Adolescent Development

The conventional view of brain development has been that most of this takes place in utero and in the first three years, with the further development continuing until the brain is fully mature at around 10-12 years of age. The turbulence of adolescent behavior has been deemed to be mostly caused by hormonal changes. Piaget, who identified four stages of cognitive development, assessed that his highest stage — that of formal, abstract reasoning — occurred around 13-14 years (although not everyone reaches this level, which requires appropriate education).

Recent studies, however, are painting a different picture. Evidence is converging that the brain continues to grow and develop throughout the teen years, and possibly even into the early twenties. Indeed, early adolescence appears to be a time of significant growth and development.

The vulnerability of the adolescent brain to drugs and alcohol is well-established. The picture that is now emerging is that adolescence is a time of heightened vulnerability partly because different systems are maturing according to different timetables — adolescence is a time when brain systems are out-of-sync, as it were. Adolescence is increasingly seen as a critical period for a reorganization of regulatory systems. This reorganization is both hazardous and an opportunity.

Adolescence, then, is rightly seen as a time when we take our first steps on the path we will take through adulthood. But this cliché has a deeper meaning than we ever suspected. For one thing, an important part of brain development during adolescence concerns the pruning of unused neurons and connections, resulting in a strengthening of those connections that are most used. In other words, it’s a time to lose the things we don’t care about, and strengthen those we do.

Much of this process seems to occur in the frontal cortex, where our “higher” faculties, such as decision-making, goal-setting, and executive control, reside. Maturation of the brain seems to occur roughly from the back to the front: the cerebellum (involved in motor skills) is the first to mature, and the prefrontal cortex the last (possibly not until the mid-twenties).

Poor decision-making, reckless behavior, rule breaking, the tendency toward emotional outbursts, fewer organizational abilities, and lack of ability to process abstract concepts have all been associated with problems in pruning. The ability to multi-task continues to develop until ages 16-17. The delay in maturation of the prefrontal cortex has also been implicated in difficulties in reading emotional cues, which in turn has implications for teens’ ability to communicate with others.

In other words, we as adults may often expect too much from teenagers. We need to keep these cognitive limitations in mind, particularly when teens are confronting with demanding situations. Truly it has been said, the teenage brain is a work in progress, not a finished product.


  • Herrmann, J.W. 2005.The Teen Brain as a Work in Progress: Implications for Pediatric Nurses. Pediatric Nursing, 31 (2), 144-148.
  • Luciana, M., Conklin, H.M., Hooper, C.J. & Yarger, R.S. 2005. The development of nonverbal working memory and executive control processes in adolescents. Child Development, 76(3),
  • Steinberg, L. 2005. Cognitive and affective development in adolescence. Trends in Cognitive Sciences, 9 (2), 69-74.

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Each hour of screen time linked to poorer grades

  • A large study found teenagers' grades suffered significantly and linearly, for each hour spent watching TV, using the internet or playing computer games.
  • Of these activities, the most harmful was watching TV.
  • Hours spent doing homework or reading for pleasure were each associated with a significant increase in GCSE grades.
  • The amount of moderate-to-vigorous physical activity had no effect on grades.

A study involving 845 secondary school students has revealed that each hour per day spent watching TV, using the internet or playing computer games at average age 14.5 years was associated with poorer GCSE grades at age 16. Additionally, each hour of daily homework and reading was linked to significantly better grades. Surprisingly, however, the amount of physical activity had no effect on academic performance.

Median screen time was four hours a day, of which around half was spent watching TV; median sedentary non-screen time (reading/homework) was 1.5 hours.

Each hour per day of time spent in front of the TV or computer in Year 10 was associated with 9.3 fewer GCSE points in Year 11 — the equivalent to two grades in one subject or one grade in each of two subjects. Two hours was therefore associated with 18 fewer points at GCSE, and the median of four hours, with a worrying 36 fewer points.

The burning question: are some screens better than others? Comparison of the different screen activities revealed that TV viewing was the most detrimental to grades.

More positively, each hour of daily homework and reading was associated with an average 23.1 more GCSE points. This was a U-shaped function, however, with pupils doing over four hours of reading or homework a day performing less well than their peers. But the number of pupils in this category was relatively low (only 52 pupils) and may include students who were struggling at school.

The benefits from spending time on homework or reading were not simply a consequence of spending less time staring at a screen; screen time and time spent reading or doing homework were independently associated with academic performance.

