Experiments have proved lack of sleep as a cause of death. Lab mice that are deprived of sleep for three to four consecutive days eventually die. Lack of sleep for a long period of time, especially when combined with excessive fatigue, poses a serious threat to our health.

There are intensive research efforts to understand the mysterious workings of the biological mechanisms underlying sleep. Human beings spend almost a third of their lives in sleep. Yet, the basic sleep mechanism and its functions are still not completely known. Each of many theories proposed for understanding the secrets of sleep provide different evidence, but no guaranteed results have been attained so far. Initially, sleep was considered a rest period. However, although brain activity lowers during sleep, the brain continues actively working. It can be said that the brain rests itself by working during sleep.

Scientists classify a person’s state of consciousness as one of three stages:

1. Wakefulness
2. REM sleep
3. Deep sleep

According to this classification, sleep is divided into deep sleep and REM (Rapid Eye Movement) sleep. During a night’s sleep, there is a loop of REM sleep and deep sleep. Approximately 90 minutes of deep sleep is followed by REM sleep, which lasts between 5 and 30 minutes. Approximately 75% of the total sleep span is deep sleep; 25% is REM sleep. REM sleep happens while slipping into sleep from wakefulness. Just before waking from sleep, a short-term REM is observed.

During the first hours of sleep, REM spans are shorter, and they grow longer during the last hours of sleep. If a person is extremely tired, they experience extremely short REM sleep spans within the first hour of their sleep. They may even slip into deep sleep without REM. Right after mid-sleep, REM sleep periods last longer. If a person is deprived of all or partial sleep – such as the deep sleep or REM – they will need to sleep longer at the next opportunity. If they are deprived of REM sleep or deep sleep for longer periods, they will have longer deep sleep.

REM Sleep

REM (Rapid Eye Movement) is given this name due to the intensive and fast eye movements during this sleep stage. During REM, not only the eyes but also hands, arms, legs, and fingers move. An onlooker may think the sleeper is fully awake. However, scientists are unable to fully explain the reason why it is difficult waking a person in REM, although they are active as if they are awake – this is a paradox. In fact, a person in deep sleep may be awakened easier, by either sound or touch. If it is difficult to wake a person during the REM stages in their sleep, it may also be considered as a paradox for that person to wake from REM sleep.

During REM sleep, contrary to rapid eye movements and gestures, a person’s muscles are extremely relaxed and soft, to the extent of a wrist drop. This is called REM paralysis.

The reasons, mechanisms, and even benefits of REM sleep are not known for certain. The newest theory in sleep research claims the relationship between REM sleep and acetylcholine secretion. Acetylcholine is a brain hormone that triggers movement. Yet, acetylcholine typically causes wakefulness. This, too, appears as another paradox.

Dreams seen during the REM stage are remembered more clearly. The limbic system, including the hippocampus and amygdala, is active during REM sleep, thus it is assumed that it is easier to commit dreams to memory during this stage. The hippocampus is tasked with committing (reinforcing) information.

During REM sleep, a person’s heartbeat and breathing are more frequent and irregular. This also relates to what a person sees in their dream. During this stage, the basal metabolism rate is higher or equal to that of wakefulness. Electroencephalography (EEG) readings register beta waves, which normally show during wakefulness. Alpha waves show during times of calm, when the brain rests during wakefulness, such as at times when one closes their eyes and dispels thoughts. However, when the brain is actively dealing with an issue or when a person experiences an upset, beta waves appear. Beta waves also show during REM stage. This shows that the brain is active during REM stage.

Deep sleep

This stage of sleep is also called low wave sleep or delta sleep. During this stage, movements are at minimum, and the muscle tone is harder. Heartbeat, breathing, basic metabolic rate, and blood pressure are low. Internal organs like the stomach, intestines, urinary tract, and even the liver minimize their activities and slip into an actual rest.

During this stage, dreams and even nightmares may also be seen. However, one cannot remember a majority of dreams when they wake up. It is assumed that the traffic between the cortex and the lower structures of the brain are disengaged during the deep sleep stage. People wake up from nightmares, only to usually remember the last part.

