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.


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.

Dismantle the Poverty Trap by Nurturing Community Trust

Would you rather receive $100 today or wait for a year and then receive $150? The ability to delay immediate gratification for a potentially greater payout in the future is associated with greater wealth. Several studies have shown that the poor tend to opt for immediate rewards even if they are lower, whereas the wealthy are willing to wait for greater rewards. One obvious reason for this difference is the immediate need for money. If food has to be purchased and electricity or water bills have to be paid, then the instant “reward” is a matter of necessity. Wealthier people can easily delay the reward because their basic needs for food, shelter and clothing are already met.

Unfortunately, escaping from poverty often requires the ability to delay gratification for a greater payout in the future. Classic examples are the pursuit of higher education and the acquisition of specialized professional skills which can lead to better-paying jobs in the future. Attending vocational school, trade school or college paves the way for higher future wages, but one has to forego income during the educational period and even incur additional debt by taking out educational loans. Another example is of delayed gratification is to invest capital – whether it is purchasing a farming tool that increases productivity or investing in the stock market – which in turn can yield greater pay-out. However, if the poor are unable to pursue more education or make other investments that will increase their income, they remain stuck in a vicious cycle of increasing poverty.

Understanding the precise reasons for why people living in poverty often make decisions that seem short-sighted, such as foregoing more education or taking on high-interest short-term loans, is the first step to help them escape poverty. The obvious common-sense fix is to ensure that the basic needs of all citizens – food, shelter, clothing, health and personal safety – are met, so that they no longer have to use all new funds for survival. This is obviously easier in the developed world, but it is not a trivial matter considering that the USA – supposedly the richest country in the world – has an alarmingly high poverty rate. It is estimated that more than 40 million people in the US live in poverty, fearing hunger and eviction from their homes. But just taking care of these basic needs may not be enough to help citizens escape poverty. A recent research study by Jon Jachimowicz at Columbia University and his colleagues investigated “myopic” (short-sighted) decision-making of people with lower income and identified an important new factor: community trust.

The researchers first used an online questionnaire (647 participants) to assess trust and asked participants to choose between a payoff in the near future that is smaller and a larger pay-off in the distant future. They also measured community trust by asking participants to agree or disagree with statements such as “There are advantages to living in my neighborhood” or I would like my child(ren) to be raised in the neighborhood I currently live in”. They found that lower income participants were more likely to act in a short-sighted manner if they had low levels of trust in their communities. In a second online experiment, the researchers recruited roughly 100 participants from each state in the US and assessed their community trust levels. They then obtained real-world data on payday loans – a sign of very short-sighted financial decision-making because people take out cash advances at extraordinarily high interest rates that have to be paid back when they get their paycheck – for each state. They found that the average community trust for each state was related to the use of payday loans. In states with high average community trust ratings, people were less likely to take out these payday loans, and this trend remained even when the researchers took into account unemployment rates and savings rates for each state.

Even though these findings all pointed to a clear relationship between community trust and sound financial decision-making, the results did not prove that increased community trust is an underlying cause that helps improve the soundness of financial decisions. To test this relationship in a real-world setting, the researchers conducted a study in rural Bangladesh by collaborating with an international development organization based in Bangladesh. The vast majority of participants in this study were poor even by Bangladeshi standards, earning less than $1/day per household member. The researchers adapted the community trust questionnaire and the assessment of financial decision-making for the rural population, with live interviewers asking the questions and filling out the responses for the participants. After assessing community trust and the willingness to delay financial rewards for greater payouts in the future, half of the participants received a two year intervention to increase community trust. This intervention involved volunteers from the community that acted as intermediaries between the local government and the rural population, providing input into local governance and community-level decisions (for example in the distribution of social benefits and the allocation of funds for development projects).

At the end of the two year period, participants who had received the community intervention showed significant increases in their community trust levels and they also improved their financial decision-making. They were more likely to forego immediate lower financial rewards for greater future rewards when compared to the villagers who did not receive any special intervention.

By combining correlational data from the United States with an actual real-world intervention to build community trust, the researchers show how important it is to build trust when we want to help fellow humans escape the “poverty trap“. This is just an initial study with a limited group of participants and a narrow intervention that needs to be replicated in other societies and with long-term observation of the results to see how persistent the effects are. But the results should make all of us realize that just creating “jobs, jobs, jobs” is not enough. We need to invest in the infrastructures of communities and help citizens realize that they are respected members of society with a voice. Empowering individuals and ensuring their safety, dignity and human rights are necessary steps if we are serious about battling poverty.


Jachimowicz, J. M., Chafik, S., Munrat, S., Prabhu, J. C., & Weber, E. U. (2017). Community trust reduces myopic decisions of low-income individuals. Proceedings of the National Academy of Sciences, 201617395.