Do note that, although some homework was doubtless done on the computer, this was not counted as screen time for the purposes of this study.

The finding of no significant association between moderate to vigorous physical activity and academic performance is more surprising, given the evidence for the benefits of exercise and physical fitness for cognition. The median was 39 minutes of moderate to vigorous physical activity a day, with a quarter of the students getting less than 20 minutes a day, and a quarter getting more than 65 minutes.

The data used was from the ROOTS study, a large longitudinal study assessing health and wellbeing during adolescence. Objective levels of activity and time spent sitting were assessed through a combination of heart rate and movement sensing. Screen time, time spent doing homework, and reading for pleasure, relied on self-report. Medians were used rather than means, because of the degree of skew in the data.



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Music training in adolescence improves auditory & language skills

We've seen a number of studies showing the value of music training for children's development of language skills. A new study has investigated what happens if the training doesn't begin until high school.

The study involved 40 Chicago-area high school students who were followed from their beginning at high school until their senior year. Nearly half the students had enrolled in band classes, which involved two to three hours a week of instrumental group music instruction in school. The rest had enrolled in junior Reserve Officers' Training Corps (ROTC), which emphasized fitness exercises during a comparable period.

The music group showed more rapid maturation in the brain's response to sound, and demonstrated prolonged heightened brain sensitivity to sound details. While all students improved in language skills tied to sound-structure awareness, the improvement was greater for those in music classes.

The finding is encouraging in that it shows that adolescent brains are still receptive to music training.

It's also encouraging in involving students from low-income areas. Children from families of lower socioeconomic status have been found to process sound less efficiently, in part because of noisier environments and also due to linguistic deprivation. A previous small study by the same researchers looked at the benefits of a free community music program for a group of disadvantaged students (the Harmony Project). In this small study, students more engaged in the program (as assessed by attendance and participation) showed greater improvement after two years, in how their brains processed speech and in their reading scores. Those who learned to play instruments also showed greater improvement than those who participated in music appreciation classes.



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Short online ‘pep talks’ can boost students

A large study shows how a 45-minute online intervention can improve struggling high school students' attitude to schoolwork, and thus their academic performance.

There's been a lot of talk in recent years about the importance of mindset in learning, with those who have a “growth mindset” (ie believe that intelligence can be developed) being more academically successful than those who believe that intelligence is a fixed attribute. A new study shows that a 45-minute online intervention can help struggling high school students.

The study involved 1,594 students in 13 U.S. high schools. They were randomly allocated to one of three intervention groups or the control group. The intervention groups either experienced an online program designed to develop a growth mindset, or an online program designed to foster a sense of purpose, or both programs (2 weeks apart). All interventions were expected to improve academic performance, especially in struggling students.

The interventions had no significant benefits for students who were doing okay, but were of significant benefit for those who had an initial GPA of 2 or less, or had failed at least one core subject (this group contained 519 students; a third of the total participants). For this group, each of the interventions was of similar benefit; interestingly, the combined intervention was less beneficial than either single intervention. It's plausibly suggested that this might be because the different messages weren't integrated, and students may have had some trouble in taking on board two separate messages.

Overall, for this group of students, semester grade point averages improved in core academic courses and the rate at which students performed satisfactorily in core courses increased by 6.4%.

GPA average in core subjects (math, English, science, social studies) was calculated at the end of the semester before the interventions, and at the end of the semester after the interventions. Brief questions before and after the interventions assessed the students' beliefs about intelligence, and their sense of meaningfulness about schoolwork.

GPA before intervention was positively associated with a growth mindset and a sense of purpose, explaining why the interventions had no effect on better students. Only the growth mindset intervention led to a more malleable view of intelligence; only the sense-of-purpose intervention led to a change in perception in the value of mundane academic tasks. Note that the combined intervention showed no such effects, suggesting that it had confused rather than enlightened!

In the growth mindset intervention, students read an article describing the brain’s ability to grow and reorganize itself as a consequence of hard work and good strategies. The message that difficulties don't indicate limited ability but rather provide learning opportunities, was reinforced in two writing exercises. The control group read similar materials, but with a focus on functional localization in the brain rather than its malleability.

In the sense-of-purpose interventions, students were asked to write about how they wished the world could be a better place. They read about the reasons why some students worked hard, such as “to make their families proud”; “to be a good example”; “to make a positive impact on the world”. They were then asked to think about their own goals and how school could help them achieve those objectives. The control group completed one of two modules that didn't differ in impact. In one, students described how their lives were different in high school compared to before. The other was much more similar to the intervention, except that the emphasis was on economic self-interest rather than social contribution.

