How Does Sleep Deprivation Affect the Brain?

How many hours of sleep does the average person require? The American Academy of Sleep Medicine and the Sleep Research Society recently convened an expert panel which reviewed over 5,000 scientific articles and determined that sleeping less than 7 hours in adults (ages 18-60) was associated with worsening health, such as increased obesity and diabetes, higher blood pressure as well as an increased risk of stroke and heart disease. In addition to increasing the risk for illnesses, inadequate sleep is also linked to impaired general functioning, as evidenced by suppressed immune function, deficits in attention and memory, and a higher rate of errors and accidents. Since at least one third of adults report that they sleep less than 7 hours a day (as assessed by the Centers for Disease Control and Prevention in a survey of 444,306 adults), one can legitimately refer to insufficient sleep as a major public health issue. Even though insufficient sleep and other sleep disorders have reached epidemic-like proportions affecting hundreds of millions of adults world-wide, they are not adequately diagnosed and treated when compared to medical risk factors and conditions. For example, in most industrialized countries, primary care physicians perform annual blood pressure and cholesterol level checks, but do not routinely monitor the sleep duration and quality of their patients.

One reason for this may be the complexity of assessing sleep. Checking the blood cholesterol level is quite straightforward and provides a reasonably objective value which is either below or above the recommended cholesterol thresholds. However, when it comes to sleep, matters become more complicated. The above-mentioned expert panel acknowledged that there can be significant differences in the sleep requirements of individuals. Those who suffer from illnesses or have incurred “sleep debt” may require up to 9 hours of sleep, and then there are also significant environmental and genetic factors which can help determine the sleep needs of an individual. The average healthy person may need at least seven hours of sleep but there probably groups of individuals who can function well with merely 6 hours while others may need 9 hours of sleep. Then there is also the issue of the sleep quality. Sleeping for seven hours between 10 pm and 5 am has a higher quality of sleep than sleeping between 6 am and 1 pm because the latter will be associated with many more spontaneous awakenings and interruptions as well as less slow-wave sleep (a form of “deep sleep” characterized by classical slow wave patterns on a brain EEG recording during sleep). Unlike the objective cholesterol blood test, a true assessment of sleep would require an extensive sleep questionnaire asking details about sleep history and perhaps even recording sleep with activity monitors or EEGs.

Another reason for why insufficient sleep is not treated like other risk factors such as cholesterol and blood pressure is that there aren’t any easy fixes for poor sleep and the science of how poor sleep leads to cognitive deficits, diabetes and heart disease is still very much a topic of investigation.

In the case of cholesterol, numerous studies have shown that cholesterol levels can be effectively lowered by taking a daily medication such as a statin and that this intervention clearly lowers the risk of heart attacks and stroke. Furthermore, the science of how cholesterol causes stroke and heart disease has been worked out quite well by identifying the molecular mechanisms of how cholesterol contributes to the build-up of plaque in the arteries which can then lead to heart attacks and stroke. When it comes to sleep, on the other hand, multi-faceted interventions are required to restore healthy sleep levels. Medications to help patients sleep can be used in certain circumstances for a limited time but they are not a long-term solution. Instead, improving sleep requires individualized solutions such as developing a sleep schedule of fixed bed-times, minimizing the use of digital screens in the bedroom, and avoiding caffeine, large meals, nicotine or alcohol just before bedtime. The complexity of assessing and treating insufficient sleep also makes it very difficult to prove the efficacy of interventions. Controlled clinical studies can demonstrate that a cholesterol-lowering medication reduces the risk of heart attacks by treating thousands of patients with the active medication when compared to thousands of patients who receive a placebo, but how do you test the efficacy of individualized sleep interventions in thousands of patients?

Understanding the precise mechanisms by which insufficient sleep impairs our functioning and health has therefore become a major topic of research with significant advances that have been made in the past decades. Correlative studies which link poor sleep to worse health cannot prove that it is the inadequate sleep which caused the problems, but studies in which human subjects undergo well-defined sleep deprivation for a defined number of hours coupled with EEGs, brain imaging studies and cognitive assessments are providing important insights into how poor sleep can affect brain function. The sleep researcher Matthew Walker at the University of California and his colleagues recently reviewed some of the key studies in sleep research and identified some of the major categories of brain function impairment as a consequence of sleep deprivation:

1.      Attention:

Several studies of human subjects have consistently shown that sleep deprivation leads to a significant decrease in the ability to pay attention to tasks. Some studies have kept subjects awake for 24 hours at a stretch whereas other studies merely restricted sleep to a few hours a night and monitored the performance. Importantly, one study that restricted sleep to less than 3 hours for one week was able to show that the attentiveness and performance of subjects recovered rapidly once the sleep-deprived subjects were allowed to sleep for 8 hours but it still did not return back to the levels of those without sleep deprivation. This means that the after-effects of sleep deprivation can linger for days even when we start sleeping normally.

