Survey on Sleeping – Longest Time Awake

Here I presented some basic results of my survey on sleeping. The analysis showed that the male respondents reported having been awake a maximum of 40.6 h, while for women this was 36.6 h, not an enormous difference, but statistically significant at p < 0.05. I also wanted to give you the breakdown for all of the respondents, male or female:


You can see that around 25 % (1 in 4) never made it past the 24 h mark. Roughly the same percentage (adding up the final four bars) made it past the 48 h mark and a brave 4.4 % (1 in 23) even past the 72 h mark. Feel free to use the comments section to tell me what the longest time you were awake was and what the circumstances were that made you stay up so long.

Survey on Sleeping

I conducted a paid survey via AYTM on the topic of sleeping. I was interested in finding out what variables (psychological, lifestyle, circumstance) have a noticeable effect on sleep related issues such as nightmares, sleep duration, time needed to fall asleep, etc … Now that I’ve got the raw data result, there’s a ton of relationships to analyze and that will take time. But I’ve already found a few neat statistically significant results, some to be expected, some rather surprising. I’ll publish them, as well as the results yet to be found, here on my blog in the coming weeks.

Geographic Region: US

Number of Respondents: 250

Males: 96 (38.4 %)
Females: 154 (61.6 %)

Minimum Age: 18
Median Age: 36
Maximum Age: 81

White-American: 163 (65.2 %)
African-American: 23 (9.2 %)
Asian-American: 17 (6.8 %)
Hispanic-American: 28 (11.2 %)
Other: 19 (7.6 %)

Here’s what I extracted from the data so far. Statistical significance was determined via a two-population Z-test. Notice the p-value. You can interpret it as the chance that the result came to be by random fluctuations rather than via a real effect. Hence, the lower the p-value, the more significant and reliable the result. A p-value of 0.05 roughly means that there’s a 1 in 20 chance that the result is just a random fluctuation, a value of 0.01 that there’s a 1 in 100 chance for the same. All of the results below are significant at p < 0.05, some even at p < 0.01.

By the way: if you’ve got your own data, you can let this great website do a two-population Z-test for you. Only works though if you’ve got the result in form of a percentage. To learn more about hypothesis testing, including how to perform a Z-test if the data is not given in form of a percentage, check out this great book by Leonard Gaston.


Hypothesis: Young people have more nightmares

Percentage of people with nightmares for people at median age or younger: 49.6 %
Number of respondents: 127

Percentage of people with nightmares for people older than median age: 26.8 %
Number of respondents: 123

The Z-Score is 3.706. The p-value is 0.0001. The result is significant at p < 0.01.

Correlation between age and probability for nightmares: Probability = 0.757 – 0.00958·Age
(Every year the chance for nightmares goes down by roughly 1 %)

Hypothesis: Young people are more light sensitive

Percentage of light sensitive people for people at median age or younger: 62.2 %
Number of respondents: 127

Percentage of light sensitive people for people older than median age: 49.6 %
Number of respondents: 123

The Z-Score is 2.0065. The p-value is 0.02222. The result is significant at p < 0.05.

Correlation between age and probability for light sensitivity: Probability = 0.756 – 0.00504·Age
(Every two years the chance for light sensitivity goes down by 1 %)

Hypothesis: Older people more frequently take naps

Percentage of people taking naps for people at median age or younger: 23.6 %
Number of respondents: 127

Percentage of people taking naps for people older than median age: 33.3 %
Number of respondents: 123

The Z-Score is 1.7009. The p-value is 0.04457. The result is significant at p < 0.05.

Correlation between age and probability for taking naps: Probability = 0.194 + 0.00232·Age
(Every four years the chance for taking naps goes up by 1 %)


Hypothesis: Females wake up more frequently at night

Percentage of males who frequently wake up at night: 51.1 %
N = 96

Percentage of females who frequently wake up at night: 64.3 %
N = 154

The Z-Score is 2.081. The p-value is 0.03752. The result is significant at p < 0.05.

Hypothesis: Males have a higher peak waking duration

Peak waking duration for males: 40.6 h
SEM: 1.76 h

Peak waking duration for females: 36.6 h
SEM: 1.33 h

The Z-Score is 1.8132. The p-value is 0.0349. The result is significant at p < 0.05.