The findings are interesting in showing that you can help poor learners with a simple intervention, but perhaps even more, for their indication that such interventions are best done in a more holistic and contextual way. A more integrated message would hopefully have been more effective, and surely ongoing reinforcement in the classroom would make an even bigger difference.




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Older news items (pre-2010) brought over from the old website

Aerobic fitness boosts IQ in teenage boys

Data from the 1.2 million Swedish men born between 1950 and 1976 who enlisted for mandatory military service at the age of 18 has revealed that on every measure of cognitive performance, average test scores increased according to aerobic fitness — but not muscle strength. The link was strongest for logical thinking and verbal comprehension, and the association was restricted to cardiovascular fitness. The results of the study also underline the importance of getting healthier between the ages of 15 and 18 while the brain is still changing — those who improved their cardiovascular health between 15 and 18 showed significantly greater intelligence scores than those who became less healthy over the same time period. Those who were fittest at 18 were also more likely to go to college. Although association doesn’t prove cause, the fact that the association was only with cardiovascular fitness and not strength supports a cardiovascular effect on brain function. Results from over 260,000 full-sibling pairs, over 3,000 sets of twins, and more than 1,400 sets of identical twins, also supports a causal relationship.

[1486] Åberg MAI, Pedersen NL, Torén K, Svartengren M, Bäckstrand B, Johnsson T, Cooper-Kuhn CM, Åberg DN, Nilsson M, Kuhn GH. Cardiovascular fitness is associated with cognition in young adulthood. Proceedings of the National Academy of Sciences [Internet]. 2009 ;106(49):20906 - 20911. Available from:

Amphetamine use in adolescence may impair adult working memory

Rats exposed to high doses of amphetamines at an age that corresponds to the later years of human adolescence showed significant declines in working memory as adults, long after the exposure. The researchers tested two types of amphetamine exposure: intermittent (a steady dose every other day) and "binge-escalation," in which increasing amounts of the drug were given over a period of four days, followed by a simulated binge – a high dose every two hours for eight hours on the fifth day. The type of exposure did not make a significant difference.

Stanis, J.J. et al. 2009. Amphetamine-induced deficits in a working memory task are more significant in drug-exposed adolescent rats than drug-exposed adults. Presented October 21 at the annual meeting of the Society for Neuroscience in Chicago.

Linking education to future goals may boost grades more than helping with homework

A review of 50 studies looking at what kinds of parent involvement helps children's academic achievement has revealed that the most important thing parents can do for their middle school children (early adolescence) is relate academic achievement to future job goals, and give advice on specific study strategies. Parents' involvement in school events also had a positive effect, but a smaller one. Helping with homework had mixed results.

Hill, N.E. & Tyson, D.F. 2009. Parental Involvement in Middle School: A Meta-Analytic Assessment of the Strategies That Promote Achievement. Developmental Psychology, 45 (3), 740-763.

Adolescent binge drinking may compromise white matter

An imaging study of 28 teens, of whom half had a history of binge drinking (but did not meet the criteria for alcohol abuse), has found that those who had engaged in binge drinking episodes had lower coherence of white matter fibers in 18 different areas across the brain. The findings add to a growing literature indicating that adolescent alcohol involvement is associated with specific brain characteristics. White matter integrity is essential to the efficient relay of information in the brain.

[1426] McQueeny T, Schweinsburg BC, Schweinsburg AD, Jacobus J, Bava S, Frank LR, Tapert SF. Altered white matter integrity in adolescent binge drinkers. Alcoholism, Clinical and Experimental Research [Internet]. 2009 ;33(7):1278 - 1285. Available from:

Childhood sleep problems persisting through adolescence may affect cognitive abilities

A longitudinal study involving 916 twins whose parents reported their children's sleep problems from age 4 until 16, of whom 568 completed tests of executive functioning at 17, indicates that those whose sleep problems persisted through adolescence had poorer executive functioning at age 17 than children whose problems decreased to a greater extent. Sleep problems as early as age 9, but particularly around age 13, showed significant associations with later executive functions. Some problems appear to be more important than others: changes in levels of 'sleeping more than other children' and 'being overtired' were most important, and nightmares and 'trouble sleeping' the least. However, a child's level of sleep problems early in life don’t appear to be an important factor.