2.      Memory:

The impairment of working memory (the temporary memory we use to make decisions and complete tasks) is another key feature of sleep deprivation. Brain imaging studies have been able to identify specific abnormalities in certain areas of the brain that are critical for the “working memory” function such as the dorsolateral prefrontal cortex and thus provide somewhat objective measures of cognitive impairment. Interestingly, placing magnetic coils around the head of sleep-deprived subjects to initiate TMS (transcranial magnetic stimulation) has been reported to help restore some of the loss of visual memory, however, Walker and colleagues note that the benefits of TMS in sleep deprivation are not always consistent and reproducible.

3.      Responding to negative stimuli

Sleep deprivation increases responses to negative stimuli such as fear. For example, when subjects who had one night of sleep deprivation were shown images of weapons, snakes or mutilations, their aversion responses were much stronger than those of control subjects. Hyper-responsiveness of the amygdala, the part of the brain which processes emotional reactions, is thought to be one major element in these exaggerated responses of sleep-deprived subjects.

Walker and colleagues note that not all changes seen in the brain imaging studies are necessarily detrimental. In fact, some of these changes may be adaptations that have evolved to help our brains cope with the stress of sleep deprivation. Even though significant progress has been made in sleep deprivation research, understanding differences between individuals in terms of how and why they respond differently to sleep deprivation, distinguishing the mechanisms of beneficial adaptations in brain function from detrimental responses and also developing new studies that study the effects of chronic sleep deprivation – one that occurs over a period of weeks and months and thus mimics real-life sleep deprivation – instead of the short-term acute sleep deprivation studies that are currently performed in the laboratory are major challenges for sleep researchers. Hopefully, advances in sleep research will lead to a better understanding of sleep health and ultimately also translate into sleep becoming an integral part of medical exams in order to address this burgeoning public health problem.

References

Watson NF, Badr MS, Belenky G, Bliwise DL, Buxton OM, Buysse D, Dinges DF, Gangwisch J, Grandner MA, Kushida C, Malhotra RK, Martin JL, Patel SR, Quan SF, Tasali E. Recommended amount of sleep for a healthy adult: a joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Society. J Clin Sleep Med 2015;11(6):591–592.

Liu Y, Wheaton AG, Chapman DP, Cunningham TJ, Lu H, Croft JB. Prevalence of Healthy Sleep Duration among Adults — United States, 2014. MMWR Morb Mortal Wkly Rep 2016;65:137–141

Krause AJ, Simon EB, Mander BA, Greer SM, Saletin JM, Goldstein-Piekarski AN, Walker MP. (2017). The sleep-deprived human brain. Nature Reviews Neuroscience

 

Note: An earlier version of this article was first published on the 3Quarksdaily blog.

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We Have Become Exhausted Slaves in a Culture of Positivity

We live in an era of exhaustion and fatigue, caused by an incessant compulsion to perform. This is one of the central tenets of the book “Müdigkeitsgesellschaft” (translatable as “The Fatigue Society” or “The Tiredness Society“) by the German philosopher Byung-Chul Han. Han is a professor at the Berlin Universität der Künste (University of the Arts) and one of the most widely read contemporary philosophers in Germany. He was born in Seoul where he studied metallurgy before he moved to Germany in the 1980s to pursue a career in philosophy. His doctoral thesis and some of his initial work in the 1990s focused on Heidegger but during the past decade, Han has written about broad range of topics regarding contemporary culture and society. “Müdigkeitsgesellschaft” was first published in 2010 and helped him attain a bit of a rock-star status in Germany despite his desire to avoid too much public attention – unlike some of his celebrity philosopher colleagues.