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

Jachimowicz, J., Chafik, S., Munrat, S., Prabhu, J., & Weber, E. (2017). Community trust reduces myopic decisions of low-income individuals Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1617395114

Are American Professors More Responsive to Requests Made by White Male Students?

Less than one fifth of PhD students in the United States will be able to pursue tenure track academic faculty careers once they graduate from their program. Reduced federal funding for research and dwindling support from the institutions for their tenure-track faculty are some of the major reasons for why there is such an imbalance between the large numbers of PhD graduates and the limited availability of academic positions. Upon completing the program, PhD graduates have to consider non-academic job opportunities such as in the industry, government agencies and non-profit foundations but not every doctoral program is equally well-suited to prepare their graduates for such alternate careers. It is therefore essential for prospective students to carefully assess the doctoral program they want to enroll in and the primary mentor they would work with. The best approach is to proactively contact prospective mentors, meet with them and learn about the research opportunities in their group but also discuss how completing the doctoral program would prepare them for their future careers.


The vast majority of professors will gladly meet a prospective graduate student and discuss research opportunities as well as long-term career options, especially if the student requesting the meeting clarifies the goal of the meeting. However, there are cases when students wait in vain for a response. Is it because their email never reached the professor because it got lost in the internet ether or a spam folder? Was the professor simply too busy to respond? A research study headed by Katherine Milkman from the University of Pennsylvania suggests that the lack of response from the professor may in part be influenced by the perceived race or gender of the student.

Milkman and her colleagues conducted a field experiment in which 6,548 professors at the leading US academic institutions (covering 89 disciplines) were contacted via email to meet with a prospective graduate student. Here is the text of the email that was sent to each professor.

Subject Line: Prospective Doctoral Student (On Campus Next


Dear Professor [surname of professor inserted here],

I am writing you because I am a prospective doctoral student with considerable interest in your research. My plan is to apply to doctoral programs this coming Fall, and I am eager to learn as much as I can about research opportunities in the meantime.

I will be on campus next Monday, and although I know it is short notice, I was wondering if you might have 10 minutes when you would be willing to meet with me to briefly talk about your work and any possible opportunities for me to get involved in your research. Any time that would be convenient for you would be fine with me, as meeting with you is my first priority during this campus visit.

 Thank you in advance for your consideration.


[Student’s full name inserted here]

As a professor who frequently receives emails from people who want to work in my laboratory, I feel that the email used in the research study was extremely well-crafted. The student only wants a brief meeting to explore potential opportunities without trying to extract any specific commitment from the professor. The email clearly states the long-term goal – applying to doctoral programs. The tone is also very polite and the student expresses willingness of the prospective student to a to the professor’s schedule. Each email was also personally addressed with the name of the contacted faculty member.

Milkman’s research team then assessed whether the willingness of the professors to respond depended on the gender or ethnicity of the prospective student.  Since this was an experiment, the emails and student names were all fictional but the researchers generated names which most readers would clearly associate with a specific gender and ethnicity.

Here is a list of the names they used:

White male names:  Brad Anderson, Steven Smith

White female names:  Meredith Roberts, Claire Smith

Black male names: Lamar Washington, Terell Jones

Black female names: Keisha Thomas, Latoya Brown

Hispanic male names: Carlos Lopez, Juan Gonzalez

Hispanic female names: Gabriella Rodriguez, Juanita Martinez

Indian male names: Raj Singh, Deepak Patel

Indian female names: Sonali Desai, Indira Shah

Chinese Male names; Chang Huang, Dong Lin

Chinese female names: Mei Chen, Ling Wong

The researchers assessed whether the professors responded (either by agreeing to meet or providing a reason for why they could not meet) at all or whether they simply ignored the email and whether the rate of response depended on the ethnicity/gender of the student.

The overall response rate of the professors ranged from about 60% to 80%, depending on the research discipline as well as the perceived ethnicity and gender of the prospective student. When the emails were signed with names suggesting a white male background of the student, professors were far less likely to ignore the email when compared to those signed with female names or names indicating an ethnic minority background. Professors in the business sciences showed the strongest discrimination in their response rates. They ignored only 18% of emails when it appeared that they had been written by a white male and ignored 38% of the emails if they were signed with names indicating a female gender or ethnic minority background. Professors in the education disciplines ignored 21% of emails with white male names versus 35% with female or minority names. The discrimination gaps in the health sciences (33% vs 43%) and life sciences (32% vs 39%) were smaller but still significant, whereas there was no statistical difference in the humanities professor response rates. Doctoral programs in the fine arts were an interesting exception where emails from apparent white male students were more likely to be ignored (26%) than those of female or minority candidates (only 10%).

