attention problems

Prenatal exposure to pesticides linked to attention problems

September, 2010

In a study of young Mexican-American children, higher prenatal exposure to pesticides was significantly associated with ADHD symptoms at age 5.

A study following over 300 Mexican-American children living in an agricultural community has found that their prenatal exposure to organophosphate pesticides (measured by metabolites in the mother’s urine during pregnancy) was significantly associated with attention problems at age 5. This association was stronger among boys, and stronger with age (at 3 ½ the association, although present, did not reach statistical significance — perhaps because attention disorders are much harder to recognize in toddlers). Based on maternal report, performance on attention tests, and a psychometrician’s report, 8.5% of 5-year-olds were classified as having ADHD symptoms. Each tenfold increase in prenatal pesticide metabolites was linked to having five times the odds of scoring high on the computerized tests at age 5. The child’s own level of phosphate metabolites was not linked with attention problems.

Organophosphate pesticides disrupt acetylcholine, which is important for attention and short-term memory. While the exposure of these children to pesticides is presumably higher and more chronic than that of the general U.S. population, food is a significant source of pesticide exposure among the general population.

Reference: 

Marks AR, Harley K, Bradman A, Kogut K, Barr DB, Johnson C, et al. 2010. Organophosphate Pesticide Exposure and Attention in Young Mexican-American Children. Environ Health Perspect :-. doi:10.1289/ehp.1002056
Full text available at http://ehp03.niehs.nih.gov/article/fetchArticle.action?articleURI=info%3...

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Negative stereotypes affect learning, not just performance

August, 2010

Following on from several studies showing that being reminded of a negative stereotype for your group (be it race or gender) affects your test performance, a new study shows it also impairs learning.

A number of studies have demonstrated that negative stereotypes (such as “women are bad at math”) can impair performance in tests. Now a new study shows that this effect extends to learning. The study involved learning to recognize target Chinese characters among sets of two or four. Women who were reminded of the negative stereotypes involving women's math and visual processing ability failed to improve at this search task, while women who were not reminded of the stereotype got faster with practice. When participants were later asked to choose which of two colored squares, imprinted with irrelevant Chinese characters, was more saturated, those in the control group were slower to respond when one of the characters had been a target. However, those trained under stereotype threat showed no such effect, indicating that they had not learned to automatically attend to a target. It’s suggested that the women in the stereotype threat group tried too hard to overcome the negative stereotype, expending more effort but in an unproductive manner.

There are two problems here, it seems. The first is that people under stereotype threat have more invested in disproving the stereotype, and their efforts may be counterproductive. The second, that they are distracted by the stereotype (which uses up some of their precious working memory).

Reference: 

[1686] Rydell, R. J., Shiffrin R. M., Boucher K. L., Van Loo K., & Rydell M. T.
(2010).  Stereotype threat prevents perceptual learning.
Proceedings of the National Academy of Sciences.

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Background music can impair performance

August, 2010

Music may help you get in the mood for learning or intellectual work, but background music is likely to diminish your performance.

While studies have demonstrated that listening to music before doing a task can improve performance on that task, chiefly through its effect on mood, there has been little research into the effects of background music while doing the task. A new study had participants recall a list of 8 consonants in a specific order in the presence of five sound environments: quiet, liked music, disliked music, changing-state (a sequence of random digits such as "4, 7, 1, 6") and steady-state ("3, 3, 3"). The most accurate recall occurred when participants performed the task in the quieter, steady-state environments. The level of recall was similar for the changing-state and music backgrounds.

Mind you, this task (recall of random items in order) is probably particularly sensitive to the distracting effects of this sort of acoustical variation in the environment. Different tasks are likely to be differentially affected by background music, and I’d also suggest that the familiarity of the music, and possibly its predictability, also influence its impact. Personally, I am very aware of the effect of music on my concentration, and vary the music, or don’t play at all, depending on what I’m doing and my state of mind. I hope we’ll see more research into these variables.

Reference: 

[1683] Perham, N., & Vizard J.
(2010).  Can preference for background music mediate the irrelevant sound effect?.
Applied Cognitive Psychology. 9999(9999), n/a - n/a.

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Depression not necessarily associated with lack of concentration

February, 2010

A review of 35 studies has found that depression does not always lead to cognitive impairment, and that processing speed is the cognitive function most consistently affected by depression.

A review of 35 studies published between 1991 and 2007 has found that depression does not always lead to cognitive impairment. Part of the variability in findings may be due to inconsistent measurement and diagnosis of depression. Processing speed was found to be the cognitive function most consistently affected by depression. Processing speed deficits can be helped by decreasing the amount of information to process at one time.

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Video games threaten kids' attention span

July, 2010

A large study of elementary school children and college students has found greater screen time (TV and video games) is associated with more attention problems.

A study following 1,323 children in Grades 3 to 5 and 210 college students has found that children who exceeded two hours per day of screen time (TV and video games) were 1.5 to two times more likely to be considered above average in attention problems by their teachers compared to children who met the guideline. A similar association between screen media time and attention problems (self-reported) was found for the college students. A study earlier this year found U.S. children aged eight to 18 devote an average of seven hours and 38 minutes per day to entertainment media (http://www.kff.org/entmedia/entmedia012010nr.cfm ).