Fatigue

The book starts out with two biomedical metaphors to describe the 20th century and the emerging 21st century. For Han, the 20th century was an “immunological” era. He uses this expression because infections with viruses and bacteria which provoked immune responses were among the leading causes of disease and death and because the emergence of vaccinations and antibiotics helped conquer these threats. He then extends the “immunological” metaphor to political and societal events. Just like the immune system recognizes bacteria and viruses as “foreign” that needs to be eliminated to protect the “self”, the World Wars and the Cold War were also characterized by a clear delineation of “Us” versus “Them”. The 21stcentury, on the other hand, is a “neuronal” era characterized by neuropsychiatric diseases such as depression, attention deficit hyperactivity disorder (ADHD), burnout syndrome and borderline personality disorder. Unlike the diseases in the immunological era, where there was a clear distinction between the foreign enemy microbes that needed to be eliminated and the self, these “neuronal” diseases make it difficult to assign an enemy status. Who are the “enemies” in burnout syndrome or depression? Our environment? Our employers? Our own life decisions and choices? Are we at war with ourselves in these “neuronal” conditions? According to Han, this biomedical shift in diseases is mirrored by a political shift in a globalized world where it becomes increasingly difficult to define the “self” and the “foreign”. We may try to assign a “good guy” and “bad guy” status to navigate our 21st century but we also realize that we are so interconnected that these 20th century approaches are no longer applicable.

The cell biologist in me cringed when I read Han’s immunologic and neuronal metaphors. Yes, it is true that successfully combatting infectious diseases constituted major biomedical victories in the 20th century but these battles are far from over. The recent Ebola virus scare, the persistence of malaria resistance, the under-treatment of HIV and the emergence of multi-drug resistant bacteria all indicate that immunology and infectious disease will play central roles in the biomedical enterprise of the 21st century. The view that the immune system clearly distinguishes between “self” and “foreign” is also overly simplistic because it ignores that autoimmune diseases, many of which are on the rise and for which we still have very limited treatment options, are immunological examples of where the “self” destroys itself. Even though I agree that neuroscience will likely be the focus of biomedical research, it seems like an odd choice to select a handful of psychiatric illnesses as representing the 21st century while ignoring major neuronal disorders such as Alzheimer’s dementia, stroke or Parkinson’s disease. He also conflates specific psychiatric illnesses with the generalized increase in perceived fatigue and exhaustion.

Once we move past these ill- chosen biomedical examples, Han’s ideas become quite fascinating. He suggests that the reason why we so often feel exhausted and fatigued is because we are surrounded by a culture of positivity. At work, watching TV at home or surfing the web, we are inundated by not-so-subtle messages of what we can do. Han quotes the example of the “Yes We Can” slogan from the Obama campaign. “Yes We Can” exudes positivity by suggesting that all we need to do is try harder and that there may be no limits to what we could achieve. The same applies to the Nike “Just Do It” slogan and the thousands of self-help books published each year which reinforce the imperative of positive thinking and positive actions.

Here is the crux of Han’s thesis. “Yes We Can” sounds like an empowering slogan, indicating our freedom and limitless potential. But according to Han, this is an illusory freedom because the message enclosed within “Yes We Can” is “Yes We Should”. Instead of living in a Disziplinargesellschaft(disciplinary society) of the past where our behavior was clearly regulated by societal prohibitions and commandments, we now live in a Leistungsgesellschaft (achievement society) in which we voluntarily succumb to the pressure of achieving. The Leistungsgesellschaft is no less restrictive than the Disziplinargesellschaft. We are no longer subject to exogenous prohibitions but we have internalized the mandates of achievement, always striving to do more. We have become slaves to the culture of positivity, subjugated by the imperative “Yes, We Should”. Instead of carefully contemplating whether or not to pursue a goal, the mere knowledge that we could achieve it forces us to strive towards that goal. Buying into the “Yes We Can” culture chains us to a life of self-exploitation and we are blinded by passion and determination until we collapse. Han uses the sad German alliteration “Erschöpfung, Ermüdung und Erstickung” (“exhaustion, fatigue and suffocation”) to describe the impact that an excess of positivity has once we forgo our ability to say “No!” to the demands of the achievement society. We keep on going until our minds and bodies shut down and this is why we live in a continuous state of exhaustion and fatigue. Han does not view multitasking as a sign of civilizational progress. Multitasking is an indicator of regression because it results in a broad but rather superficial state of attention and thus prevents true contemplation

It is quite easy for us to relate to Han’s ideas at our workplace. Employees with a “can-do” attitude are praised but you will rarely see a plaque awarded to commemorate an employee’s “can-contemplate” attitude. In an achievement society, employers no longer have to exploit us because we willingly take on more and more tasks to prove our own self-worth.