Hypothesis: People with low income daydream more

Percentage of people with low income who frequently daydream: 40.1 %
N = 142

Percentage of people with high income who frequently daydream: 26.9 %
N = 108

The Z-Score is 2.1764. The p-value is 0.01463. The result is significant at p < 0.05.

Hypothesis: People with low income take longer to fall asleep

Time to fall asleep for people with low income: 31.4 min
SEM = 1.44 min

Time to fall asleep for people with high income: 22.9 min
SEM = 1.08 min

The Z-Score is 4.7222. The p-value is < 0.00001. The result is significant at p < 0.01.


Hypothesis: Depressed people have more nightmares

Percentage of people with nightmares for depressed people: 57.1 %
Number of respondents: 84

Percentage of people with nightmares for non-depressed people: 28.9 %
Number of respondents: 166

The Z-Score is 4.3308. The p-value is 0. The result is significant at p < 0.01.

Hypothesis: Depressed people daydream more

Percentage of depressed people who frequently daydream: 50.3 %
N = 84

Percentage of non-depressed people who frequently daydream: 26.5 %
N = 166

The Z-Score is 3.7392. The p-value is 9E-05. The result is significant at p < 0.01.

Hypothesis: Depressed people need more time to feel fully awake after a good night’s sleep

Time to feel fully awake for depressed people: 42.5 min
SEM: 2.70 min

Time to feel fully awake for non-depressed people: 28.9 min
SEM: 1.27 min

The Z-Score is 4.5580. The p-value is < 0.00001. The result is significant at p < 0.01.


Hypothesis: People who need more time to fall asleep also need more time to feel fully awake after a good night’s sleep

Time to feel fully awake for people who need less than 30 minutes to fall asleep: 29.9 min
SEM: 1.77 min

Time to feel fully awake for people who need 30 minutes or more to fall asleep: 37.1 min
SEM: 1.92 min

The Z-Score is 2.7572. The p-value is 0.002915. The result is significant at p < 0.01.

Correlation between time falling asleep (FAS) versus time to feel fully awake (FAW):

FAW = 24.7 + 0.317*FAS

(Every ten minutes additional time needed to fall asleep translate into roughly three minutes additional time required to feel fully awake after a good night’s sleep)

The Placebo Effect – An Overview

There is a major problem with reliance on placebos, like most vitamins and antioxidants. Everyone gets upset about Big Science, Big Pharma, but they love Big Placebo.

– Michael Specter

A Little White Lie

In 1972, Blackwell invited fifty-seven pharmacology students to an hour-long lecture that, unbeknownst to the students, had only one real purpose: bore them. Before the tedious lecture began, the participants were offered a pink or a blue pill and told that the one is a stimulant and the other a sedative (though it was not revealed which color corresponded to which effect – the students had to take their chances). When measuring the alertness of the students later on, the researchers found that 1) the pink pills helped students to stay concentrated and 2) two pills worked better than one. The weird thing about these results: both the pink and blue pills were plain ol’ sugar pills containing no active ingredient whatsoever. From a purely pharmacological point of view, neither pill should have a stimulating or sedative effect. The students were deceived … and yet, those who took the pink pill did a much better job in staying concentrated than those who took the blue pill, outperformed only by those brave individuals who took two of the pink miracle pills. Both the effects of color and number have been reproduced. For example, Luchelli (1972) found that patients with sleeping problems fell asleep faster after taking a blue capsule than after taking an orange one. And red placebos have proven to be more effective pain killers than white, blue or green placebos (Huskisson 1974). As for number, a comprehensive meta-analysis of placebo-controlled trials by Moerman (2002) confirmed that four sugar pills are more beneficial than two. With this we are ready to enter another curious realm of the mind: the placebo effect, where zero is something and two times zero is two times something.

