Child Development

Children's cognitive development

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Untreated sleep apnea in children shrinks brain & may slow development

Brain scans of children who have moderate or severe obstructive sleep apnea have found significant reductions of gray matter across the brain.

The study compared brain scans from 16 children (aged 7-11) with obstructive sleep apnea to those from nine healthy children of the same age, gender, ethnicity and weight, who did not have apnea. The scans were also compared to 191 MRI scans of children who were part of an existing database.

The brains of those children with OSA showed reduced gray matter in multiple brain regions, including the frontal, prefrontal, and parietal cortices, temporal lobe, and the brainstem.

Sleep apnea is known to affect cognition in adults, but it may be that it is even more damaging in brains that are still developing. However, adult studies have also shown that treating sleep apnea reverses gray matter loss and improves cognition. This finding therefore emphasizes the importance of treating children's sleep apnea.

Sleep apnea affects up to 5% of all children (and we can only assume that this will get more common, if childhood obesity continues to rise).

Developing brain regions in children are hardest hit by sleep deprivation

Another study of sleep deprivation in children gives weight to the idea that it is particularly important for proper brain development that children get good sleep.

The study measured the brain activity in 13 healthy five to 12-year-olds as they slept. On the first occasion, the children went to bed at their normal bedtime; the second time, they stayed awake until late and thus received exactly half the normal amount of sleep.

The results indicate that children's brains respond to sleep deprivation differently than adults’ brains do. In adults, being deprived of sleep creates a greater need for deep sleep, which is manifested in greater slow-wave activation in the prefrontal cortex. In the children's brains, this slow-wave increase occurred in the back regions of the brain, in the parietal and occipital lobes. This suggests that these areas might be especially vulnerable to sleep deprivation.

Moreover, this difference was linked to levels of myelin in part of the visual system. Myelin increases as the brain matures. Those with higher levels of myelin in certain nerve fibers in the visual system displayed slow-wave activation that was more similar to that of adults.

The researchers conclude that adequate sleep is important for neuronal connections to develop properly.

Poor sleep in early childhood may lead to cognitive, behavioral problems in later years

A study involving 1,046 children whose sleep was assessed at various points in their first seven years has found that children who didn’t get enough sleep in their preschool and early school years were more likely to have problems with attention, emotional control and peer relationships at age seven.

Sleep was assessed through interviews with the mothers when their children were around 6 months, 3 years and 7 years old, and from questionnaires completed when the children were ages 1, 2, 4, 5 and 6. Mothers and teachers filled out questionnaires evaluating each child's executive function and behavioral issues at around 7.

Children living in homes with lower household incomes and whose mothers had lower education levels were more likely to sleep less than nine hours at ages 5 to 7. Other factors associated with insufficient sleep include more television viewing, a higher body mass index, and being African American.

Insufficient sleep was defined as being less than the recommended amount of sleep at specific age categories:

  • 12 hours or longer at ages 6 months to 2 years
  • 11 hours or longer at ages 3 to 4 years
  • 10 hours or longer at 5 to 7 years.

https://www.eurekalert.org/pub_releases/2017-03/uocm-usa031517.php

https://www.eurekalert.org/pub_releases/2016-10/uoz-dbr100416.php

https://www.eurekalert.org/pub_releases/2016-11/f-hkb112816.php

https://www.eurekalert.org/pub_releases/2017-03/mgh-psi030917.php

A study involving 30 children (aged 8-10), of whom 15 had experienced a sports-related concussion two years earlier, and all of whom were athletically active, found that those with a history of concussion performed worse on tests of working memory, attention and impulse control, compared to the controls. This impaired performance was also reflected in differences in brain activity. Additionally, those who were injured at a younger age had the largest cognitive deficits.