While reading Han’s book, I was reminded of a passage in Bertrand Russell’s essay “In Praise of Idleness” in which he extols the virtues of reducing our workload to just four hours a day:

In a world where no one is compelled to work more than four hours a day, every person possessed of scientific curiosity will be able to indulge it, and every painter will be able to paint without starving, however excellent his pictures may be. Young writers will not be obliged to draw attention to themselves by sensational pot-boilers, with a view to acquiring the economic independence needed for monumental works, for which, when the time at last comes, they will have lost the taste and capacity. Men who, in their professional work, have become interested in some phase of economics or government, will be able to develop their ideas without the academic detachment that makes the work of university economists often seem lacking in reality. Medical men will have the time to learn about the progress of medicine, teachers will not be exasperatedly struggling to teach by routine methods things which they learnt in their youth, which may, in the interval, have been proved to be untrue.

Above all, there will be happiness and joy of life, instead of frayed nerves, weariness, and dyspepsia. The work exacted will be enough to make leisure delightful, but not enough to produce exhaustion. Since men will not be tired in their spare time, they will not demand only such amusements as are passive and vapid. At least one per cent will probably devote the time not spent in professional work to pursuits of some public importance, and, since they will not depend upon these pursuits for their livelihood, their originality will be unhampered, and there will be no need to conform to the standards set by elderly pundits. But it is not only in these exceptional cases that the advantages of leisure will appear. Ordinary men and women, having the opportunity of a happy life, will become more kindly and less persecuting and less inclined to view others with suspicion.

While Russell’s essay proposes reduction of work hours as a solution, Han’s critique of the achievement society and its impact on generalized fatigue and malaise is not limited to our workplace. By accepting the mandate of continuous achievement and hyperactivity, we apply this approach even to our leisure time. Whether it is counting the steps we walk with our fitness activity trackers or competitively racking up museum visits as a tourist, our obsession with achievement permeates all aspects of our lives. Is there a way out of this vicious cycle of excess positivity and persistent exhaustion? We need to be mindful of our right to refuse. Instead of piling on tasks for ourselves during work and leisure we need to recognize the value and strength of saying “No”. Han introduces the concept of “heilende Müdigkeit” (healing tiredness), suggesting that there is a form of tiredness that we should welcome because it is an opportunity for rest and regeneration. Weekend days are often viewed as days reserved for chores and leisure tasks that we are unable to pursue during regular workdays. By resurrecting the weekend as the time for actual rest, idleness and contemplation we can escape from the cycle of exhaustion. We have to learn not-doing in a world obsessed with doing.

Notes: An earlier version of this article was first published on the 3Quarksdaily Blog. Müdigkeitsgesellschaft was translated into English in 2015 and is available as “The Burnout Society” by Stanford University Press.

ResearchBlogging.org

Byung-Chul Han (2015). The Burnout Society Stanford University Press

Feel Our Pain: Empathy and Moral Behavior

“It’s empathy that makes us help other people. It’s empathy that makes us moral.” The economist Paul Zak casually makes this comment in his widely watched TED talk about the hormone oxytocin, which he dubs the “moral molecule”. Zak quotes a number of behavioral studies to support his claim that oxytocin increases empathy and trust, which in turn increases moral behavior. If all humans regularly inhaled a few puffs of oxytocin through a nasal spray, we could become more compassionate and caring. It sounds too good to be true. And recent research now suggests that this overly simplistic view of oxytocin, empathy and morality is indeed too good to be true.

Hands

Many scientific studies support the idea that oxytocin is a major biological mechanism underlying the emotions of empathy and the formation of bonds between humans. However, inferring that these oxytocin effects in turn make us more moral is a much more controversial statement. In 2011, the researcher Carsten De Dreu and his colleagues at the University of Amsterdam in the Netherlands published the study Oxytocin promotes human ethnocentrism which studied indigenous Dutch male study subjects who in a blinded fashion self-administered either nasal oxytocin or a placebo spray. The subjects then answered questions and performed word association tasks after seeing photographic images of Dutch males (the “in-group”) or images of Arabs and Germans, the “out-group” because prior surveys had shown that the Dutch public has negative views of both Arabs/Muslims and Germans. To ensure that the subjects understood the distinct ethnic backgrounds of the target people shown in the images, they were referred to typical Dutch male names, German names (such as Markus and Helmut) or Arab names (such as Ahmed and Youssef).