The discrimination primarily occurred at the initial response stage. When professors did respond, there was no difference in terms of whether they were able to make time for the student. The researchers also noted that responsiveness discrimination in any discipline was not restricted to one gender or ethnicity. In business doctoral programs, for example, professors were most likely to ignore emails with black female names and Indian male names. Significant discrimination against white female names (when compared to white males names) predicted an increase in discrimination against other ethnic minorities. Surprisingly, the researchers found that having higher representation of female and minority faculty at an institution did not necessarily improve the responsiveness towards requests from potential female or minority students.

This carefully designed study with a large sample size of over 6,500 professors reveals the prevalence of bias against women and ethnic minorities at the top US institutions. This bias may be so entrenched and subconscious that it cannot be remedied by simply increasing the percentage of female or ethnic minority professors in academia. Instead, it is important that professors understand that they may be victims of these biases even if they do not know it. Something as simple as deleting an email from a prospective student because we think that we are too busy to respond may be indicative of an insidious gender or racial bias that we need to understand and confront. Increased awareness and introspection as well targeted measures by institutions are the important first steps to ensure that students receive the guidance and mentorship they need, independent of their gender or ethnic background.


Milkman KL, Akinola M, Chugh D. (2015). What Happens Before? A Field Experiment Exploring How Pay and Representation Differentially Shape Bias on the Pathway Into Organizations. Journal of Applied Psychology, 100(6), 1678–1712.

Note: An earlier version of this post was first published on the 3Quarksdaily Blog.

Milkman KL, Akinola M, & Chugh D (2015). What happens before? A field experiment exploring how pay and representation differentially shape bias on the pathway into organizations. The Journal of applied psychology, 100 (6), 1678-712 PMID: 25867167

Imagine: Listening to Songs Which Make Us More Generous

It does not come as a surprise that background music in a café helps create the ambience and affects how much customers enjoy sipping their cappuccinos. But recent research suggests that the choice of lyrics can even impact the social behavior of customers. The researcher Nicolas Ruth and his colleagues from the University of Würzburg (Bavaria, Germany) assembled a playlist of 18 songs with pro-social lyrics which they had curated by surveying 74 participants in an online questionnaire as to which songs conveyed a pro-social message. Examples of pro-social songs most frequently nominated by the participants included “Imagine” by John Lennon or “Heal the World” by Michael Jackson. The researchers then created a parallel playlist of 18 neutral songs by the same artists in order to truly discern the impact of the pro-social lyrics.


Here is an excerpt of both playlists

Artist                                    Pro-social playlist               Neutral playlist

P!nk                                         Dear Mr. President                    Raise Your Glass

John Lennon                           Imagine                                     Stand By Me

Michael Jackson                    Heal the World                         Dirty Diana

Nicole                                      Ein bisschen Frieden               Alles nur für dich

Pink Floyd                               Another Brick in the Wall      Wish You Were Here

Scorpions                                Wind of Change                        Still Loving You

Wiz Khalifa                              See You Again                          Black and Yellow

The researchers then arranged for either the neutral or the pro-social playlist to be played in the background in a Würzburg café during their peak business hours and to observe the behavior of customers. The primary goal of the experiment was to quantify the customers’ willingness to pay a surcharge of 0.30 Euros for fair trade coffee instead of regular coffee. Fair trade coffee is more expensive because it is obtained through organizations which offer better trading conditions to coffee bean farmers, prohibit child labor and support sustainable farming practices. Information about fair trade coffee was presented on a blackboard in the center of the café so that all customers would walk past it and the server was trained by the researchers to offer the fair trade surcharge in a standardized manner. The server also waited for a minimum of six minutes before taking the orders of guests so that they would be able to hear at least two songs in the background. During the observation period, 123 customers heard the prosocial playlist whereas 133 heard the neutral playlist.

The effect of this brief exposure to prosocial songs was quite remarkable. The percentage of customers who opted for the more expensive fair trade coffee option doubled when they head prosocial songs! Only 18% of customers hearing the neutral playlist were willing to pay the extra 0.30 Euros – even though they had also seen the information board about the benefits of fair trade coffee – but 38% of the customers hearing prosocial songs opted for the fair trade option.

