how do students take notes? J. Appl. Res. Mem. Cogn. 8, 139–153 (2019).

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Learning from errors: students’ and instructors’ practices, attitudes, and beliefs. Memory 28, 1105–1122 (2020). AcknowledgementsThis material is based upon work supported by the James S.

McDonnell Foundation 21st Century Science Initiative in Understanding Human Cognition, Collaborative Grant 220020483. The authors thank C. Phua for assistance with verifying references. Author contributionsAll authors contributed to the design of the article. S.K.C.

drafted the sections on measuring learning, spacing, succes- sive relearning and future directions; S.C.P. drafted the sec - tion on retrieval practice, developed the figures and drafted the tables; A.C.B. drafted the section on metacognition. All authors edited and approved the final draft of the complete manuscript.

Competing interestsThe authors declare no competing interests.

Peer review informationNature Reviews Psychology thanks Veronica Yan, who co- reviewed with Brendan Schuetze; Mirjam Ebersbach; and Nate Kornell for their contribution to the peer review of this work.

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