Oxytocin increased favorable views and word associations but only towards in-group images of fellow Dutch males. The oxytocin treatment even had the unexpected effect of worsening the views regarding Arabs and Germans but this latter effect was not quite statistically significant. Far from being a “moral molecule”, oxytocin may actually increase ethnic bias in society because it selectively enhances certain emotional bonds. In a subsequent study, De Dreu then addressed another aspect of the purported link between oxytocin and morality by testing the honesty of subjects. The study Oxytocin promotes group-serving dishonesty showed that oxytocin increased cheating in study subjects if they were under the impression that dishonesty would benefit their group. De Dreu concluded that oxytocin does make us less selfish and care more about the interest of the group we belong to.

These recent oxytocin studies not only question the “moral molecule” status of oxytocin but raise the even broader question of whether more empathy necessarily leads to increased moral behavior, independent of whether or not it is related to oxytocin. The researchers Jean Decety and Jason Cowell at the University of Chicago recently analyzed the scientific literature on the link between empathy and morality in their commentary Friends or Foes: Is Empathy Necessary for Moral Behavior?, and find that the relationship is far more complicated than one would surmise. Judges, police officers and doctors who exhibit great empathy by sharing in the emotional upheaval experienced by the oppressed, persecuted and severely ill always end up making the right moral choices – in Hollywood movies. But empathy in the real world is a multi-faceted phenomenon and we use this term loosely, as Decety and Cowell point out, without clarifying which aspect of empathy we are referring to.

Decety and Cowell distinguish at least three distinct aspects of empathy:

1. Emotional sharing, which refers to how one’s emotions respond to the emotions of those around us. Empathy enables us to “feel” the pain of others and this phenomenon of emotional sharing is also commonly observed in non-human animals such as birds or mice.

2. Empathic concern, which describes how we care for the welfare of others. Whereas emotional sharing refers to how we experience the emotions of others, empathic concern motivates us to take actions that will improve their welfare. As with emotional sharing, empathic concern is not only present in humans but also conserved among many non-human species and likely constitutes a major evolutionary advantage.

3. Perspective taking, which – according to Decety and Cowell – is the ability to put oneself into the mind of another and thus imagine what they might be thinking or feeling. This is a more cognitive dimension of empathy and essential for our ability to interact with fellow human beings. Even if we cannot experience the pain of others, we may still be able to understand or envision how they might be feeling. One of the key features of psychopaths is their inability to experience the emotions of others. However, this does not necessarily mean that psychopaths are unable to cognitively imagine what others are thinking. Instead of labeling psychopaths as having no empathy, it is probably more appropriate to specifically characterize them as having a reduced capacity to share in the emotions while maintaining an intact capacity for perspective-taking.

In addition to the complexity of what we call “empathy”, we need to also understand that empathy is usually directed towards specific individuals and groups. De Dreu’s studies demonstrated that oxytocin can make us more pro-social as long as it benefits those who we feel belong to our group but not necessarily those outside of our group. The study Do you feel my pain? Racial group membership modulates empathic neural responses by Xu and colleagues at Peking University used fMRI brain imaging in Chinese and Caucasian study subjects and measured their neural responses to watching painful images. The study subjects were shown images of either a Chinese or a Caucasian face. In the control condition, the depicted image showed a face being poked with a cotton swab. In the pain condition, study subjects were shown a face of a person being poked with a needle attached to syringe. When the researchers measured the neural responses with the fMRI, they found significant activation in the anterior cingulate cortex (ACC) which is part of the neural pain circuit, both for pain we experience ourselves but also for empathic pain we experience when we see others in pain. The key finding in Xu’s study was that ACC activation in response to seeing the painful image was much more profound when the study subject and the person shown in the painful image belonged to the same race.