Interestingly, hearing prosocial songs did not affect the tipping behavior of the customers. Independent of what music was playing in the background, customers tipped the server roughly 12% of the bill. This is in contrast to a prior study conducted in a French restaurant in which hearing prosocial songs increased the tipping behavior. One factor explaining the difference could be the manner by which the songs were selected. The French study specifically created a playlist of prosocial songs with French lyrics whereas the Würzburg playlist contained mostly English-language songs, often with global themes such as world peace, brotherhood and abolishing boundaries. Supporting fair trade may be more consistent with the images evoked by these global-themed songs than increased tipping of a server in Germany. It is also important to note that servers or waiters in Germany are comparatively well-compensated by restaurants and cafés, therefore they do not really depend on their income from tips.

The Würzburg experiment raises some intriguing questions about how music – either consciously or subconsciously – affects our immediate decision-making. The researchers went to great lengths to minimize confounding factors by matching up songs from the same artists in both playlists. Their work is also one of the first examples of a field study in a real-world setting because prior studies linking music and pro-social behavior have been mostly conducted in laboratory settings where pro-social behavior is experimentally simulated. But one also needs to consider some caveats before generalizing the results of the study.

Würzburg is a university town where students represent a significant proportion of the population. The researchers estimated that more than 40% of the customers were in their 20s, consistent with a principal student clientele which may be more mindful of the importance of fair trade. The history of Würzburg is also noteworthy because more than 80% of the city was destroyed in a matter of minutes during the Second World War when the British Royal Air force firebombed this predominantly civilian city and killed an estimated 5,000 residents. Residents of the city may be therefore especially sensitive to songs and imagery that evoke the importance of peace and the perils of war.

Some of the next steps in exploring this fascinating link between background music and behavior is to replicate the findings in other cities and also with participants from varying age groups and cultural backgrounds. Another avenue of research could be to assess whether the content of the lyrics affects distinct forms of behavior. Are there some prosocial songs which would increase local prosocial behavior such as tipping or supporting local charities whereas others may increase global social awareness? How long do the effects of the music last? Are customers consciously aware of the lyrics they are hearing in the background or are they just reacting subconsciously? The number of questions raised by this study shows us how exciting the topic is and that we will likely see more field studies in the years to come that will enlighten us.


1.              Ruth, N. (2016). Heal the World”: A field experiment on the effects of music with prosocial lyrics on prosocial behavior. Psychology of Music, (in press).

2.              Jacob, C., Guéguen, N., & Boulbry, G. (2010). Effects of songs with prosocial lyrics on tipping behavior in a restaurant. International Journal of Hospitality Management, 29(4), 761-763.


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


Ruth, N. (2016). “Heal the World”: A field experiment on the effects of music with prosocial lyrics on prosocial behavior Psychology of Music DOI: 10.1177/0305735616652226

The Mesh of Civilizations in Cyberspace

“The great divisions among humankind and the dominating source of conflict will be cultural. Nation states will remain the most powerful actors in world affairs, but the principal conflicts of global politics will occur between nations and groups of different civilizations. The clash of civilizations will dominate global politics.”

—Samuel P. Huntington (1972-2008) “The Clash of Civilizations

In 1993, the Harvard political scientist Samuel Huntington published his now infamous paper The Clash of Civilizations in the journal Foreign Affairs. Huntington hypothesized that conflicts in the post-Cold War era would occur between civilizations or cultures and not between ideologies. He divided the world into eight key civilizations which reflected common cultural and religious heritages: Western, Confucian (also referred to as “Sinic”), Japanese, Islamic, Hindu, Slavic-Orthodox, Latin-American and African. In his subsequent book “The Clash of Civilizations and the Remaking of the World Order“, which presented a more detailed account of his ideas and how these divisions would fuel future conflicts, Huntington also included the Buddhist civilization as an additional entity. Huntington’s idea of grouping the world in civilizational blocs has been heavily criticized for being overly simplistic and ignoring the diversity that exists within each “civilization”. For example, the countries of Western Europe, the United States, Canada and Australia were all grouped together under “Western Civilization” whereas Turkey, Iran, Pakistan, Bangladesh and the Gulf states were all grouped as “Islamic Civilization” despite the fact that the member countries within these civilizations exhibited profound differences in terms of their cultures, languages, social structures and political systems. On the other hand, China’s emergence as a world power that will likely challenge the economic dominance of Western Europe and the United States, lends credence to a looming economic and political clash between the “Western” and “Confucian” civilizations. The Afghanistan war and the Iraq war between military coalitions from the “Western Civilization” and nations ascribed to the “Islamic Civilization” both occurred long after Huntington’s predictions were made and are used by some as examples of the hypothesized clash of civilizations.


It is difficult to assess the validity of Huntington’s ideas because they refer to abstract notions of cultural and civilizational identities of nations and societies without providing any clear evidence on the individual level. Do political and economic treaties between the governments of countries – such as the European Union – mean that individuals in these countries share a common cultural identity?