[930] Friedman NP, Corley RP, Hewitt JK, Wright KP. Individual Differences in Childhood Sleep Problems Predict Later Cognitive Executive Control. Sleep. 2009 ;32(3):323 - 333.

From 12 years onward you learn differently

Behavioral studies have found eight-year-olds learn primarily from positive feedback, with negative feedback having little effect. Twelve-year-olds, however, are better able to process negative feedback, and use it to learn from their mistakes. Now brain imaging reveals that the brain regions responsible for cognitive control (specifically, the dorsolateral prefrontal cortex and superior parietal cortex, and the pre-supplementary motor area/anterior cingulate cortex) react strongly to positive feedback and scarcely respond at all to negative feedback in children of eight and nine, but the opposite is the case in children of 11 to 13 years, and also in adults.

van Duijvenvoorde, A.C.K. et al. 2008. Evaluating the Negative or Valuing the Positive? Neural Mechanisms Supporting Feedback-Based Learning across Development. The Journal of Neuroscience, 28, 9495-9503.

Frequent TV viewing during adolescence linked with risk of attention and learning difficulties

A long-running study of 678 families in upstate New York, surveyed children at 14, 16 and 22 years old (averages), and again when the children in the study had reached an average age of 33. At age 14, 225 (33.2%) of the teens reported that they watched three or more hours of television per day. Those who watched 1 or more hours of television per day at mean age 14 years were at higher risk of poor homework completion, negative attitudes toward school, poor grades, and long-term academic failure. Those who watched 3 or more hours of television per day were most likely to experience these outcomes, and moreover were at higher risk of subsequent attention problems and were the least likely to receive postsecondary education. Analysis of the data also indicated that television watching contributes to learning difficulties and not vice versa.

Johnson, J.G., Cohen, P., Kasen, S. & Brook, J.S. 2007. Extensive Television Viewing and the Development of Attention and Learning Difficulties During Adolescence. Archives of Pediatrics & Adolescent Medicine, 161 (5), 480-486.

Prefrontal cortex loses neurons during adolescence

A rat study has found that adolescents lose neurons in the ventral prefrontal cortex in adolescence, with females losing about 13% more neurons than males. Human studies have found gradual reductions in the volume of gray matter in the prefrontal cortex from adolescence to adulthood, but this finding that neurons are actually dying is new, and indicates that the brain reorganizes in a very fundamental way in adolescence. The number of neurons in the dorsal prefrontal cortex didn’t change, although the number of glial cells increased there (while remaining stable in the ventral area). The finding could have implications for understanding disorders that often arise in late adolescence, such as schizophrenia and depression, and why addictions that start in adolescence are harder to overcome than those that begin in adulthood.

Markham, J.A., Morris, J.R. & Juraska, J.M. 2007. Neuron number decreases in the rat ventral, but not dorsal, medial prefrontal cortex between adolescence and adulthood. Neuroscience, 144 (3), 961-968.

Brain still developing at age 18

In a study of 19 freshman college students, it’s been found that, anatomically, significant changes in brain structure continue after age 18. The changes were localized to regions of the brain known to integrate emotion and cognition — specifically, areas that take information from our current body state and apply it for use in navigating the world (right midcingulate, inferior anterior cingulate gyrus, right caudate head, right posterior insula, and bilateral claustrum).

Bennett, C.M. & Baird, A.A. 2006. Anatomical changes in the emerging adult brain: A voxel-based morphometry study. Human Brain Mapping, Article published online 29 Nov 2005 in advance of print./span>

Study links adolescent IQ/activity levels with risk of dementia

An analysis of high school records and yearbooks from the mid-1940s, and interviews with some 400 of these graduates, now in their 70s, and their family members, has found that those who were more active in high school and who had higher IQ scores, were less likely to have mild memory and thinking problems and dementia as older adults.

Fritsch, T., Smyth, K.A., McClendon, M.J., Ogrocki, P.K., Santillan, C., Larsen, J.D. & Strauss, M.E. 2005. Associations Between Dementia/Mild Cognitive Impairment and Cognitive Performance and Activity Levels in Youth. Journal of the American Geriatrics Society, 53(7), 1191.