As we realize that the neural circuits and hormones which form the biological basis of our empathy responses are so easily swayed by group membership then it becomes apparent why increased empathy does not necessarily result in behavior consistent with moral principles. In his essay “Against Empathy“, the psychologist Paul Bloom also opposes the view that empathy should form the basis of morality and that we should unquestioningly elevate empathy to virtue for all:

“But we know that a high level of empathy does not make one a good person and that a low level does not make one a bad person. Being a good person likely is more related to distanced feelings of compassion and kindness, along with intelligence, self-control, and a sense of justice. Being a bad person has more to do with a lack of regard for others and an inability to control one’s appetites.”

I do not think that we can dismiss empathy as a factor in our moral decision-making. Bloom makes a good case for distanced compassion and kindness that does not arise from the more visceral emotion of empathy. But when we see fellow humans and animals in pain, then our initial biological responses are guided by empathy and anger, not the more abstract concept of distanced compassion. What we need is a better scientific and philosophical understanding of what empathy is. Empathic perspective-taking may be a far more robust and reliable guide for moral decision-making than empathic emotions. Current scientific studies on empathy often measure it as an aggregate measure without teasing out the various components of empathy. They also tend to underestimate that the relative contributions of the empathy components (emotion, concern, perspective-taking) can vary widely among cultures and age groups. We need to replace overly simplistic notions such as oxytocin = moral molecule or empathy = good with a more refined view of the complex morality-empathy relationship guided by rigorous science and philosophy.

 

References:

De Dreu, C. K., Greer, L. L., Van Kleef, G. A., Shalvi, S., & Handgraaf, M. J. (2011). Oxytocin promotes human ethnocentrismProceedings of the National Academy of Sciences, 108(4), 1262-1266.

Decety, J., & Cowell, J. M. (2014). Friends or Foes: Is Empathy Necessary for Moral Behavior?Perspectives on Psychological Science, 9(5), 525-537.

Shalvi, S., & De Dreu, C. K. (2014). Oxytocin promotes group-serving dishonestyProceedings of the National Academy of Sciences, 111(15), 5503-5507.

Xu, X., Zuo, X., Wang, X., & Han, S. (2009). Do you feel my pain? Racial group membership modulates empathic neural responsesThe Journal of Neuroscience, 29(26), 8525-8529.

 

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Note: An earlier version of this article was first published on the 3Quarksdaily blog.

 

ResearchBlogging.org

 

 

 

 

De Dreu, C., Greer, L., Van Kleef, G., Shalvi, S., & Handgraaf, M. (2011). Oxytocin promotes human ethnocentrism Proceedings of the National Academy of Sciences, 108 (4), 1262-1266 DOI: 10.1073/pnas.1015316108

 

Decety J, & Cowell JM (2014). Friends or Foes: Is Empathy Necessary for Moral Behavior? Perspectives on psychological science : a journal of the Association for Psychological Science, 9 (5), 525-37 PMID: 25429304

 

Shalvi S, & De Dreu CK (2014). Oxytocin promotes group-serving dishonesty. Proceedings of the National Academy of Sciences of the United States of America, 111 (15), 5503-7 PMID: 24706799

 

Xu X, Zuo X, Wang X, & Han S (2009). Do you feel my pain? Racial group membership modulates empathic neural responses. The Journal of neuroscience : the official journal of the Society for Neuroscience, 29 (26), 8525-9 PMID: 19571143

Typical Dreams: A Comparison of Dreams Across Cultures

But I, being poor, have only my dreams;

I have spread my dreams under your feet;

Tread softly because you tread on my dreams.

                                    William Butler Yeats – from “Aedh Wishes for the Cloths of Heaven

 

Maze

Have you ever wondered how the content of your dreams differs from that of your friends? How about the dreams of people raised in different countries and cultures? It is not always easy to compare dreams of distinct individuals because the content of dreams depends on our personal experiences. This is why dream researchers have developed standardized dream questionnaires in which common thematic elements are grouped together. These questionnaires can be translated into various languages and used to survey and scientifically analyze the content of dreams. Open-ended questions about dreams might elicit free-form, subjective answers which are difficult to categorize and analyze. Therefore, standardized dream questionnaires ask study subjects “Have you ever dreamed of . . .” and provide research subjects with a list of defined dream themes such as being chased, flying or falling.

