In the 18th century, an academic argument broke out in France concerning the humble heliotrope flower. The purple bloom of this flower closes up in the evening, then reopens in the morning, as if to welcome the sun—as the flower's Greek name implies.
The controversy concerned the role of the sun in the plant's behavior. One side claimed that without the sun, the flower would never open, that it was the sun's rays that gave the signal. The other side claimed that the sun's presence was coincidental: the flower had the capacity to open despite the sun—and on cloudy days, it did.
To settle the argument, the scientists placed the flower in a light-proof box. When they opened the box the following afternoon, they found the flower in full bloom (no doubt wondering where the sun's rays were). They repeated the experiment several times with the same result. It proved that the flower had its own internal timing mechanism.
When Do We Flower?
Like the heliotrope, we humans have our own internal timing mechanisms. They're called the circadian rhythms—biological patterns that recur about every 24 hours. We live in an environment of regularly occurring events. Night follows day, which follows night. Meal times tend to be regular and predictable, as do the times of human contact. Apparently these environmental stimuli—zeitgebers, as they are known to scientists—have either induced a biological response or are the result of natural cycles. Whatever the case, the human body has certain rhythms that are in tune with the zeitgebers of its environment.
To date, researchers have identified more than 100 circadian rhythms that recur daily (Mayo Clinic 1995). Perhaps the most familiar is the sleeping-waking pattern. Less well known is the variation in blood pressure, respiration rate, and temperature over a 24-hour cycle. On average, the human body temperature varies from just above 97 degrees Fahrenheit to nearly 99 degrees (Colquhoun 1971). The lowest temperature typically occurs at about 5 a.m.; the highest, at about 6 p.m.
This temperature variation may not seem significant, but research dating back more than 100 years reveals a parallel ebb and flow in the efficiency of our thinking and general functioning. In 1892, Dresslar designed an experiment to determine the relationship between efficiency and time of day. At two-hour intervals from 8 a.m. to 6 p.m., he had operators tap a telegraph key 300 times. This was repeated for six days. The average tapping speed was lowest at 8 a.m. It improved gradually until 4 p.m., when it began falling off slightly until 6 p.m.
That pattern of increasing efficiency through the waking hours to a peak in midafternoon or thereabouts has been repeated in numerous studies. Researchers have found that, in general, efficiency is at its lowest ebb in the early morning hours and at its highest at about 4 p.m., when it begins to decline.
My Time Isn't Your Time
Such results are based on average patterns. They must be tempered with the knowledge that individuals themselves may vary significantly from the average pattern. In 1963, Kleitman measured the body temperatures of two people repeatedly for a full year. He found that one person reached his temperature peak earlier in the day than the other. Significantly, just as his temperature peaked, he was also more efficient in the hand movement exercises that were part of the experiment.
Subsequent research has confirmed that some people reach their temperature peak before noon, some in the afternoon, and some in the evening. Hence, a picture emerges of the "morning person," "afternoon person," and "evening person."
If you think about your own preferences, you may be able to diagnose your pattern. When do you think most clearly? When do your problems seem easiest to solve? Whatever time that is, it almost certainly is your quality time of day.
Despite the research, our knowledge of our circadian rhythms and internal body clocks remains relatively rudimentary. Most of us know, however, that we have a best time and a worst time of the day because we are more alert and rested at predictable times. Harnessing this knowledge to the needs of students is a logical next step.
Quality Learning Time
In applying this research to education, we would ask students and teachers questions such as: Are you more apt to remember things at certain times of the day? Do you find it more difficult to understand concepts in the morning than in the evening? Teachers may also ask themselves if they should prepare tests at night.
Studies have shown that students understand material better and do better on tests at their preferred time of day. In a 1980 study, Biggers found that high school students who preferred to study in the morning graduated with a letter grade that averaged half a grade higher than those of other students. That same year, Folkard cautioned against the tendency to schedule more difficult subjects early in the morning: Many students are not at their best at that time, he explained, even though it seems many teachers are. (This is based on anecdotal evidence, as formal studies of teachers' preferred time of day have yet to be done.)