The Oxford Dictionary defines the placebo effect as a beneficial effect produced by a placebo drug or treatment, which cannot be attributed to the properties of the placebo itself and must therefore be due to the patient’s belief in that treatment. In short: mind over matter. The word placebo originates from the Bible (Psalm 116:9, Vulgate version by Jerome) and translates to “I shall please”, which seems to be quite fitting. Until the dawn of modern science, almost all of medicine was, knowingly or unknowingly, based on this effect. Healing spells, astrological rituals, bloodletting … We now know that any improvement in health resulting from such crude treatments can only arise from the fact that the patient’s mind has been sufficiently pleased. Medicine has no doubt come a long way and all of us profit greatly from this. We don’t have to worry about dubious healers drilling holes into our brains to “relieve pressure” (an extremely painful and usually highly ineffective treatment called trepanning), we don’t have to endure the unimaginable pain of a surgeon cutting us open and we live forty years longer than our ancestors. Science has made it possible. However, even in today’s technology-driven world one shouldn’t underestimate the healing powers of the mind.

Before taking a closer look at relevant studies and proposed explanations, we should point out that studying the placebo effect can be a rather tricky affair. It’s not as simple as giving a sugar pill to an ill person and celebrating the resulting improvement in health. All conditions have a certain natural history. Your common cold will build up over several days, peak over the following days and then slowly disappear. Hence, handing a patient a placebo pill (or any other drug for that matter) when the symptoms are at their peak and observing the resulting improvement does not allow you to conclude anything meaningful. In this set-up, separating the effects of the placebo from the natural history of the illness is impossible. To do it right, researchers need one placebo group and one natural history (no-treatment) group. The placebo response is the difference that arises between the two groups. Ignoring natural history is a popular way of “proving” the effectiveness of sham healing rituals and supposed miracle pills. You can literally make any treatment look like a gift from God by knowing the natural history and waiting for the right moment to start the treatment. One can already picture the pamphlet: “93 % of patients were free of symptoms after just three days, so don’t miss out on this revolutionary treatment”. Sounds great, but what they conveniently forget to mention is that the same would have been true had the patients received no treatment.

There are also ethical consideration that need to be taken into account. Suppose you wanted to test how your placebo treatment compares to a drug that is known to be beneficial to a patient’s health. The scientific approach demands setting up one placebo group and one group that receives the well-known drug. How well your placebo treatment performs will be determined by comparing the groups after a predetermined time has passed. However, having one placebo group means that you are depriving people of a treatment that is proven to improve their condition. It goes without saying that this is highly problematic from an ethical point of view. Letting the patient suffer for the quest of knowledge? This approach might be justified if there is sufficient cause to believe that the alternative treatment in question is superior, but this is rarely the case for placebo treatments. While beneficial, their effect is usually much weaker than that of established drugs.

Another source of criticism is the deception of the patient during a placebo treatment. Doctors prefer to be open and honest when discussing a patient’s conditions and the methods of treatment. But a placebo therapy requires them to tell patients that the prescribed pill contains an active ingredient and has proven to be highly effective when in reality it’s nothing but sugar wrapped in a thick layer of good-will. Considering the benefits, we can certainly call it a white lie, but telling it still makes many professionals feel uncomfortable. However, they might be in luck. Several studies have suggested that, surprisingly, the placebo effect still works when the patient is fully aware that he receives placebo pills.

Experimental Evidence

One example of this is the study by Kaptchuk et al. (2010). The Harvard scientists randomly assigned 80 patients suffering from irritable bowel syndrome (IBS) to either a placebo group or no-treatment group. The patients in the placebo group received a placebo pill along with the following explanation: “Placebo pills are made of an inert substance, like sugar pills, and have been shown in clinical studies to produce significant improvement in IBS symptoms through mind-body self-healing processes”. As can be seen from the graph below, the pills did their magic. The improvement in the placebo group was roughly 30 % higher than in the no-treatment group and the low p-value (see appendix for an explanation of the p-value) shows that it is extremely unlikely that this result came to be by chance. Unfortunately, there seems to be a downside to the honesty. Hashish (1988) analyzed the effects of real and sham ultrasound treatment on patients whose impacted lower third molars had been surgically removed and concluded that the effectiveness in producing a placebo response is diminished if the patient comes to understand that the therapy is a placebo treatment rather than the “real” one. So while the placebo-effect does arise even without the element of deception, a fact that is quite astonishing on its own, deception does strengthen the response to the placebo treatment.