All of this points to a need for focused and perhaps prolonged interventions, especially for younger children.

http://www.eurekalert.org/pub_releases/2015-12/uoia-scc121815.php

A small study involving 50 children and teens living in Mexico City (aged 13.4 ± 4.8 years) has found that those with the 'Alzheimer's gene' APOEε4 (22 of the 50) were more vulnerable to the effects of air pollution on cognition. Those with the gene variant had a reduced NAA/Cr ratio in the right frontal white matter (as those with Alzheimer's do), poorer attention and short-term memory, and below-average scores in Verbal and Full Scale IQ (>10 points), compared to those with the 'normal' ε3 variant. They also had problems with odor detection, also typical of those developing Alzheimer's.

The study is small and lacks a proper control group, but while other studies have found some signs of early brain differences in those carrying the ε4 variant, they have not been nearly as marked as this. The finding certainly warrants concern and further study.

http://www.eurekalert.org/pub_releases/2015-02/tuom-usf021115.php

http://www.eurekalert.org/pub_releases/2015-02/ip-dis020215.php

Calderón-Garcidueñas, L. et al. 2015. Decreases in Short Term Memory, IQ, and Altered Brain Metabolic Ratios in Urban Apolipoprotein ε4 Children Exposed to Air Pollution. Journal of Alzheimer's Disease, 45(3)

Following a previous study linking higher maternal levels of two common chemicals with slower mental and motor development in preschoolers, a new study has found that this effect continues into school age.

The study involved 328 inner-city mothers and their children. The mothers' levels of prenatal urinary metabolites of di-n-butyl phthalate (DnBP), butylbenzyl phthalate (BBzP), di-isobutyl phthalate (DiBP), di-2-ethylhexyl phthalate and diethyl phthalate were measured in late pregnancy. IQ tests were given to the children at age 7.

Children's IQ scores were negatively associated with higher maternal phthalate levels. Among children of mothers with the highest versus lowest levels of DnBP and DiBP metabolite concentrations (the top 25% vs the bottom 25%), IQ was 6.7 and 7.6 points lower, respectively. There were similar associations with processing speed, perceptual reasoning and working memory; DiBP and verbal comprehension; BBzP and perceptual reasoning.

DnBP and DiBP are found in a wide variety of consumer products, from dryer sheets to vinyl fabrics to personal care products like lipstick, hairspray, and nail polish, even some soaps. Since 2009, several phthalates have been banned from children's toys and other childcare articles in the United States.

Although the results are correlational, and don't prove that phthalates are responsible, the researchers recommend that pregnant women avoid storing or microwaving food in plastic containers, and avoid scented cleaning and personal care products (phthalates hold scent). They are also advised not to use plastics labeled 3, 6, or 7.

Factors such as maternal IQ, maternal education, and quality of the home environment, were controlled for in the analysis. The range of phthalate metabolite levels measured in the mothers was not unusual.

http://www.eurekalert.org/pub_releases/2014-12/cums-pet120414.php

http://www.theguardian.com/lifeandstyle/2014/dec/10/phthalates-damage-childrens-iqs-womb-plastic-chemicals

[3841] Factor-Litvak P, Insel B, Calafat AM, Liu X, Perera F, Rauh VA, Whyatt RM. Persistent Associations between Maternal Prenatal Exposure to Phthalates on Child IQ at Age 7 Years. PLoS ONE [Internet]. 2014 ;9(12). Available from: http://dx.doi.org/10.1371/journal.pone.0114003

A gene linked to Alzheimer's has been linked to brain changes in childhood. This gene, SORL1, has two connections to Alzheimer’s: it carries the code for the sortilin-like receptor, which is involved in recycling some molecules before they develop into amyloid-beta; it is also involved in lipid metabolism, putting it at the heart of the vascular risk pathway.

Brain imaging of 186 healthy individuals (aged 8-86) found that, even among the youngest, those with a specific variant of SORL1 showed a reduction in white matter connections. Post-mortem brain tissue from 269 individuals (aged 0-92) without Alzheimer's disease, found that the same SORL1 variant was linked to a disruption in the process by which the gene translated its code to become the sortilin-like receptor, and this was most prominent during childhood and adolescence. Another set of post-mortem brains from 710 individuals (aged 66-108), of whom the majority had mild cognitive impairment or Alzheimer's, found that the SORL1 risk gene was linked with the presence of amyloid-beta.