Dream researchers can also modify the questionnaires to include additional questions about the frequency or intensity of each dream theme and specify the time frame that the study subjects should take into account. For example, instead of asking “Have you ever dreamed of…”, one can prompt subjects to focus on the dreams of the last month or the first memory of ever dreaming about a certain theme. Any such subjective assessment of one’s dreams with a questionnaire has its pitfalls. We routinely forget most of our dreams and we tend to remember the dreams that are either the most vivid or frequent, as well as the dreams which we may have discussed with friends or written down in a journal. The answers to dream questionnaires may therefore be a reflection of our dream memory and not necessarily the actual frequency of prevalence of certain dream themes. Furthermore, standardized dream questionnaires are ideal for research purposes but may not capture the complex and subjective nature of dreams. Despite these pitfalls, research studies using dream questionnaires provide a fascinating insight into the dream world of large groups of people and identify commonalities or differences in the thematic content of dreams across cultures.

The researcher Calvin Kai-Ching Yu from the Hong Kong Shue Yan University used a Chinese translation of a standardized dream questionnaire and surveyed 384 students at the University of Hong Kong (mostly psychology students; 69% female, 31% male; mean age 21). Here are the results:

Ten most prevalent dream themes in a sample of Chinese students according to Yu (2008):

  1. Schools, teachers, studying (95%)
  2. Being chased or pursued (92 %)
  3. Falling (87 %)
  4. Arriving too late, e.g., missing a train (81 %)
  5. Failing an examination (79 %)
  6. A person now alive as dead (75%)
  7. Trying again and again to do something (74%)
  8. Flying or soaring through the air (74%)
  9. Being frozen with fright (71 %)
  10. Sexual experiences (70%)

The most prevalent theme was “Schools, teachers, studying“. This means that 95% of the study subjects recalled having had dreams related to studying, school or teachers at some point in their lives, whereas only 70% of the subjects recalled dreams about sexual experiences. The subjects were also asked to rank the frequency of the dreams on a 5-point scale (0 = never, 1=seldom, 2= sometimes, 3= frequently, 4= very frequently). For the most part, the most prevalent dreams were also the most frequent ones. Not only did nearly every subject recall dreams about schools, teachers or studying, this theme also received an average frequency score of 2.3, indicating that for most individuals this was a recurrent dream theme – not a big surprise in university students. On the other hand, even though the majority of subjects (57%) recalled dreams of “being smothered, unable to breathe“, its average frequency rating was low (0.9), indicating that this was a rare (but probably rather memorable) dream.

How do the dreams of the Chinese students compare to their counterparts in other countries?

Michael Schredl and his colleagues used a similar questionnaire to study the dreams of German university students (nearly all psychology students; 85% female, 15% male; mean age 24) with the following results:

Ten most prevalent dream themes in a sample of German students according to Schredl and colleagues (2004):

  1. Schools, teachers, studying (89 %)
  2. Being chased or pursued (89%)
  3. Sexual experiences (87 %)
  4. Falling (74 %)
  5. Arriving too late, e.g., missing a train (69 %)
  6. A person now alive as dead (68 %)
  7. Flying or soaring through the air (64%)
  8. Failing an examination (61 %)
  9. Being on the verge of falling (57 %)
  10. Being frozen with fright (56 %)

There is a remarkable overlap in the top ten list of dream themes among Chinese and German students. Dreams about school and about being chased are the two most prevalent themes for Chinese and German students. One key difference is that dreams about sexual experiences are recalled more commonly among German students.

Tore Nielsen and his colleagues administered a dream questionnaire to students at three Canadian universities, thus obtaining data on an even larger study population (over 1,000 students).

Ten most prevalent dream themes in a sample of Canadian students according to Nielsen and colleagues (2003):

  1. Being chased or pursued (82 %)
  2. Sexual experiences (77 %)
  3. Falling (74 %)
  4. Schools, teachers, studying (67 %)
  5. Arriving too late, e.g., missing a train (60 %)
  6. Being on the verge of falling (58 %)
  7. Trying again and again to do something (54 %)
  8. A person now alive as dead (54 %)
  9. Flying or soaring through the air (48%)
  10. Vividly sensing . . . a presence in the room (48 %)

It is interesting that dreams about school or studying were the most common theme among Chinese and German students but do not even make the top-three list among Canadian students. This finding is perhaps also mirrored in the result that dreams about failing exams are comparatively common in Chinese and German students, but are not found in the top-ten list among Canadian students.