Teen's ability to multi-task develops late in adolescence

A study involving adolescents between 9 and 20 years old has found that the ability to multi-task continues to develop through adolescence. The ability to use recall-guided action to remember single pieces of spatial information (such as looking at the location of a dot on a computer screen, then, after a delay, indicating where the dot had been) developed until ages 11 to 12, while the ability to remember multiple units of information in the correct sequence developed until ages 13 to 15. Tasks in which participants had to search for hidden items in a manner requiring a high level of multi-tasking and strategic thinking continued to develop until ages 16 to 17. "These findings have important implications for parents and teachers who might expect too much in the way of strategic or self-organized thinking, especially from older teenagers."

[547] Luciana M, Conklin HM, Hooper CJ, Yarger RS. The Development of Nonverbal Working Memory and Executive Control Processes in Adolescents. Child Development. 2005 ;76(3):697 - 712.

The best way to get teens to learn

A recent study has been investigating how to motivate teenagers to learn. Using obese and non-obese early adolescents and a text on health-related issues, researchers found that telling the teenagers that learning more about these issues and adopting a healthier lifestyle was important for their health (an intrinsic goal) was more effective than telling them that it would help them become more physically attractive and appealing (an extrinsic goal). They also found that trying to pressure the teens by using guilt-inducing language was less effective than a more autonomy-supportive approach that enabled them to experience their studying as more self-chosen and volitional.

Vansteenkiste, M., Simons, J., Lens, W., Soenens, B. & Matos, L. 2005. Examining The Impact Of Extrinsic Vs. Intrinsic Goal Framing And Internally Controlling Vs. Autonomy-Supportive Communication Style Upon Children's Achievement. Child Development, 76 (2), 483-501.

Smoking associated with working memory impairment in adolescents

A study of 41 adolescent daily smokers and 32 nonsmokers has revealed that adolescent smokers had impairments in accuracy of working memory performance. Male adolescents as a group begin smoking at an earlier age than female smokers and were significantly more impaired during tests of selective and divided attention. All of the adolescent smokers also showed further disruption of working memory when they stopped smoking.

[1252] Jacobsen LK, Krystal JH, Mencl EW, Westerveld M, Frost SJ, Pugh KR. Effects of smoking and smoking abstinence on cognition in adolescent tobacco smokers. Biological Psychiatry [Internet]. 2005 ;57(1):56 - 66. Available from:

Alcohol's damaging effects on adolescent brain function

A number of speakers at Symposium speakers at the June 2004 Research Society on Alcoholism meeting in Vancouver, reported on research concerning the vulnerability of the adolescent brain to the damaging effects of alcohol. Some of the findings presented were:

  • The adolescent brain is more vulnerable than the adult brain to disruption from activities such as binge drinking. Adolescent rats that were exposed to binge drinking appear to have permanent damage in their adult brains.
  • Subtle but important brain changes occur among adolescents with Alcohol Use Disorder, resulting in a decreased ability in problem solving, verbal and non-verbal retrieval, visuospatial skills, and working memory.
  • The association between antisocial behavior during adolescence and alcoholism may be explained by abnormalities in the frontal limbic system, which appears to cause "blunted emotional reactivity".
  • Alcohol-induced memory impairments, such as "blackouts", are particularly common among young drinkers and may be at least in part due to disrupted neural plasticity in the hippocampus, which is centrally involved in the formation of autobiographical memories.

[1238] Monti PM, Miranda, Jr R, Nixon K, Sher KJ, Swartzwelder SH, Tapert SF, White A, Crews FT. Adolescence: Booze, Brains, and Behavior. Alcoholism: Clinical and Experimental Research [Internet]. 2005 ;29(2):207 - 220. Available from:

Changes in the brain during adolescence

A study of the post-mortem cerebral cortexes of six 12- to 17-year-olds and five 17- to 24-year-olds has revealed a number of physical differences between the adolescent and the adult brain. The average pyramidal soma size was 15.5 % smaller in the older age group, while a number of other measures (including cortical thickness and neural density) were slightly larger. These changes are thought to reflect certain cognitive changes that occur during adolescence - specifically, the increase in knowledge and understanding, and the decrease in the ability to acquire new sounds and speech patterns.

Courten-Myers, G.M. 2002. Paper presented at the American Academy of Neurology 54th Annual Meeting in Denver, Colorado, on April 19.

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No evidence of Alzheimer’s pathology in younger carriers of Alzheimer’s gene

Two studies indicate that young people carrying the “Alzheimer’s gene” (ApoE4) do not have the pathological changes found later in life. The first study, involving 1412 adolescents, found no differences in hippocampal volume or asymmetry as a function of gene status. The second study, involving 173 young adults (average age, 28 ± 7.6 years), found no difference in plasma concentrations of amyloid-beta peptides.