It may be that, for those carrying this gene variant, lifestyle interventions may be of greatest value early in life.

http://www.eurekalert.org/pub_releases/2013-12/cfaa-arg120313.php

[3570] Felsky D, Szeszko P, Yu L, Honer WG, De Jager PL, Schneider JA, Malhotra AK, Lencz T, Ikuta T, Pipitone J, et al. The SORL1 gene and convergent neural risk for Alzheimer’s disease across the human lifespan. Molecular Psychiatry [Internet]. 2013 . Available from: http://www.nature.com/mp/journal/vaop/ncurrent/full/mp2013142a.html

I recently discussed some of the implications of head injuries and how even mild concussions can have serious and long-term consequences. A follow-up study looking at the effects of childhood traumatic brain injury ten years after the event has found that even those with mild TBI showed some measurable effects, while those with severe TBI had markedly poorer performance on a number of cognitive measures.

The study involved 40 children who were admitted to hospital with TBI in early childhood (between 2 to 7 years; average just under 5), and 16 healthy controls. The children’s cognitive functions were assessed at the time of accident, and again at 12 and 30 months and 10 years later. Of the 40 with TBIs, 7 had mild injuries, 20 had moderate, and 13 severe.

Unsurprisingly, children with severe TBI had the poorest outcomes. This group was significantly poorer (compared to controls) on full scale IQ; performance IQ; verbal IQ; verbal comprehension; perceptual organization, processing speed. Those who had moderate TBI were significantly poorer on full scale IQ and verbal comprehension only, and those with mild TBI performed more poorly than the controls on verbal comprehension only. Note the size of these effects: the average scores of the group with severe TBI were 18-26 points lower than the control group. In comparison, those with moderate TBI were around 10 points lower on the two significant measures.

These findings are in contrast to research involving adults and older children, where IQ tends to remain intact.

They also contradict the belief that young brains have greater ability to ‘bounce back’ from injury.

Interestingly, the recovery trajectory wasn’t significantly affected by severity of injury — all the groups followed a similar pattern and they all tended to plateau from 5 to 10 years after injury. In general, the findings paint a picture of a long period of disrupted development immediately after the injury, lasting perhaps as long as 30 months, before the brain has recovered sufficiently to progress relatively normally. In other words, intervention may be helpful even years after the injury.

One weakness in the study is the small number of mild TBI cases. It should also be noted that the IQ of the control group was surprisingly high (113). However, given that they had similar IQ levels to the TBI groups prior to injury, it is possible that this reflects a practice effect (but remember that all groups got the same amount of practice).

One thing I wonder about, given recent research pointing to the value of schooling in raising IQ, is the extent to which some of this is due to loss of education that may have resulted from severe injury.

In the study, 18 children (aged 7-8), 20 adolescents (13-14), and 20 young adults (20-29) were shown pictures and asked to decide whether it was a new picture or one they had seen earlier. Some of the pictures were of known objects and others were fanciful figures (this was in order to measure the effects of novelty in general). After a 10-minute break, they resumed the task — with the twist that any pictures that had appeared in the first session should be judged “new” if that was the first appearance in the second session. EEG measurements (event-related potentials — ERPs) were taken during the sessions.

ERPs at the onset of a test stimulus (each picture) are different for new and old (repeated) stimuli. Previous studies have established various old/new effects that reflect item and source memory in adults. In the case of item memory, recognition is thought to be based on two processes — familiarity and recollection — which are reflected in ERPs of different timings and location (familiarity: mid-frontal at 300-500 msec; recollection: parietal at 400-70 msec). Familiarity is seen as a fast assessment of similarity, while recollection varies according to the amount of retrieved information.

Source memory appears to require control processes that involve the prefrontal cortex. Given that this region is the slowest to mature, it would not be surprising if source memory is a problematic memory task for the young. And indeed, previous research has found that children do have particular difficulty in sourcing memories when the sources are highly similar.