EEG readings during deep sleep stage show delta waves. The presence of delta waves hints at the disengaged traffic between the cortex and the lower nervous system components (thalamus, hypothalamus, brain stem, hippocampus). This condition also shows that the person is in deep rest, free from pain and other bodily stimuli.

Secreted at night, melatonin is a hormone that protects against cancer and slows down the aging process. Melatonin also plays a role in lowering bad cholesterol (LDL) and balancing body heat and blood pressure. Melatonin secretion starts around 10:00 p.m. and reaches its maximum around 5:00 a.m. That’s why, the most ideal sleep is after 10:00 p.m. when melatonin secretion starts. Bedside lamps are not suggested as they hinder the secretion of this night-bound hormone. People should also avoid conditions such as stress, smoking, extreme lighting, lack of adequate daylight, and working at lengthy periods, which lower melatonin level.

First, we should emphasize that Prof. Zewail’s statements resonate very well with what famous scholar Ibn-al Haytham said 10 centuries ago:

“The seeker after truth is not one who studies the writings of the ancients and, following his natural disposition, puts his trust in them, but rather the one who suspects his faith in them and questions what he gathers from them, the one who submits to argument and demonstration, and not the sayings of a human being whose nature is fraught with all kinds of imperfection and deficiency. Thus the job of the man who investigates the writings of scientists, if learning the truth is his goal, is to make himself an enemy of all that he reads, and applying his mind to the core and margins of its content, attack it from every side. He should also suspect himself as he performs his critical examination of it, so that he may avoid falling into either prejudice or leniency.”

Every human being is given the ability to think. That is what makes all the progress of humanity possible. When we think we process the information we receive based on what we already know and we usually make judgments. Nobody can deny that all humans go through this process many times every day. But we can question the outcome of our thinking process, that is, our judgments. Many times, we can be wrong in our judgments, and this is where “critical” thinking might help.

Today, most people learn how to think systematically at schools, particularly during university education. In fact, according to Derek Bok, the former president of Harvard University, faculty members in the US almost unanimously agree that “teaching critical thinking” is the principal aim for undergraduate education. Although many have great conviction that critical thinking is very important, there is no universal definition for it. The American Philosophical Association gives the following definition:

“Purposeful, self-regulatory judgment which results in interpretation, analysis, evaluation and inference as well as explanation of the evidential, conceptual and methodological considerations on which a judgment is based.”

Based on this definition and what we quoted from Ibn-al Haytham, we can identify the following points about critical thinking:

1) When you read or hear a statement, do not accept it without question.

2) Try to find other information that can support or disprove the statement, try to come up with ways to demonstrate validity or falsehood of the statement, and test the statement.

3) As you perform your critical examination, be aware of your own deficiencies as a human. Consider your own biases, numerous possibilities of making mistakes in your judgments, or prejudices you can assume without knowing.

4) Be aware of the method you use for evaluating a claim, and think about both its strengths and weaknesses.

Critical thinking, if we develop the habit of performing it, can help us every day. Consider how you receive information in the twenty-first century. Typically, you read a newspaper or watch news on TV. If you just accept what you hear and see, then you can sometimes be manipulated or fooled. In an ideal world we can assume that objective presentation of news is possible. In the real world, however, those who transfer news bits to the population are also humans who are prone to similar biases. Many times a newspaper or a TV station represents certain values, ideologies, or supports some political positions. Besides, news reporting is so much commercialized that news editors and reporters also think about how to attract readers, and might use catchy words deliberately. Therefore, everyone should ask questions, clarify certain interpretations, and need to fight their own biases before reaching conclusions whenever they encounter a media report. An increased number of critical thinkers will help create a healthy debate about controversial issues.