Also, the concept of civilizational blocs was developed before the dramatic increase in the usage of the internet and social media which now facilitate unprecedented opportunities for individuals belonging to distinct “civilizations” to interact with each other. One could therefore surmise that civilizational blocs might have become relics of the past in a new culture of global connectivity. A team of researchers from Stanford University, Cornell University and Yahoo recently decided to evaluate the “connectedness” of the hypothesized Huntington civilizations in cyberspace and published their results in the article “The Mesh of Civilizations in the Global Network of Digital Communication“.

The researchers examined Twitter users and the exchange of emails between Yahoo-Mail users in 90 countries with a minimum population of five million. In total, they analyzed “hundreds of millions of anonymized email and Twitter communications among tens of millions of worldwide users to map global patterns of transnational interpersonal communication”. Twitter data is public and freely available for researchers to analyze whereas emails had to be de-identified for the analysis. The researchers did not have any access to the content of the emails, they only analyzed whether users any given country were emailing users in other countries. The researchers focused on bi-directional ties. This means that ties between Twitter user A and B were only counted as a “bi-directional” tie or link if A followed B and B followed A on Twitter. Similarly, for the analysis of emails analysis, the researchers only considered email ties in which user X emailed user Y, and there was at least one email showing that user Y had also emailed user X. This requirement for bi-directionality was necessary to exclude spam tweets or emails in which one user may send out large numbers of messages to thousands of users without there being any true “tie” or “link” between the users that would suggest an active dialogue or communication.

Countries are clustered based on the difference between observed and expected density of social ties in 90 countries with population above 5 million, based on interpersonal email and Twitter communication.
Credit: State et al, PloS ONE 2015Countries are clustered based on the difference between observed and expected density of social ties in 90 countries with population above 5 million, based on interpersonal email and Twitter communication.

The researchers then created a cluster graph which is shown in the accompanying figure. Each circle represents a country and the 1000 strongest ties between countries are shown. The closer a circle is to another circle, the more email and Twitter links exist between individuals residing in the two countries. For the mathematical analysis to be unbiased, the researchers did not assign any countries to “civilizations” but they did observe key clusters of countries emerge which were very close to each other in the graph. They then colored in the circles with colors to reflect the civilization category as defined by Huntington and also colored ties within a civilization as the same color whereas ties between countries of two distinct civilization categories were kept in gray.

At first glance, these data may appear as a strong validation of the Huntington hypothesis because the circles of any given color (i.e. a Huntington civilization category) are overall far closer to each other on average that circles of a different color. For example, countries belonging to the “Latin American Civilization” (pink) countries strongly cluster together and some countries such as Chile (CL) and Peru (PE) have nearly exclusive intra-civilizational ties (pink). Some of the “Slavic-Orthodox Civilization” (brown) show strong intra-civilizational ties but Greece (GR), Bulgaria (BG) and Romania (RO) are much closer to Western European countries than other Slavic-Orthodox countries, likely because these three countries are part of the European Union and have shared a significant cultural heritage with what Huntington considers the “Western Civilization”. “Islamic Civilization” (green) countries also cluster together but they are far more spread out. Pakistan (PK) and Bangladesh (BD) are far closer to each other and to India (IN), which belongs to the “Hindu Civilization” (purple) than to Tunisia (TN) and Yemen (YE) which Huntington also assigned to an ‘Islamic Civilization”.

One obvious explanation for there being increased email and Twitter exchanges between individuals belonging to the same civilization is the presence of a shared language. The researchers therefore analyzed the data by correcting for language and found that even though language did contribute to Twitter and email ties, the clustering according to civilization was present even when taking language into account. Interestingly, of the various factors that could account for the connectedness between users, it appeared that religion (as defined by the World Religion Database) was one of the major factors, consistent with Huntington’s focus on religion as a defining characteristic of a civilization. The researchers conclude that “contrary to the borderless portrayal of cyberspace, online social interactions do not appear to have erased the fault lines Huntington proposed over a decade before the emergence of social media.”  But they disagree with Huntington in that closeness of countries belonging to a civilization does not necessarily imply that it will lead to conflicts or clashes with other civilizations.