At first glance, the dream content of German students seems to be somehow a hybrid between those of Chinese and Canadian students. Chinese and German students share a higher prevalence of academia-related dreams, whereas sexual dreams are among the most prevalent dreams for both Canadians and Germans. However, I did notice an interesting aberrancy. Chinese and Canadian students dream about “Trying again and again to do something” – a theme which is quite rare among German students. I have simple explanation for this (possibly influenced by the fact that I am German): Germans get it right the first time which is why they do not dream about repeatedly attempting the same task.

The strength of these three studies is that they used similar techniques to assess dream content and evaluated study subjects with very comparable backgrounds: Psychology students in their early twenties. This approach provides us with the unique opportunity to directly compare and contrast the dreams of people who were raised on three continents and immersed in distinct cultures and languages. However, this approach also comes with a major limitation. We cannot easily extrapolate these results to the general population. Dreams about studying and school may be common among students but they are probably rare among subjects who are currently holding a full-time job or are retired. University students are an easily accessible study population but they are not necessarily representative of the society they grow up in. Future studies which want to establish a more comprehensive cross-cultural comparison of dream content should probably attempt to enroll study subjects of varying ages, professions, educational and socio-economic backgrounds.

Despite its limitation, the currently available data on dream content comparisons across countries does suggest one important message: People all over the world have similar dreams.

 

References:

Yu, Calvin Kai-Ching. “Typical dreams experienced by Chinese people.” Dreaming 18.1 (2008): 1-10.

Nielsen, Tore A., et al. “The Typical Dreams of Canadian University Students.” Dreaming 13.4 (2003): 211-235.

Schredl, Michael, et al. “Typical dreams: stability and gender differences.” The Journal of psychology 138.6 (2004): 485-494.

Note: An earlier version of this article was first published on 3Quarksdaily.

ResearchBlogging.org

Yu, C. (2008). Typical dreams experienced by Chinese people. Dreaming, 18 (1), 1-10 DOI: 10.1037/1053-0797.18.1.1
Nielsen, T., Zadra, A., Simard, V., Saucier, S., Stenstrom, P., Smith, C., & Kuiken, D. (2003). The Typical Dreams of Canadian University Students. Dreaming, 13 (4), 211-235 DOI: 10.1023/B:DREM.0000003144.40929.0b

Schredl M, Ciric P, Götz S, & Wittmann L (2004). Typical dreams: stability and gender differences. The Journal of psychology, 138 (6), 485-94 PMID: 15612605

The Metered Brain: Temporal Structure and Processing of Poetry

I recently wrote a short essay for 3Quarksdaily on the three second rule of temporal perception and processing in the human brain. It is comparatively easy to measure the thresholds that our brain uses to create temporal structure, i.e. the minimum time interval required to correctly tell apart the sequence of brief sounds or images. It lies somewhere in the range of 30 milliseconds to 60 milliseconds. If healthy subjects hear two auditory clicks (one in the right ear and one in the left ear) which are only 10 milliseconds apart, they may be able to identify them as two distinct stimuli, but they may not be able to say which one came first.

Temporal integration, on the other hand, refers to combining sensory information and creating the sense of a subjective present or the perception of a “now”. It is not possible to directly measure it, but many observational studies point to a “three second rule” of temporal integration in the brain. One of these studies involved the analysis of poetic meter and was conducted by the chairman of the department in which I used to work when I was a student. The study found that the average time it takes to recite individual verses of poems from all around the world is approximately three seconds. Since each verse (the authors use the more generic term “LINE” to accomodate poems which use a different orthrographic notation or which allow for pauses when reciting long verses) is considered to be an independent unit that is intended to evoke certain poetic “moments”, the authors surmise that the global convergence of verse length may be due to the fact that our brain is most comfortable with three-second intervals to create the sensation of the “now”. This is obviously anecdotal and observational, and not a definitive finding, but it is still fascinating. It does not “prove” that our brain perceives the “now” in three second intervals, but when combined with other cognitive studies of temporal integration, it supports the notion that three seconds may be an important temporal unit for our brain.

The complete essay can be found here: http://www.3quarksdaily.com/3quarksdaily/2013/07/three-seconds-poems-cubes-and-the-brain.html.

You should consider reading some of the original references that are linked in my 3Quraksdaily essay, such as the classic study published in the Poetry magazine, which is (thankfully) open access and can be read by everyone. It is a remarkable example of how a collaboration between a cognitive scientist (my former chairman) and a poet which won a prestigious poetry award when it was published in 1983.