Results of Kaptchuk et al. (2010)

Let’s explore some more experimental studies to fully understand the depth and variety of the placebo effect. A large proportion of the relevant research has focused on the effect’s analgesic nature, that is, its ability to reduce pain without impairing consciousness. Amanzio et al. (2001) examined patients who had undergone thoracotomy, a major surgical procedure to gain access to vital organs in the chest and one that is often associated with severe post-operative pain. As handing out sugar pills would have been irresponsible and unethical in this case, the researchers found a more humane method of unearthing the placebo effect: the open-hidden paradigm. All patients received powerful painkillers such as Morphine, Buprenorphine, Tramadol, … However, while one group received the drug in an open manner, administered by a caring clinician in full view of the patient, another group was given the drug in a hidden manner, by means of a computer-programmed drug infusion pump with no clinician present and no indication that the drug was being administered. This set-up enabled the researchers to determine how much of the pain reduction was due to the caring nature of the clinician and the ritual of injecting the drug. The results: the human touch matters and matters a lot. As can be seen from the graph below, every painkiller became significantly more effective when administered in an open fashion. Several follow-on studies (Benedetti et al. 2003, Colloca et al. 2004) confirmed this finding. This demonstrates that the placebo effect goes far beyond the notorious sugar pill, it can also be induced by the caring words of a professional or a dramatic treatment ritual.

Results of Amanzio et al. (2001)

The fact that the human touch is of major importance in any clinical treatment, placebo or otherwise, seems pretty obvious (though its power in reducing pain might have surprised you). Much less obvious are the roles of administration form and treatment ritual, something we shall further explore. For both we can use the following rule of thumb: the more dramatic the intervention, the stronger the placebo response. For example, several studies have shown that an injection with salt-water is more effective in generating the placebo effect than a sugar pill. This is of course despite the fact that both salt-water and sugar pills do not have any direct medical benefits. The key difference lies in the inconveniences associated with the form of delivery: while swallowing a pill takes only a moment and is a rather uncomplicated process, the injection, preparation included, might take up to several minutes and can be quite painful. There’s no doubt that the latter intervention will leave a much stronger impression. Another study (Kaptchuk et al. 2006) came to the exciting conclusion that a nonsensical therapeutic intervention modeled on acupuncture did a significantly better job in reducing arm pain than the sugar pill. While the average pain score in the sham acupuncture group dropped by 0.33 over the course of one week, the corresponding drop in the sugar pill group was only 0.15. Again the more dramatic treatment came out on top.

The experimental results mentioned above might explain why popular ritualistic treatments found in alternative medicine remain so widespread even when there are numerous studies providing ample proof that the interventions lack biological plausibility and produce no direct medical benefits. Despite their scientific shortcomings, such treatments do work. However, this feat is extremely unlikely to be accomplished by strengthening a person’s aura, enhancing life force or harnessing quantum energy, as the brochure might claim. They work mainly (even solely) because of their efficiency in inducing the mind’s own placebo effect. Kaptchuk’s study impressively demonstrates that you can take any arbitrary ritual, back it up with any arbitrary theory to give the procedure pseudo-plausibility and let the placebo effect take over from there. Such a treatment might not be able to compete with cutting-edge drugs, but the benefits will be there. Though one has to wonder about the ethics of providing a patient with a certain treatment when demonstrably a more effective one is available, especially in case of serious diseases.

Don’t Forget Your Lucky Charm

This seems to be a great moment to get in the following entertaining gem. In 2010, Damish et al. invited twenty-eight people to the University of Cologne to take part in a short but sweet experiment that had them play ten balls on a putting green. Half of the participants were given a regular golf ball and managed to get 4.7 putts out of 10 on average. The other half was told they would be playing a “lucky ball” and, sure enough, this increased performance by an astonishing 36 % to 6.4 putts out of 10. I think we can agree that the researchers hadn’t really gotten hold of some magical performance-enhancing “lucky ball” and that the participants most likely didn’t even believe the story of the blessed ball. Yet, the increase was there and the result statistically significant despite the small sample size. So what happened? As you might have expected, this is just another example of the placebo effect (in this particular case also called the lucky charm effect) in action.