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Cognitive problems common in young people with MS

A study involving 187 children and adolescents with multiple sclerosis, plus 44 who experienced their first neurologic episode (clinically isolated syndrome) indicative of MS, has found that 35% of those with MS and 18% of those with clinically isolated syndrome were cognitively impaired. Cognitive assessment was done using a battery of 11 tests. The most common areas of impairment were fine motor coordination, visual-motor integration, and speeded information processing.



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Concussions in high school athletes may need longer recovery & better testing

February, 2013

Two small studies suggest that standard testing of concussed high school athletes might be insufficiently sensitive.

I’ve talked before about how even mild head injuries can have serious consequences, and in recent years we’ve seen growing awareness of the long-term dangers of sports’ concussions (especially for young people). This has been followed by a number of initiatives to help protect athletes. However, while encouraging, they may still be under-estimating the problem. Two recent studies, involving high school athletes who had experienced concussions, point to quite subtle impairment lasting for longer than expected.

In one study, 20 concussed adolescents were tested on their attention and executive function within 72 hours post injury, and then again at one week, two weeks, one month, and two months post injury. Compared with matched controls, they had a significantly greater switch cost on the Task-Switching Test and a significantly greater reaction time for the Attentional Network Test conflict effect component, with this lasting up to two months after injury.

The results suggest that longer recovery periods than the standard 7-10 days may be warranted, given that the slower reaction times (although only a matter of milliseconds) might make further injury more likely.

In another study, 54 adolescent athletes who had been concussed but who reported being symptom-free and had returned to baseline neurocognitive-test levels, were given, further testing. This revealed that over a quarter of them (27.7%) showed cognitive impairment following moderate physical exertion (15 to 25 minutes on a treadmill, elliptical, or stationary bicycle). These athletes scored significantly lower on verbal and visual memory, although processing speed and reaction was not affected (suggesting that tests focusing mainly on these latter abilities are insufficient).

The group affected did not differ from the rest in terms of symptoms or concussion history.

The findings suggest that computerized neurocognitive testing following moderate exertion should be part of the standard procedure when making return-to-play decisions.



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The role of motivation on academic performance

January, 2013

A study shows how easily you can affect motivation, producing a significant effect on college test scores, while a large German study finds that motivational and strategy factors, but not intelligence, affects growth in math achievement at high school.

I’ve spoken before about the effects of motivation on test performance. This is displayed in a fascinating study by researchers at the Educational Testing Service, who gave one of their widely-used tests (the ETS Proficiency Profile, short form, plus essay) to 757 students from three institutions: a research university, a master's institution and a community college. Here’s the good bit: students were randomly assigned to groups, each given a different consent form. In the control condition, students were told: “Your answers on the tests and the survey will be used only for research purposes and will not be disclosed to anyone except the research team.” In the “Institutional” condition, the rider was added: “However, your test scores will be averaged with all other students taking the test at your college.” While in the “Personal” condition, they were told instead: “However, your test scores may be released to faculty in your college or to potential employers to evaluate your academic ability.”

No prizes for guessing which of these was more motivating!

Students in the “personal” group performed significantly and consistently better than those in the control group at all three institutions. On the multi-choice part of the test, the personal group performed on average .41 of the standard deviation higher than the control group, and the institutional group performed on average .26 SD higher than the controls. The largest difference was .68 SD. On the essay, the largest effect size was .59 SD. (The reason for the results being reported this way is because the focus of the study was on the use of such tests to assess and compare learning gains by colleges.)

The effect is perhaps less dramatic at the individual level, with the average sophomore score on the multichoice test being 460, compared to 458 and 455, for personal, institutional, and control groups, respectively. Interestingly, this effect was greater at the senior level: 469 vs 466 vs 460. For the essay question, however, the effect was larger: 4.55 vs 4.35 vs 4.21 (sophomore); 4.75 vs 4.37 vs 4.37 (senior). (Note that these scores have been adjusted by college admission scores).

Students also reported on motivation level, and this was found to be a significant predictor of test performance, after controlling for SAT or placement scores.

Student participants had received at least one year of college, or (for community colleges) taken at least three courses.