We can expand this critical approach with respect to news media to our formal education experiences. At schools, our teachers deliver new information every day. We also read our textbooks. Typical student tendency might be to just accept what they hear and what they read, though this may depend on the student’s intellectual development and the culture of the society. If we perform critical thinking in the classroom and while reading textbooks, we can grow intellectually much more than otherwise. We can retain what we learn more easily. In addition, the purpose of schools and universities is to prepare us for life. We all know that in real life problems are never well defined, and most of the time you cannot readily find an authoritative figure or a manual to consult. Therefore, it is imperative that we teach students to question what they hear and what they read. In order to encourage students to perform more critical thinking in the classroom, however, we might need to find alternative modes of teaching and move away from conventional method of active teacher – passive students.

Although we must strive to teach critical thinking, we should also recognize the fact that there are roughly three distinct phases in our lives with respect to thinking, and not everyone is in the same phase at a given time. When we are young we usually think that every question has a certain answer, and it is just a matter of finding the authority who can give that answer. As we grow up, however, we realize that sometimes many authoritative figures may disagree. This observation may make one a relativist; that is, we might start thinking that depending on who you ask the answer varies, and it is all relative. As we further grow in our intellectual development, we usually notice that although people disagree on certain topics, we should always make some decisions, and some points of view have more support than others. By performing critical thinking we can filter out less reliable information, and come to better conclusions. In some complex cases, however, we might realize that there is no single correct judgment, and circumstances might lead us down different paths.

In the context of these three different phases, we can safely claim that on the average you expect the ability to think critically improve, as we get older. Elementary school children are most likely to think that there is a correct answer to every question. In middle and high school, many students will realize that there may be different answers to the same question depending on whom you ask. By the time of their graduation we expect university students to learn how to critically evaluate information. This final outcome, though very significant for a healthy society, highly depends on our teaching strategies. That is, if rote memorization is more valued than critical evaluation, then university graduates might stay as naive relativists or even worse.

Critical thinking is extremely crucial to separate the truth from myth. A well known example is about our brains. In many societies, it is said that people typically use about 10% of their brain, and geniuses like Einstein are able to use more of their brains. Some questions to ask are as follows:

1) What does it mean to use 10% of the brain?

2) Who provides this information? Is s/he a neuroscientist?

3) How do people measure brain usage?

4) Einstein lived long time ago. Did they measure his brain activity the same way as the control group to conclude that he used more of his brain?

When we search for answers to these questions, we typically find that there is no basis for this claim. It does not mean much. Maybe the statement originally meant that many do not use their brain’s full potential, which might be true. But, when the statement is compared to what we know about brain science, then it becomes a myth.

While everyone and every profession benefits from critical thinking, some jobs require critical thinking more than others. Scientists, for example, have an obligation to be extremely critical of others’ work. Let us remember that Ahmad Zewail and Ibn-al Haytham are both scientists. In science, there is a process called “peer review,” which is extremely useful. Any research carried out becomes scientific knowledge after it is submitted to the critical reviews of other scientists in the field. Any contribution submitted to a scientific journal is tested for correctness and originality. At the end of the critical review, the reviewers submit a report to the editors of the journal, who then make a decision. Many times the authors of the article are asked questions or are asked to make modifications, to which they may respond. In short, we can safely state that a scientist must be a critical thinker, or otherwise s/he cannot perform his or her research duties, and s/he is prone to become a repeater of someone else’s ideas, and may go awry at times.

From what we explained so far, it is probably obvious that we need some background knowledge about a subject in order to become a real critical thinker. It is clear that if someone knows nothing about urban planning, for example, it is very hard for him to critically examine any work on urban planning. This straightforward observation suggests that most people cannot be critical thinkers even if they want to be. Fortunately, this conclusion is only partially true because critical thinking is not a single discrete outcome but rather a continuum. Although knowledge of a topic makes us better thinkers in a field, there are always some minimal questions one can ask. For example, there is a controversial topic and someone makes some crucial statements about it. Even if you don’t know about the topic, you can ask whether the speaker is an expert on the topic or not. Or you can ask about what kind of evidence he is using. Does the evidence presented come from a reliable source? Why may this person take this side of the argument, but not other alternatives? Are there any other alternative approaches to the same issue? That is, at minimum, the answers to these questions can help us develop sound judgment.