It is important to not over-interpret one study on Twitter and Email links and make inferences about broader cultural or civilizational identities just because individuals in two countries follow each other on Twitter or write each other emails. The study did not investigate cultural identities of individuals and some of the emails could have been exchanged as part of online purchases without indicating any other personal ties. However, the data presented by the researchers does reveal some fascinating new insights about digital connectivity that are not discussed in much depth by the researchers. China (CN) and Great Britain (GB) emerge as some of the most highly connected countries at the center of the connectivity map with strong global ties, including India and countries in Africa. Whether this connectivity reflects the economic growth and increasing global relevance of China or a digital footprint of the British Empire even decades after its demise would be a worthy topic of investigation. The public availability of Twitter data makes it a perfect tool to analyze the content of Twitter communications and thus define how social media is used to engage in dialogue between individuals across cultural, religious and political boundaries by analyzing culturally relevant keywords used in tweets. Analyses of Twitter data over time could test the intriguing hypothesis whether connectivity and the content of communications between users living in different countries change over time. Such a study would be even more informative in terms of linking cyberspace connectivity to cultural identities and could provide insights into the evolution of digital ties over time.



Huntington, S. P. (1993). The Clash of Civilizations. Foreign Affairs, 72(3) 22-49.

State, B., Park, P., Weber, I., & Macy, M. (2015). The mesh of civilizations in the global network of digital communication. PLoS ONE, 10(5), e0122543.

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

State, B., Park, P., Weber, I., & Macy, M. (2015). The Mesh of Civilizations in the Global Network of Digital Communication PLOS ONE, 10 (5) DOI: 10.1371/journal.pone.0122543

Nostalgia is a Muse

“Let others praise ancient times. I am glad that I was born in these.”

                                                                                                – Ovid in “Ars Amatoria”

When I struggle with scientist’s block, I play 1980s music with the hope that the music will inspire me. This blast from the past often works for me. After listening to the songs, I can sometimes perceive patterns between our various pieces of cell biology and molecular biology data that had previously eluded me and design new biological experiments. But I have to admit that I have never performed the proper music control studies. Before attributing inspirational power to songs such as “99 Luftballons“, “Bruttosozialprodukt” or “Billie Jean“, I ought to spend equal time listening to music from other decades and then compare the impact of these listening sessions. I have always assumed that there is nothing intrinsically superior or inspirational about these songs, they simply evoke memories of my childhood. Eating comfort foods or seeing images of Munich and Lagos that remind me of my childhood also seem to work their muse magic.

Camera nostalgia

My personal interpretation has been that indulging nostalgia somehow liberates us from everyday issues and worries – some trivial, some more burdensome – which in turn allows us to approach our world with a fresh, creative perspective. It is difficult to make such general sweeping statements based on my own anecdotal experiences and I have always felt a bit of apprehension about discussing this with others. My nostalgia makes me feel like an old fogey who is stuck in an ossified past. Nostalgia does not have a good reputation. The German expression “Früher war alles besser!” (Back then, everything used to be better!) is used in contemporary culture to mock those who always speak of the romanticized past with whimsical fondness. In fact, the expression nostalgia was coined in 1688 by the Swiss medical student Johannes Hofer. In his dissertation “Dissertatio Medica de Nostalgia oder Heimweh“, Hofer used nostalgia as an equivalent of the German word Heimweh (“home-ache”), combining the Greek words nostos(homecoming) and algos (ache or pain), to describe a medical illness characterized by a “melancholy that originates from the desire to return to one’s homeland“. This view of nostalgia as an illness did not change much during the subsequent centuries where it was viewed as a neurological or psychiatric disorder.

This view has been challenged by the University of Southampton researchers Constantine Sedikides and Tim Wildschut, who have spent the past decade studying the benefits of nostalgia. Not only do they disavow its disease status, they have conducted numerous studies which suggest that nostalgia can make us more creative, open-minded and charitable. The definition of nostalgia used by Sedikides and Wildschut as a “sentimental longing for one’s past” is based on the contemporary usage by laypersons across many cultures. This time-based definition of nostalgia also represents a departure from its original geographical or cultural coinage by Hofer who viewed it as a longing for the homeland and not one’s personal past.

In one of their most recent experiments, Sedikides and Wildschut investigate nostalgia as a “mnemonic muse“. The researchers first evoked nostalgic memories in participants with the following prompt:

“Please think of a nostalgic event in your life. Specifically, try to think of a past event that makes you feel most nostalgic. Bring this nostalgic experience to mind. Immerse yourself in the nostalgic experience. How does it make you feel?”

Importantly, each experiment also involved a control group of participants who were given a very different prompt:

“Please bring to mind an ordinary event in your life. Specifically, try to think of a past event that is ordinary. Bring this ordinary experience to mind. Immerse yourself in the ordinary experience. How does it make you feel?”

This allowed the researchers to compare whether specifically activating nostalgia had a distinct effect from merely activating a general memory.

After these interventions, participants in the nostalgia group and in the control group were asked to write a short story involving a princess, a cat and a race car. In an additional experiment, participants finished a story starting with the sentence: “One cold winter evening, a man and a woman were alarmed by a sound coming from a nearby house“. After 30 minutes, of writing, the stories were collected and scored for the level of creativity by independent evaluators who had no knowledge of the experimental design or group that the participants belonged to. Participants who had experienced more nostalgia wrote more creative prose!