In the present study, children performed more poorly than adolescents and adults on both item memory and source memory. Adolescents performed more poorly than adults on item memory but not on source memory. Children performed more poorly on source memory than item memory, but adolescents and adults showed no difference between the two tasks.

All groups responded faster to new items than old, and ERP responses to general novelty were similar across the groups — although children showed a left-frontal focus that may reflect the transition from analytic to a more holistic processing approach.

ERPs to old items, however, showed a difference: for adults, they were especially pronounced at frontal sites, and occurred at around 350-450 msec; for children and adolescents they were most pronounced at posterior sites, occurring at 600-800 msec for children and 400-600 msec for adolescents. Only adults showed the early midfrontal response that is assumed to reflect familiarity processing. On the other hand, the late old/new effect occurring at parietal sites and thought to reflect recollection, was similar across all age groups. The early old/new effect seen in children and adolescents at central and parietal regions is thought to reflect early recollection.

In other words, only adults showed the brain responses typical of familiarity as well as recollection. Now, some research has found evidence of familiarity processing in children, so this shouldn’t be taken as proof against familiarity processing in the young. What seems most likely is that children are less likely to use such processing. Clearly the next step is to find out the factors that affect this.

Another interesting point is the early recollective response shown by children and adolescents. It’s speculated that these groups may have used more retrieval cues — conceptual as well as perceptual — that facilitated recollection. I’m reminded of a couple of studies I reported on some years ago, that found that young children were better than adults on a recognition task in some circumstances — because children were using a similarity-based process and adults a categorization-based one. In these cases, it had more to do with knowledge than development.

It’s also worth noting that, in adults, the recollective response was accentuated in the right-frontal area. This suggests that recollection was overlapping with post-retrieval monitoring. It’s speculated that adults’ greater use of familiarity produces a greater need for monitoring, because of the greater uncertainty.

What all this suggests is that preadolescent children are less able to strategically recollect source information, and that strategic recollection undergoes an important step in early adolescence that is probably related to improvements in cognitive control. But this process is still being refined in adolescents, in particular as regards monitoring and coping with uncertainty.

Interestingly, source memory is also one of the areas affected early in old age.

Failure to remember the source of a memory has many practical implications, in particular in the way it renders people more vulnerable to false memories.

Brain imaging data from 103 healthy people aged 5-32, each of whom was scanned at least twice, has demonstrated that wiring to the frontal lobe continues to develop after adolescence.

The brain scans focused on 10 major white matter tracts. Significant changes in white matter tracts occurred in the vast majority of children and early adolescents, and these changes were mostly complete by late adolescence for projection and commissural tracts (projection tracts project from the cortex to non-cortical areas, such as the senses and the muscles, or from the thalamus to the cortex; commissural tracts cross from one hemisphere to the other). But association tracts (which connect regions within the same hemisphere) kept developing after adolescence.

This was particularly so for the inferior and superior longitudinal and fronto-occipital fascicule (the inferior longitudinal fasciculus connects the temporal and occipital lobes; the superior longitudinal fasciculus connects the frontal lobe to the occipital lobe and parts of the temporal and parietal lobes). These frontal connections are needed for complex cognitive tasks such as inhibition, executive functioning, and attention.

The researchers speculated that this continuing development may be due to the many life experiences in young adulthood, such as pursing post-secondary education, starting a career, independence and developing new social and family relationships.

But this continuing development wasn’t seen in everyone. Indeed, in some people, there was evidence of reductions, rather than growth, in white matter integrity. It may be that this is connected with the development of psychiatric disorders that typically develop in adolescence or young adulthood — perhaps directly, or because such degradation increases vulnerability to other factors (e.g., to drug use). This is speculative at the moment, but it opens up a new avenue to research.

Childhood amnesia — our inability to remember almost everything that happened to us when very young — is always interesting. It’s not as simple as an inability to form long-term memories. Most adults can’t remember events earlier than 3-4 years (there is both individual and cultural variability), even though 2-year-olds are perfectly capable of remembering past events (side-note: memory durability increases from about a day to a year from age six months to two years). Additionally, research has shown that young children (6-8) can recall events that happened 4-6 years previously.