A great case in which many feel lost is the global warming debate. By doing a simple web search on global warming you can find articles both supporting and denying human-caused global warming. But which point of view should you believe? Although there is consensus that global warming is happening, there is disagreement about whether it is caused by our technological conveniences, or whether it is just a result of natural temperature fluctuations in geological time scales (hundreds of thousands of years).

Indeed, the question “which point of view should you believe?” may not be the correct question. Instead, perhaps we should ask why people feverishly debate about this issue. Why do people care a lot about various aspects of global warming and atmospheric science research? A little investigation shows that there is a lot at stake. Accepting that excessive use of energy by humans, which leads to increase in carbon dioxide levels in the atmosphere, causes global warming has many economic, political, and social consequences. If you agree that man-made global warming can trigger many other events which can eventually make the climate on the Earth fall off-balance, then it follows that many people in the world must change their lifestyles, and this may also mean that some big companies must make changes which may hurt their profits, or that some governments might not use certain political leverage in international relations.

Obviously, it will not be easy to accept such findings, even if they come from some prominent scientists. There are, in fact, scientists on both sides of the aisle. This is because atmospheric science is extremely complex, and even with our best computers modeling the changes in the atmosphere it remains a very hard task. Further investigation also shows that there are different types of evidence people use. Some point to reports prepared with sponsorship from some governments or companies. Some expand on disagreements among scientists, and conclude that no action is needed until all the claims are proven. As we mention above, there are also scientific articles published in “peer-reviewed” journals. The Intergovernmental Panel on Climate Change (IPCC) puts out consensus statements. In short, it is a complex issue, and the credibility of evidence varies. We leave further investigation on climate change to practice critical thinking to the interested reader.

Critical thinking requires effort, sometimes a lot of effort. Lazy personalities and those who do not like to engage their mental abilities are less likely to perform critical thinking. In this regard, critical thinking is also very different from rote criticism. Rote criticism does not require much effort; typically the statements of the person performing the critique do not have a sound basis. While critical thinking is necessary for a healthy society to clarify especially certain controversial topics, mere criticism of one another can be a means to create unnecessary enmity among individuals.

Critical thinking does not mean that we need to become a skeptic and reject everything. In fact, descriptions of critical thinking involve paying special attention to certain criteria and standards. In practice, if one does not have any reference it becomes very hard to move forward in thought. What needs to be emphasized is that the world is not black and white. It displays a vast variety of colors. We can give more weight to certain colors than to others. What we cannot claim is that there is a single color, and all others are false. We can certainly have certain beliefs, paradigms, and values. These may become the basis for some of the criteria and standards against which we evaluate new information. At times, great events and findings might force us to evaluate certain paradigms we take for granted, too. However, such sharp turns do not happen frequently in the life of an individual or society.

In conclusion, critical thinking skills are essential for everybody. We should be aware of our own shortcomings, biases, prejudgments, as well as the sources, agendas, worldviews, paradigms and the information channels we use when we process new information. Critical thinking cannot be done instantly; it requires effort and courage to come face-to-face with one’s own errors. Teaching critical thinking is not instant, either. Formal and informal education institutions must strive to develop critical thinking skills in students, and such an endeavor might require modification of our approach to teaching. In the final evaluation, it is extremely crucial that we take the necessary steps to increase the number of critical thinkers in the world for the benefit of all humankind.

Dr. Ertan Salik is an Assistant Prof. of Physics at California State Polytechnic Univ, Pomona. As well as teaching and conducting physics research Dr. Salik is currently involved in many education programs.

Notes

1. The Fountain magazine, interview with Ahmad Zewail by Nuh Gedik, Jan-Feb 2009, issue 67.
2. Steffens, Bradley. Ibn-al Haytham: First Scientist, Morgan Reynolds Publishing. Also see Book Review in The Fountain Magazine, issue 63, May-June 2008.
3. Bok, Derek. Our Underachieving Colleges, Princeton Univ Press, 2006.
4. Critical Thinking: A Statement of Expert Consensus for Purposes of Educational Assessment and Instruction, American Philosophical Association Report, 1990.
5. IPCC consensus statements can be downloaded from http://www.ipcc.ch/.