This is just one example of the dozens of studies conducted by Sedikides and Wildschut which show the benefits of nostalgia, such as providing inspiration, increasing trust towards outsiders and enhancing the willingness to donate to charities. What is the underlying mechanism for these benefits? Sedikides and Wildschut believe that our nostalgic memories provide a sense of belonging and support, which in turn helps our self-confidence and self-esteem. The comfort of our past gives us strength for our future.

Does this mean that this longing for the past is always a good thing? Not every form of nostalgia centers on personal childhood memories. For example, there is a form of ideological nostalgia expressed by groups who feel disenfranchised by the recent progress and long for days of former power and privilege. The South African sociologists van der Waal and Robbins recently described the popularity of a song about the Anglo-Boer waramong white Afrikaans-speakers in the post-Apartheid era which may have been rooted in a nostalgic affirmation of white Afrikaner identity. It is conceivable that similar forms of ideological nostalgia could be found in other cultures and states where privileged classes and races are losing ground to increased empowerment of the general population.

It is important that we distinguish between these two forms of nostalgia – personal childhood nostalgia and ideological group nostalgia – before “rehabilitating” nostalgia’s reputation. The research by Sedikides and Wildschut clearly demonstrates that nostalgia can be a powerful tool to inspire us but we have to ensure that it is not misused as am ideological or political tool to manipulate us.


1. de Diego, F. F., & Ots, C. V. (2014). Nostalgia: a conceptual history. History of psychiatry, 25(4), 404-411.

2. Sedikides, C., & Wildschut, T. (2016). Past Forward: Nostalgia as a Motivational Force. Trends in cognitive sciences (published online Feb 18, 2016)

3. van Tilburg, W. A., Sedikides, C., & Wildschut, T. (2015). The mnemonic muse: Nostalgia fosters creativity through openness to experience.Journal of Experimental Social Psychology, 59, 1-7.

4. Van der Waal, K., & Robins, S. (2011). ‘De la Rey’and the Revival of ‘Boer Heritage’: Nostalgia in the Post-apartheid Afrikaner Culture Industry. Journal of Southern African Studies, 37(4), 763-779.


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

van Tilburg, W., Sedikides, C., & Wildschut, T. (2015). The mnemonic muse: Nostalgia fosters creativity through openness to experience Journal of Experimental Social Psychology, 59, 1-7 DOI: 10.1016/j.jesp.2015.02.002

Shame on You, Shame on Me: Shame as an Evolutionary Adaptation

Can shame be good for you? We often think of shame as a shackling emotion which thwarts our individuality and creativity. A sense of shame could prevent us from choosing a partner we truly love, speaking out against societal traditions which propagate injustice or pursuing a profession that is deemed unworthy by our peers. But if shame is so detrimental, why did we evolve with this emotion? A team of researchers led by Daniel Sznycer from the Center for Evolutionary Psychology at the University of California, Santa Barbara recently published a study in the Proceedings of the National Academy of Sciences which suggests that shame is an important evolutionary adaptation. According to their research which was conducted in the United States, Israel and India, the sense of shame helps humans avoid engaging in acts that could lead to them being devalued and ostracized by their community.

L0035595 An Iron 'scolds bridle' mask used to publicaly humiliate
A Belgian Iron ‘scolds bridle’ or ‘branks’ mask, with bell, used to publicly humiliate and punish, mainly women, for speaking out against authority, nagging, brawling with neighbors, blaspheming or lying via Wellcome Images

For their first experiment, the researchers enrolled participants in the USA (118 participants completed the study; mean age of 36; 53% were female) and India (155 participants completed the study, mean age of 31, 38% were female) using the online Amazon Mechanical Turk crowdsourcing platform as well as 165 participants from a university in Israel (mean age of 23; 81% female). The participants were randomly assigned to two groups and presented with 29 scenarios: The “shame group” participants were asked to rate how much shame they would experience if they lived through any given scenario and whereas the “audience group” participants were asked how negatively they would rate a third-party person of the same age and gender as the participants in an analogous scenario.

Here is a specific scenario to illustrate the study design:

Male participants in the “shame group” were asked to rate “At the wedding of an acquaintance, you are discovered cheating on your wife with a food server” on a scale ranging from 1 (no shame at all) to 7 (a lot of shame).

Female participants in the “shame group” were asked to rate “At the wedding of an acquaintance, you are discovered cheating on your husband with a food server” on a scale ranging from 1 (no shame at all) to 7 (a lot of shame).