OK, so the ball was not really lucky, but it seems that simply floating the far-fetched idea of a lucky ball was enough to put participants into a different mindset, causing them to approach the task at hand in a different manner. One can assume that the story made them less worried about failing and more focused on the game, in which case the marked increase is no surprise at all. Hence, bringing a lucky charm to an exam might not be so superstitious after all. Though we should mention that a lucky charm can only do its magic if the task to be completed requires some skill. If the outcome is completely random, there simply is nothing to gain from being put into a different mindset. So while a lucky charm might be able to help a golfer, student, chess player or even a race car driver, it is completely useless for dice games, betting or winning the lottery.

Let’s look at a few more studies that show just how curious and complex the placebo effect is before moving on to explanations. Shiv et al. (2008) from the Stanford Business School analyzed the economic side of self-healing. They applied electric shocks to 82 participants and then offered them to buy a painkiller (guess that’s also a way to fund your research). The option: get the cheap painkiller for $ 0.10 per pill or the expensive one for $ 2.50 per pill. What the participants weren’t told was that there was no difference between the pills except for the price. Despite that, the price did have an effect on pain reduction. While 61 % of the subjects taking the cheap painkiller reported a significant pain reduction, an impressive 85 % reported the same after treating themselves to the expensive version. The researchers suspect that this is a result of quality expectations. We associate high price with good quality and in case of painkillers good quality equals effective pain reduction. So buying the expensive brand name drug might not be such a bad idea even when there is a chemically identical and lower priced generic drug available. In another study, Shiv et al. also found the same effect for energy drinks. The more expensive energy drink, with price being the only difference, made people report higher alertness and noticeably enhanced their ability to solve word puzzles.


This was an excerpt from my Kindle e-book Curiosities of the Mind. To learn more about the placebo effect, as well as other interesting psychological effects such as the chameleon effect, Mozart effect and the actor-observer bias, click here. (Link to

The Mozart Effect – Hype and Reality

The idea that music can make you smarter became very popular in the mid-nineties under the name “Mozart effect” and has remained popular ever since. The hype began with the publication of Rauscher et al. (1993) in the journal Nature. The researchers discovered that participants who were exposed to the aforementioned Mozart sonata performed better on the Stanford-Binet IQ test than those who listened to verbal relaxation instructions or sat in silence.

This revelation caused armies of mothers and fathers to storm the CD stores and bombard their children with Mozart music. One US governor ordered the distribution of Mozart CD’s by hospitals to all mothers following the birth of a child. Not surprisingly, marketers eagerly joined the fun (with increasingly ridiculous claims about the effect of music on intelligence) to profit from the newly-found “get-smart-quick” scheme. What got lost in the hype however was the fact that Rauscher et al. never found or claimed that exposure to Mozart would increase your IQ in general. Neither did they claim that the performance on an IQ test is a reliable indicator of how smart a person is. All they demonstrated was that exposure to an enjoyable musical piece led to a temporary (< 15 minutes) increase in spatial reasoning ability, not more, not less. Despite that, the study suffered the fate all studies are bound to suffer when they fall into the hands of the tabloid media, politicians and marketers: the results get distorted and blown out of proportion.

By the way: I wonder if mothers and fathers would have been just as eager to expose their children to Mozart had they known about some of the less flattering pieces written by the brilliant composer, among them the canon in B-flat major titled “Leck mich im Arsch” (which translates to “Kiss my Ass”) and the scatological canon “Bona Nox!” which includes the rather unsophisticated line “shit in your bed and make it burst”. These are just two examples of the many obscene and sometimes even pornographic pieces the party animal Mozart wrote for boozy nights with his friends. One can picture the young composer and his companions sitting in a flat in Vienna singing obscene songs after downing a few bottles of wine while concerned mothers cover their children’s ears, cursing the young generation and their vile music. That’s the side of Mozart you won’t get to hear in orchestral concerts.

