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Mental Performance and Circadian Rhythm

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Certainly all adults, especially parents and teachers, want children to study hard at school, get perfect scores on tests, and make good grades. Intellectual work that requires concentrating on class content and taking exams hinges on mental performance. Mental performance, however, is not just an issue in children's education?it also affects various types of tasks carried out by adults. It is clear that mental performance is a factor in the occurrence of many accidents and errors today.

An international conference held by the International Mind, Brain, and Education Society (IMBES) in Erice, Italy in May 2007 addressed the significance of mental performance in education. The society's journal, "Mind, Brain, and Education" (MBE) Vol. 2, No. 1 was a special issue devoted to this topic, and here we take up one of the articles entitled Rhythms of Mental Performance" written by Pablo Valdez, University of Nuevo Leon, and Thomas Reilly and Jim Waterhouse, Liverpool John Moores University.

Needless to say, a number of factors impinge on mental performance. First, there are external factors such as the ambient conditions of the person carrying out the task, the effects of practice, nature of the particular task, etc. To this, we can add such internal factors as the person's chronotype (morning- or night-type), time elapsed since rising, meals, naps, and lack of sleep, etc.

Analysis of mental performance in terms of cognitive science indicates that it is supported by three processes: attention, working memory, and executive function. Consequently, at the outset, the ability to sustain attention, the most basic process, is affected by lack of sleep or fatigue. This, in turn, affects other cognitive processes and can negatively affect the results of task performance in the end.

A decrease in sleeping time produces a steep decline in accuracy, which is overwhelmingly more evident in complicated tasks that require all-night work as opposed to simple tasks. Fatigue also has a strongly negative effect on the emotions and leads to a decline in motivation and decreased accuracy. It was also found that napping for at least one hour improves performance that has been diminished by no sleep the previous night.

Recently, mental performance has been found to be greatly affected by circadian rhythms, variations in physiological rhythms based on an approximate 24-hour period. Circadian rhythms control the daily cycle of biological activity, affecting not only sleep and waking, but also corticosteroid secretion, body temperature, pulse, blood pressure, urine volume, eosinophil count, etc. Human evolution, starting with chemical, cellular, and biological evolution, took place within the rhythms of sunlight and the constant alternations of morning, afternoon, and night. Perhaps as a result, we can say that circadian rhythms became embedded in the hypothalamus as a biological clock, and not surprisingly, the mental performance is dependent on them.

Mental performance and circadian rhythms are deeply interconnected in a number of ways. For example, afternoon types perform well during the day, but show poor mental performance in the early morning or late afternoon. In general, mental performance declines after noon, but more complicated tasks show greater deterioration than simpler tasks, which may be due to fatigue.

There is also an interesting parallel between mental performance and core temperature, which is the temperature in the deep structures of the body, generally considered to be rectal temperature. Naturally, the core temperature, similar to external body temperature as indicated by axillary temperature, follows a circadian rhythm and shows two peaks. A rise in the core temperature is correlated with a rise in biochemical activity in the brain, and this is considered to affect the outcome of a task.

Based on the outcome of various tasks, we can conclude that mental performance is influenced by three factors: sleep rhythm, time awake, and core temperature. There have also been attempts to construct self-rated mental performance models which would predict alertness, length of sleep, time to sleep, risk of falling asleep, etc., but these require further study.

In conclusion, the authors provide the following methods as ways to improve mental performance where studying takes place.

(1) Optimize conditions where study takes place. Improving mental performance requires actively promoting the motivation to study by creating a quiet and well-lit environment that is conducive to studying. The level of lighting depends on whether a video display unit or paper is used. In the case of a video display, the images should not be too brightly illuminated and the screen itself should neither be too dark or bright.

(2) Difficult tasks, for example, that involve calculation or reading comprehension, should not be conducted for a long time due to the effects of fatigue. If possible, it is advisable to alternate between study tasks.

(3) There is an optimal time of the day to carry out a particular type of task. As mental performance deteriorates with time awake, the morning or the first part of the day is the best time. Mental performance decreases as the afternoon progresses and time awake increases. As a result, physical activities and artistic pursuits are better suited to the end of the day. Furthermore, mental performance may be compromised at two other times of the day, but for different reasons. First, in the early morning, performance may deteriorate due to the combined effects of low body temperature and sleep inertia. During this time, body temperature has not yet risen above the nocturnal minimum. Second, mental performance tends to show a post-lunch dip immediately after lunch.

(4) Perparations for work also affect mental performance. For example, mental performance may decline because of a baby in the household, which can cause members to suffer from lack of sleep because they retire too late, rise too early, or have problems sleeping. In the worst case, it may be possible to compensate for lack of sleep by napping, the most effective time for which is just after lunch. When unable to sleep at all at night, mental performance naturally declines due to hypoglycemia resulting from overnight fasting. In this case, glucose intake is recommended, such as having breakfast before beginning work.

(5) Mental performance is affected by individual differences. Mental performance at school will be best depending on whether the individual has a morning or intermediate chronotype. Those with an evening chronotype will not demonstrate optimal mental performance or motivation to study during the early part of the day.

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