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Traffic noise disturbs sleep, affects morning performance

July, 2010

A sleep lab study has revealed that traffic noise during sleep produces significantly slower reaction times on a vigilance task in the morning.

It’s not just a matter of quantity; quality of sleep matters too. A study involving 72 adults (average age 40), whose sleep was monitored for 11 consecutive nights, has revealed that reaction times on a morning psychomotor vigilance task was significantly slower after exposure to recorded traffic noise during sleep. The slowing was directly related to the frequency and sound-pressure level of the nightly noise. Traffic noise has been identified as one cause of "environmental sleep disorder," which involves an environmental disturbance that causes a complaint of insomnia or daytime sleepiness. Other common causes include bright light and temperature extremes. The researchers also note that nighttime traffic noise may have even stronger effects on the performance of people who are more susceptible to sleep disturbances. Risk groups include children, shift workers, the elderly and people with chronic medical conditions. White noise, produced by fans, sound machines, and special applications for computers and smart phones, can be used to mask other noise.

Reference: 

Elmenhorst, E. et al. 2010. Nocturnal traffic noise and morning cognitive performance. Presented at SLEEP 2010, the 24th annual meeting of the Associated Professional Sleep Societies LLC, in San Antonio, Texas.

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Children living in areas where homicides committed have lower reading, verbal test scores

July, 2010

A Chicago study has found substantially lower reading scores in African-American children who were assessed directly after a local homicide. Hispanic children were not affected.

A study using data on reported homicides in Chicago 1994-2002 and two independent surveys of children and families in Chicago, has revealed that African-American children who were assessed directly after a local homicide occurred scored substantially lower on vocabulary and reading assessments than their peers from the same neighborhood who were assessed at different times. The impact of the homicide faded both with time and distance from the child's home. However, in both datasets, while the results were extremely strong for African Americans, there was no effect of local homicides for Hispanics. Because of the prevalence of homicide in the most violent neighborhoods in cities like Chicago, these results mean that some children spend about one week out of every month functioning at a low level. Whites and other ethnic groups were excluded from the study because they were almost never exposed to local homicides in the samples used.

Reference: 

[1631] Sharkey, P.
(2010).  The acute effect of local homicides on children's cognitive performance.
Proceedings of the National Academy of Sciences. 107(26), 11733 - 11738.

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Coffee consumption unrelated to alertness

July, 2010

A recent study indicates that the alertness benefits of caffeine may simply reflect the reversal of the fatiguing effects of caffeine withdrawal.

A study involving 379 individuals who abstained from caffeine for 16 hours has revealed little variance in levels of alertness after receiving caffeine. Those who were medium/high caffeine consumers reported a decrease in alertness and an increase in headache if given the placebo, neither of which were reported by those who received caffeine. However, their post-caffeine levels of alertness were no higher than the non/low consumers who received a placebo, suggesting caffeine only brings coffee drinkers back up to 'normal'. In other words, the stimulatory effects of caffeine appears to be an illusion generated by the reversal of the fatiguing effects of acute caffeine withdrawal.

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Sleep loss and temporal memory

Journal Article: 

Harrison, Yvonne & Horne, James A. 2000. Sleep loss and temporal memory. The Quarterly Journal of Experimental Psychology, 53A (1), 271-279.

Recognition memory for faces was unaffected by being deprived of sleep for 35 hours.

However, sleep-deprived subjects were significantly worse in remembering in which of two sets of photos particular faces had appeared in.

Sleep-deprived subjects who had been given significant doses of caffeine remembered the set better than those who had not, but were still poorer at remembering than those not deprived of sleep.

Although their performance was poorer, sleep-deprivation seemed to increase the subjects' belief in their own accuracy.

It seems likely that sleep-deprivation affects memory for context.

In this study, subjects were shown two sets of 12 color photographs of people’s faces (24 in total). Five minutes after seeing the last one, the subjects were then shown another 48 faces (one by one, as before) and had to say whether or not they had seen the face earlier. If so, they were asked whether they saw it in the first or second set of photographs. Half the subjects had been deprived of sleep for the previous 35 hours. Some of these had been given significant amounts of caffeine to offset their sleepiness.

It was found that the sleep-deprived subjects, whether or not they had had caffeine, were as good as the non-sleep-deprived subjects at recognizing which faces they had seen before. However, the sleep-deprived subjects were significantly worse at remembering which set the faces had appeared in. This occurred even though otherwise optimum conditions for recall existed (the test was novel, stimulating, and relatively short; it was given at the best time of day for maximum alertness).

Caffeine significantly reduced the feelings of sleepiness and did appear to improve the ability of the sleep-deprived subjects to remember which set the face had appeared in, but the level of recall was still significantly below the level of the non-sleep-deprived subjects. Caffeine made no difference to the memory performance of subjects who were not sleep-deprived.

Interestingly, sleep deprivation increased the subjects’ belief that they were right, especially when they were wrong. In this case, whether or not they had had caffeine made no difference.

It may be that the problem with temporal memory reflects a more general problem with remembering context information.

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