But back to the topic. So whatever happened to the Mozart effect? Hype aside, is there anything to it? The thorough 1999 meta-analysis of Mozart effect studies by Chabris came to the conclusion that the popularized version of the effect is most certainly incorrect. Listening to Mozart, while no doubt a very enjoyable and stimulating experience, does not permanently raise your IQ or make you more intelligent. However, said meta analysis, as well as the 2002 Husain et al. study described above, did find a small cognitive enhancement resulting from exposure to Mozart’s sonata. The explanation of the enhancement turned out to be somewhat sobering though.

In the original study, Rauscher et al. proposed that Mozart’s music is able to prime spatial abilities in a direct manner because of similarities in neural activation. Further discussion and experiments showed that such a direct link is rather unlikely though, especially in light of the results of Nantais and Schellenberg (1999). In this study participants performed a spatial reasoning task after either listening to Mozart’s sonata or hearing a narrated story. When the reasoning task was completed, the participants were asked which of the two, Mozart’s piece or the story, they preferred. The result: participants who preferred the sonata performed better on the spatial reasoning task after listening to the piece and participants who preferred the story performed better on the test after hearing the story. However, participants who listened to Mozart’s music and stated that they would have preferred the story instead did not show the cognitive improvement. Overall the researchers found no benefit in the Mozart condition. All of the above implies that the enhancement in performance is a result of exposure to a preferred stimulus rather than a direct link between Mozart and cognition. It seems that the Mozart effect is just a small part of a broader psychological phenomenon that goes a little something like this: experiencing a preferred stimulus, be it a musical piece, a narrated story or a funny comic book, has a positive effect on arousal and mood and this in turn enhances cognitive abilities.

This was an extract from my Kindle e-book Curiosities of the Mind. Check it out if you interested in learning more about the psychological effects of music as well as other common psychological effects such as the false consensus bias, the placebo effect, the chameleon effect, …

New Kindle release: Curiosities of the Mind (Psychology)

After about six months of work and fun, my new Kindle book is finally ready and … surprise, it’s not math! This time we’ll be delving deep into the ultimate scientific challenge: the mind. Here’s the blurb and the Table of Contents:


Over the past centuries, science has successfully unlocked many secrets of the universe. We understand atoms and molecules, cells and organs, stars and galaxies and have managed to use this newly-found knowledge to build fantastic machines that can bring us from A to B at mind-blowing speeds and cutting-edge medication that can alleviate pain almost instantly. Yet, the grandest secret the universe has to offer remains a perplexing mystery: the mind.

Despite the incredible scientific progress, we still find ourselves wondering what it is, where it is and how it works. This book cannot hope to give you a full answer, but it will provide you with fascinating hints on the workings of this mysterious machine by discussing the strange curiosities manifested in it. You will get to know the most common psychological effects and biases, learn about illuminating experiments from the field of social psychology and find out a lot about yourself and the people around you in the process. For a detailed table of contents, check out the Look Inside feature.

Table of Contents:

– Placebo Effect
A Little White Lie
Experimental Evidence
Don’t Forget Your Lucky Charm
Poor Little Albert

– Chameleon Effect
Just A Harmless Fly
Now 10 % More Likable
It’s All About Empathy

– Childhood Amnesia
A Fundamental Part Of Being Human
The Nature Of Early Memories
Parents, Culture And Gender
The Self And Autobiographical Memories

– IKEA Effect
Labor Leads To Love
Cognitive Dissonances
High Expectations versus Low Rewards
Self-Perception Theory
Of Origami Frogs and Men

– False Consensus Effect
Bungee Jumping Enthusiasts Are Biased
What Would You Do?
A Powerful Defense Mechanism
Friends – A Biased Sample Of Mankind

– Actor – Observer Bias
Everybody’s To Blame Except You
Fidel Castro’s Army Of Students
A Matter Of Culture And Vision
Let’s Talk Later

– Dunning-Kruger Effect
Unskilled And Unaware
Learn To Be Better
Statistical Artifacts And Task Difficulty

– Music and the Mozart Effect
Tones and Overtones
Music And Your Mind
Say No to Marketers

– Appendix
Mean and Standard Deviation
Regression to the Mean

Click here to get to the product page on Amazon.