Given that the ability to form durable memories is in place, what governs which memories are retained? The earliest memories adults retain tend to be of events that have aroused emotions. Nothing surprising about that. More interesting is research suggesting that children can only describe memories of events using words they knew when the experience occurred — the study of young children (27, 33 or 39 months) found that, when asked about the experimental situation (involving a "magic shrinking machine") six months later, the children easily remembered how to operate the device, but were only able to describe the machine in words they knew when they first learned how to operate it.

Put another way this isn’t so surprising: our memories depend on how we encode them at the time. So two things may well be in play in early childhood amnesia: limited encoding abilities (influenced but not restricted to language) may mean the memories made are poor in quality (whatever that might mean); the development of encoding abilities means that later attempts to retrieve the memory may be far from matching the original memory. Or as one researcher put it, the format is different.

A new study about childhood amnesia looks at a different question: does the boundary move? 140 children (aged 4-13) were asked to describe their three earliest memories, and then asked again two years later (not all could provide as many as three early memories; the likelihood improved with age).

While more than a third of the 10- to 13-year-olds described the same memory as their very earliest on both occasions, children between 4 and 7 at the first interview showed very little overlap between the memories (only 2 of the 27 4-5 year-olds, and 3 of the 23 6-7 year-olds). There was a clear difference between the overlap seen in this youngest group (4-7) and the oldest (10-13), with the in-between group (8-9) being placed squarely between the two (20.7% compared to 10% and 36%).

Moreover, children under 8 at the first interview mostly had no overlap between any of the memories they provided at the two interviews, while those who were at least 8 years old did. For the oldest groups (10-13), more than half of all the memories they provided were the same.

The children were also given recall cues for memories they hadn’t spontaneously recalled. That is, they were told synopses of memories belonging to both their own earlier memories, and other children’s earlier memories. Almost all of the false memories were correctly rejected (the exceptions mostly occurred with the youngest group, those initially aged 4-5). However, the youngest children didn’t recognize over a third of their own memories, while almost all the oldest children’s memories were recognized (90% by 8-11 year-olds; all but one by 12-13 year-olds). Their age at the time of the event didn’t seem to affect the oldest or the very youngest groups, but 6-9 year-olds were more likely to recall after cuing events that happened at least a year later than those events that weren’t recalled after cuing.

In general, the earliest memories were several months later at the follow-up than they had been previously. The average age at the time of the earliest memory was 32 months, and 39.6 months on the follow-up interview. This shift in time occurred across all ages. Moreover, for the very earliest memory, the time-shift was even greater: a whole year.

In connection with the earlier study I mentioned, regarding the importance of language and encoding, it is worth noting that by and large, when the same memories were recalled, the same amount of information was recalled.

There was no difference between the genders.

The findings don’t rule out theories of the role of language. It seems clear to me that more than one thing is going on in childhood amnesia. These findings bear on another aspect: the forgetting curve.

It has been suggested that forgetting in children reflects a different function than forgetting in adults. Forgetting in adults matches a power function, reflecting the fact that forgetting slows over time (as is often quoted, most forgetting occurs in the first 24 hours; the longer you remember something, the more likely you are to remember it forever). However, there is some evidence that forgetting in children is best modeled in an exponential function, reflecting the continued vulnerability of memories. It seems they are not being consolidated in the way adults’ memories are. This may be because children don’t yet have the cognitive structures in place that allow them to embed new memories in a dense network.

Children’s ability to remember past events improves as they get older. This has been thought by many to be due to the slow development of the prefrontal cortex. But now brain scans from 60 children (8-year-olds, 10- to 11-year-olds, and 14-year-olds) and 20 young adults have revealed marked developmental differences in the activity of the mediotemporal lobe.

The study involved the participants looking at a series of pictures (while in the scanner), and answering a different question about the image, depending on whether it was drawn in red or green ink. Later they were shown the pictures again, in black ink and mixed with new ones. They were asked whether they had seen them before and whether they had been red or green.