In 1983, Virostko conducted an interesting experiment in a Long Island grade school. She divided the 3rd, 4th, 5th, and 6th grades into two sections for their mathematics instruction and two for English. In the morning, one group was taught English, the other mathematics. This was reversed in the afternoon. After diagnosing the students' time preferences, Virostko could determine which students were matched and which were mismatched for each section of each subject.
The students were required to take state-mandated, standardized tests in math and English at the end of the year. Virostko predicted—accurately—that matched students would score significantly higher in the matched subject than in the mismatched subject. The following year, the groups were reversed. When the mandated tests were again given, the same held true. Students scored significantly higher in the subject in which they had scored lower the year before, and vice versa.
In 1977, Folkard and colleagues found that children's short- and long-term memory varied significantly with the time of day. Schoolchildren taught at about 3 p.m. retained material longer than those taught in the morning. Moreover, seven days later, those who read a story in the afternoon could recall more details than could students who had read it at 9 in the morning.
In 1985, Winget and others who worked for NASA's Biological Research Division observed that athletic teams instructed in the morning were able to remember the moves about as well as a person who had slept only three hours the night before. As a result, the biologists recommended that instruction in intricate maneuvers be scheduled for the afternoon.
A 1988 study led Perry and Dawson to the opposite conclusion about short-term memory. They found that short-term memory is stronger in the morning. They therefore recommended that people taking exams in the morning should review their notes right before the test. This represented a possible further refinement of our understanding of memory—that certain types of memory function better at certain times of the day.
Freeley reported in 1984 that teachers' inservice programs offered in the morning had a significantly greater chance of success. (By success, he meant their readiness to experiment in the classroom with the new techniques they learned.) This finding, however, was probably due to the fact that the majority of teachers in her study were morning people.
Night School, Day School
In the best of all possible worlds, each school district would have three parallel systems. The principal school for the majority of students would hold classes in the late morning through the afternoon. Two smaller schools—one open earlier in the morning and the other in the evening—would cater to the remaining students. Classes would begin just as the students began to approach their period of peak efficiency and understanding. For most students, according to the research of Dunn and Dunn (1993), that time is mid-morning—about 11 a.m. A significant number of students, however, are morning people. And there are evening people, as well.
The teachers assigned to these schools would match the students. Thus each school would be staffed by teachers who were at their intellectual best just as their students were at their most receptive. Competition for morning jobs would be intense, however, because many teachers tend to be at their best in the morning. (That generalization, supported by research conducted by Freeley [1984], among others, should not come as a surprise. Based on my own research, about 33 percent of high school students appear to have no time-of-day preferences; fewer than 10 percent prefer the morning; and fewer than 10 percent, the late morning. Fifteen percent prefer the afternoon, and another 15 percent prefer the evening. The remaining students have two time preferences—or even three.)
We'll have to conduct further research to find out the differences in achievement (if any) between students with no preferences and those who prefer one or even several times of day.
Most school systems serve morning people best, and the students who are most successful tend to be those who are able to make the most of the system.
Such a three-pronged school system is an intriguing possibility. One wonders how many students are at a serious disadvantage because school hours are totally at odds with their peak hours. Any teacher knows the challenge of teaching a class of sleepy young people at 8:30 in the morning. These same students may be alert and responsive during classes later in the day.
For some students, class scheduling is particularly critical. In 1981, Lynch found that the truancy rate in one high school dropped when the time preferences of the truants—almost entirely afternoon and evening people—were accommodated by classes later in the afternoon.
Based on my own research, no one has ever explored the link between success in school and students' peak times of the day. It would make an interesting study, particularly because fully 70 percent of students, according to Dunn and Dunn's studies (1993), are not morning people. The time of day that students attend classes and study could be both a key to success and a clue to failure.