Male participants in the “audience group”, on the other hand, were asked to rate “At the wedding of an acquaintance, he is discovered cheating on his wife with a food server” on a scale ranging from 1 (I wouldn’t view him negatively at all) to 7 (I’d view him very negatively).

Female participants in the “audience group” rated “At the wedding of an acquaintance, she is discovered cheating on her husband with a food server” on a scale ranging from 1 (I wouldn’t view her negatively at all) to 7 (I’d view her very negatively).

To give you a sense of the breadth of scenarios that the researchers used, here are some more examples:

You stole goods from a shop owned by your neighbor.

You cannot support your children economically.

You get into a fight in front of everybody and your opponent completely dominates you with punch after punch until you’re knocked out.

You receive welfare money from the government because you cannot financially support your family.

You are not generous with others.

For each of the 29 scenarios, the researchers created gender-specific “shame” and “audience” versions. The “audience group” reveals how we rate the bad behavior of others (devaluation) whereas the “shame group” provides information into how much shame we feel if we engage in that same behavior. By ensuring that participants only participated in one of the two groups, the researchers were able to get two independent scores – shame versus devaluation – for each scenario.

The key finding of this experiment was that the third-party devaluation scores were highly correlated with the shame scores in all three countries. For example, here are the mean “shame scores” for the wedding infidelity scenario indicating that people in all three countries would have experienced a lot of shame:

USA: 6.5

India: 5.7

Israel: 6.7

The devaluation scores from the third-party “audience group” suggested that people viewed the behavior very negatively:

USA: 6.4

India: 5.1

Israel: 6.6

For nearly all the scenarios, the researchers found a surprisingly strong correlation between devaluation and shame and they also found that the correlation was similarly strong in each of the surveyed countries.

The researchers then asked the question whether this correlation between personal shame and third-party negative valuation was unique to the shame emotion or whether other negative emotions such as anxiety or sadness would also correlate equally well with devaluation. This experiment was only conducted with the participants in the USA and India. The researchers found that even though the fictitious scenarios elicited some degree of anxiety and sadness in the participants, the levels of anxiety or sadness were not significantly correlated with the extent of devaluation. The researchers interpreted these results as suggesting that there is something special about shame because it tracks so closely with how bad behavior is perceived by others whereas sadness or anxiety do not.

How do these findings inform our view on the evolutionary role of shame? The researchers suggest that instead of designating shame as an “ugly” emotion, it is instead an excellent predictor of how our peers would view our behaviors and thus deter us from making bad choices that could undermine our relationships with members of our community. The strong statistical correlations between shame and negative valuation of the behaviors as well as the universality of this link in the three countries indeed support the conclusions of the researchers. However, there are also so important limitations of these studies. As with many evolutionary psychology studies, it is not easy to ascribe a direct cause-effect relationship based on a correlation. Does devaluation lead to evolving a shame mechanism or is it perhaps the other way around? Does a sense of shame lead to a societal devaluation of certain behaviors such as dishonesty? It is also possible that the participants in the audience group responded with the concept of “shame” in the back of their mind even though they were not asked to directly comment on how shameful the act was. Perhaps their third-party assessments of how bad the behavior was were clouded by their own perceptions of how shameful the behavior would be if they themselves had engaged in it.

Another limitation of the study is that the participants represented a young subgroup of society. The mean ages of 23 (Israel), 31 (India) and 36 (USA) as well as the use of an online Amazon Mechanical Turk questionnaire means that the study results predominantly reflect the views of Millennials. The similarities of the shame and devaluation scores in three distinct cultures are among the most remarkable findings of these studies. However, perhaps they are more reflective of a global convergence of values among the Millennial generation than an underlying evolutionary conservation of an adaptive mechanism.

These limitations should not detract from the provocative questions raised by the studies. They force us to rethink how we view shame. Like all adaptive defense mechanisms, shame could go awry. Our immune function, for example, is an essential defense mechanism but an unfettered immune response can destroy the very body it is trying to protect. Perhaps shame acts in a similar fashion. A certain level of shame could help us function in society by promoting certain moral values such as justice, honesty or generosity. But an excess of shame may become a maladaptive prison which compromises our individuality.


Daniel Sznycer, John Tooby, Leda Cosmides, Roni Porat, Shaul Shalvi, and Eran Halperin. (2016). “Shame closely tracks the threat of devaluation by others, even across culturesProceedings of the National Academy of Sciences

Sznycer D, Tooby J, Cosmides L, Porat R, Shalvi S, & Halperin E (2016). Shame closely tracks the threat of devaluation by others, even across cultures. Proceedings of the National Academy of Sciences of the United States of America PMID: 26903649

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