While the adolescents and adults selectively engaged regions of the hippocampus and posterior parahippocampal gyrus to recall event details, the younger children did not, with the 8-year-olds indiscriminately using these regions for both detail recollection and item recognition, and the 10- to 11-year-olds showing inconsistent activation. It seems that the hippocampus and posterior parahippocampal gyrus become increasingly specialized for remembering events, and these changes may partly account for long-term memory improvements during childhood.

Last year I reported on a study involving 210 subjects aged 7 to 31 that found that in contrast to the adult brain, most of the tightest connections in a child's brain are between brain regions that are physically close to each other. As the child grows to adulthood, the brain switches from an organization based on local networks based on physical proximity to long-distance networks based on functionality. Now the same researchers, using five-minute scans from 238 people aged 7 to 30, have looked at nearly 13,000 functional (rather than structural) connections and identified 200 key ones. On the basis of these 200 connections, the brains could be identified as belonging to a child (7-11) or an adult (25-30) with 92% accuracy, and adolescents or adults with 75% accuracy. Moreover, the most important factor in predicting development (accounting for about 68%) was the trimming of the vast number of childhood connections.

Apart from emphasizing the importance of pruning connections in brain development, the main value of this research is in establishing an effective analytic method and baseline measurements for normal development. It is hoped that this will eventually help researchers work out indicators for various developmental disorders.

Findings that children are less likely than adults to distort memories when negative emotions are evoked has significant implications for the criminal justice system. Experiments involving children aged seven and 11, and young adults (18-23) found that when they were shown lists of closely related emotional words (e.g. pain, cut, ouch, cry, injury), they would tend to mistakenly remember a related word (e.g. hurt) although it had not been present. Despite the prevailing theory that being involved in a very negative experience focuses your mind and helps you notice and remember details, words that had negative emotional content produced the highest levels of false memory. With arousal (such as would be evoked in a traumatic experience), memory was distorted more. These tendencies increased with age.

A study of 80 pairs of middle-income Canadian mothers and their year-old babies has revealed that children of mothers who answered their children's requests for help quickly and accurately; talked about their children's preferences, thoughts, and memories during play; and encouraged successful strategies to help solve difficult problems, performed better at a year and a half and 2 years on tasks that call for executive skills, compared to children whose mothers didn't use these techniques.

Although we initially tend to pay attention to obvious features such as hair, it has been long established that familiar faces are recognized better from their inner (eyes, nose, mouth) rather than their outer (hair, hairline, jaw, ears) parts1. Studies have shown that this advantage of inner features does not occur in children until they’re around 10—11 years old. Children younger than this tend to use outer features to recognize people they know2.

Studies investigating the inner-face advantage have used photographs in which parts of faces have been cropped. This may be confusing to young children. It was thought that inner-face processing would be facilitated if blurring was used instead. Accordingly, in this study photographs in which either the inner face or the outer features are blurred were used.

Although it was thought that this would encourage inner-face processing, children seemed to find it harder. Extending the experiment to adolescents, it was found that the inner-face advantage typical of adults, did not appear until 14—15 years of age. A further experiment with learning-disabled adolescents, with a mental age of 5—8 years, found no shift to inner-face processing. This suggests that the shift to inner-face processing is a developmental change, rather than simply reflecting a need to gain sufficient experience in face-processing.

References

1. Ellis, H.D., Shepherd, J.W. & Davies, G.M. 1979. Identification of familiar and unfamiliar faces from internal and external features: Some implications for theories of face recognition. Perception, 8, 431-439.

2. Campbell, R. & Tuck, M. 1995. Children’s recognition of inner and outer face-features of famous faces. Perception, 24, 451-456.

Campbell, R., Walker, J. & Baron-Cohen, S. 1995. The use of internal and external face features in the development of familiar face identification. Journal of Experimental Child Psychology, 59, 196-210.