The findings confirm recently expressed concern that students don’t put their best efforts into low-stakes tests, and that, when such tests are used to make judgments about institutional performance (how much value they add), they may well be significantly misleading, if different institutions are providing different levels of motivation.

On a personal level, of course, the findings may be taken as further confirmation of the importance of non-academic factors in academic achievement. Something looked at more directly in the next study.

Motivation, study habits—not IQ—determine growth in math achievement

Data from a large German longitudinal study assessing math ability in adolescents found that, although intelligence was strongly linked to students' math achievement, this was only in the initial development of competence. The significant predictors of growth in math achievement, however, were motivation and study skills.

Specifically (and excitingly for me, since it supports some of my recurring themes!), at the end of Grade 5, perceived control was a significant positive predictor for growth, and surface learning strategies were a significant negative predictor. ‘Perceived control’ reflects the student’s belief that their grades are under their control, that their efforts matter. ‘Surface learning strategies’ reflect the use of rote memorization/rehearsal strategies rather than ones that encourage understanding. (This is not to say, of course, that these strategies don’t have their place — but they need to be used appropriately).

At the end of Grade 7, however, a slightly different pattern emerged, with intrinsic motivation and deep learning strategies the significant positive predictors of growth, while perceived control and surface learning strategies were no longer significant.

In other words, while intelligence didn’t predict growth at either point, the particular motivational and strategy variables that affected growth were different at different points in time, reflecting, presumably, developmental changes and/or changes in academic demands.

Note that this is not to say that intelligence doesn’t affect math achievement! It is, indeed, a strong predictor — but through its effect on getting the student off to a good start (lifting the starting point) rather than having an ongoing benefit.

There was, sadly but unfortunately consistent with other research, an overall decline in motivation from grade 5 to 7. There was also a smaller decline in strategy use (any strategy! — presumably reflecting the declining motivation).

It’s also worth noting that (also sadly but unsurprisingly) the difference between school types increased over time, with those in the higher track schools making more progress than those in the lowest track.

The last point I want to emphasize is that extrinsic motivation only affected initial levels, not growth. The idea that extrinsic motivation (e.g., wanting good grades) is of only short-term benefit, while intrinsic motivation (e.g., being interested in the subject) is far more durable, is one I have made before, and one that all parents and teachers should pay attention to.

The study involved 3,520 students, following them from grades 5 to 10. The math achievement test was given at the end of each grade, while intelligence and self-reported motivation and strategy use were assessed at the end of grades 5 and 7. Intelligence was assessed using the nonverbal reasoning subtest of Thorndike’s Cognitive Abilities Test (German version). The 42 schools in the study were spread among the three school types: lower-track (Hauptschule), intermediate-track (Realschule), and higher-track (Gymnasium). These school types differ in entrance standards and academic demands.




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Alcohol and marijuana use in adolescence linked to impaired white-matter integrity

A brain-imaging study shows adolescents who abuse alcohol and marijuana show poorer white-matter integrity, with alcohol associated with continuing damage to wiring in prefrontal regions.

Chronic use of alcohol and marijuana during youth has been associated with poorer neural and cognitive function, which appears to continue into adulthood. A new study looking specifically at white-matter changes provides more support for the idea that adolescent brains may be at particular risk from the damage that substance abuse can bring.

The brain-imaging study compared 41 adolescents (aged 16-20) with extensive marijuana- and alcohol-use histories by mid-adolescence with 51 adolescents with no such history. The study found that substance users showed poorer white matter integrity in seven tracts (right and left superior longitudinal fasciculus, right posterior thalamic radiations, right prefrontal thalamic fibers, right superior temporal gyrus white matter, right inferior longitudinal fasciculus, left posterior corona radiata).

Two brain scans were taken, at baseline and at 18 months. Substance use interviews were given every six months.

More alcohol use during the interval was associated with worse integrity in both the right and left superior longitudinal fasciculi, above and beyond baseline values in these bundles. Marijuana use didn’t predict change over time. Those who had a history of more risk-taking behaviors showed poorer integrity of the right prefrontal thalamic fibers.

The findings add to previous research showing white matter problems in youth with substance-use histories. The study points to alcohol use during adolescence being particularly problematic. It also suggests that youth who engage in risk-taking behaviors may tend to have poorly developed fronto-thalamic tracts.

All of this is particularly worrying because it is thought that maturation of the brain during adolescence is the foundation for self-control, suggesting that substance abuse during this period may have long-lasting effects on the individual’s ability to plan, organize, and self-regulate.



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