Campbell, Ruth, Coleman, Michael, Walker, Jane, Benson, Philip J., Wallace, Simon, Michelotti, Joanne & Baron-Cohen, Simon. 1999. When does the inner-face advantage in familiar face recognition arise and why? Visual Cognition, 6(2), 197-216.

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

Math theory explains children's cognitive development

Around age five, children begin to understand that if John is taller than Mary, and Mary is taller than Sue, then John is also taller than Sue – Transitive Inference. They also begin to understand that there are more fruit than apples in a grocery store – Class Inclusion. Now a mathematical theory explains why these two reasoning skills appear at the same time. It seems that both involve the ability to apply two lines of thinking about a problem at the same time, whereas younger children are limited to one. The theory provides a good account not only of Transitive Inference and Class Inclusion, but also five other forms of inference that are acquired around the same age: Matrix Completion, Cardinality, Card Sorting, Balance Scale, and Theory of Mind.

Phillips, S., Wilson, W. H., & Halford, G. S. (2009). What Do Transitive Inference and Class Inclusion Have in Common? Categorical (Co)Products and Cognitive Development. PLoS Comput Biol, 5(12), e1000599. doi: 10.1371/journal.pcbi.1000599. Full text available at http://dx.plos.org/10.1371/journal.pcbi.1000599

http://www.eurekalert.org/pub_releases/2009-12/plos-omr120709.php

Genes more important for IQ as children get older

Data from six studies carried out in the US, the UK, Australia and the Netherlands, involving a total of 11,000 pairs of twins, has revealed that genes become more important for intelligence as we get older. The researchers calculated that genes accounted for some 41% of the variation in intelligence in 9 year olds, rising to 55% in 12 year olds, and 66% in 17 year olds. It was suggested that as they get older, children get better at controlling (or perhaps are allowed to have more control over) their environment, which they do in a way that accentuates their ‘natural’ abilities — bright children feed their abilities; less bright children choose activities and friends that are less challenging.

Haworth, C.M.A. et al. 2009. R Plomin The heritability of general cognitive ability increases linearly from childhood to young adulthood. Molecular Psychiatry, advance online publication 2 June 2009; doi: 10.1038/mp.2009.55

http://www.newscientist.com/article/mg20327174.600-genes-drive-iq-more-as-kids-get-older.html

Brain's organization switches as children become adults

Imaging studies of the brain while it is supposedly doing nothing have identified four brain networks with varying responsibilities. The networks typically involve tight links between several brain regions that are physically distant from each other. A new study involving 210 subjects aged 7 to 31 has now found that in contrast to the adult brain, most of the tightest connections in a child's brain are between brain regions that are physically close to each other. As the child grows to adulthood, the brain switches from an organization based on local networks based on physical proximity to long-distance networks based on functionality.

Fair, D.A. et al. 2009. Functional Brain Networks Develop from a “Local to Distributed” Organization. PLoS Computational Biology, 5(5), e1000381. Full text available at http://www.ploscompbiol.org/article/info%3Adoi%2F10.1371%2Fjournal.pcbi.1000381

http://www.physorg.com/news161605421.html
http://www.physorg.com/news160920910.html
http://www.livescience.com/health/090518-child-brain.html

Maturity brings richer memories

New research suggests adults can remember more contextual details than children, and that this is related to the development of the prefrontal cortex. While in a MRI scanner, 49 volunteers aged eight to 24 were shown pictures of 250 common scenes and told they would be tested on their memory of these scenes. In both children and adults, correct recognition of a scene was associated with higher activation in several areas of the prefrontal cortex and the medial temporal lobe when they were studying the pictures. However, the older the volunteers, the more frequently their correct answers were enriched with contextual detail. These more detailed memories correlated with more intense activation in a specific region of the PFC. A number of studies have suggested that the PFC develops later than other brain regions.

The report appeared in the August 5 advance online edition of Nature Neuroscience.

http://www.physorg.com/news105549812.html
http://www.eurekalert.org/pub_releases/2007-08/miot-msm080107.php

A first glimpse at healthy brain and behavioral development

Initial data from the National Institutes of Health (NIH) MRI Study of Normal Brain Development, a large, population-based study that began in 1999 and is documenting structural brain development and behavior from birth to young adulthood, has revealed that:

  • Norms were higher with only healthy children being considered (the study excluded children who had any signs or known risk of serious neurological or psychiatric disorders).
  • Gender differences were less evident. Boys performed better on perceptual analysis, and girls performed better on processing speed and motor dexterity. The slight advantage girls showed in verbal learning disappeared by adolescence. There was no difference in math ability.
  • Income predicted IQ and academic achievement, but lower-income children performed better than in previous studies, with the study being restricted to healthy children.
  • Performance climbed steeply from age 6, but leveled off overall for most tests between 10 and 12 years of age, then improved more slowly or not at all during adolescence.

For more information see http://www.brain-child.org/.

Waber, D.P. et al. 2007. The NIH MRI Study of Normal Brain Development: Performance of a Population Based Sample of Healthy Children Aged 6 to 18 Years on a Neuropsychological Battery. Journal of the International Neuropsychological Society, 13, 1-18.

http://www.eurekalert.org/pub_releases/2007-05/chb-afg051607.php
http://www.eurekalert.org/pub_releases/2007-05/nion-nst051507.php
http://www.physorg.com/news98692796.html
http://sciam.com/article.cfm?articleID=A15FAD05-E7F2-99DF-34B5A1856E790722&chanID=sa003

Kids can remember events even if they can't remember times

How do we remember when an event has occurred? Most of the time we do it by reconstructing the event and inferring the time from details stored. Given that, it should perhaps be no surprise to learn that while children aged 4 through 13 can recall the details of an event fairly well, they are unable to extrapolate further and link those details with a specific time of year, even when it occurs around a major holiday. The finding has implications for legal testimony, where lawyers are inclined to cast doubt on memories if the child is unable to recall when the event occurred.

Friedman, W.J. & Lyon, T.D.2005. Development of Temporal-Reconstructive Abilities. Child Development, 76(6), 1202

http://www.eurekalert.org/pub_releases/2005-11/sfri-kcr110805.php

Development of working memory with age

An imaging study of 20 healthy 8- to 30-year-olds has shed new light on the development of working memory. The study found that pre-adolescent children relied most heavily on the prefrontal and parietal regions of the brain during the working memory task; adolescents used those regions plus the anterior cingulate; and in adults, a third area of the brain, the medial temporal lobe, was brought in to support the functions of the other areas. Adults performed best. The results support the view that a person's ability to have voluntary control over behavior improves with age because with development, additional brain processes are used.

http://www.eurekalert.org/pub_releases/2004-10/uopm-dow102104.php

Reese, E. & Brown N. 2000. Reminiscing and recounting in the preschool years. Applied Cognitive Psychology, 14, 1-17.

Finding: Parents can help their child remember events that have happened to them by reminiscing with them (recalling with them events that they have shared) and encouraging them to recall details about unshared events.

Talk about past events can be classified as either reminiscing (discussingshared experiences) or recounting (discussing unshared experiences).
This study looked at reminiscing and recounting between preschoolers and their mothers. Forty children between three and five participated in the experiment. It was found that children reported more unique memory information when they were discussing unshared experiences (recounting) rather than shared. Mothers who provided morememory information during reminiscing and asked for more information during recounting had children who reported more unique information about events.

Buckner, J.P. & Fivush, R. 1998. Gender and self in children's autobiographical narratives. Applied Cognitive Psychology, 12, 407-29.

Finding: Gender differences in conversational style seem to appear at an early age. At age 8, girls' recounting of personal experiences are already more detailed and socially contexted than boys' narratives are.

This study looked at the differences between girls and boys in recounting personal experiences. The children were aged eight, and from a middle-class background. As has tended to be found with adults, it was found that the girls' narratives were longer, more coherent and more detailed than were the boys' narratives. The girls' narratives also tended to mention more people and more emotions, and to be placed in a social context.