Category: Sleep and dreaming

It’s not just lack of sleep: why pupils with an “owl” chronotype get lower grades

Pupils with an “owl” chronotype may be at particular disadvantage for science and maths

By guest blogger Helge Hasselmann

Cognitive performance fluctuates throughout the day. Depending on their “chronotype” some people are sharpest in the morning (“larks”), while others generally prefer the later hours of the day (“owls”). For obvious reasons, this is mirrored in our preferred sleep routines: larks get tired in the evenings earlier and, as a consequence, also wake up earlier, while owls show the opposite pattern. Your chronotype is not something that you’re stuck with for the rest of your life, but it changes with age. In fact we’re most likely to show an owl-like chronotype during adolescence, which might at least partly explain why teenagers often stay up late and arrive at school with eyes bloodshot thanks to a hefty sleep debt.

But if late chronotypes are so common in adolescents, why does school start so early (usually well before 9am in the UK, Netherlands and Germany)? Doesn’t that mean that many students are likely to be constantly sleep-deprived and not assessed during their biological peaks? Yes, it does! In fact, there is a lot of evidence to suggest that school kids who have a late chronotype score lower grades. But besides reduced sleep time, there are several alternative explanations for why a late chronotype could be associated with lower academic performance (such as absenteeism, for instance) as explored in a new paper in Scientific Reports. The researchers, led by Giulia Zerbini at University of Groningen, say their findings might help us understand the chronotype/school grade link and how we can fix it.

Continue reading “It’s not just lack of sleep: why pupils with an “owl” chronotype get lower grades”

For faster learning and longer retention, interleave study sessions with sleep

Teenage schoolgirl sleeping on deskBy Christian Jarrett

Some basic rules of effective learning, informed by psychology, are already well established. Testing yourself and relearning any forgotten items is beneficial,  especially so when this is done after a sufficient delay, rather than “cramming”. Sleep too is known to be incredibly helpful for consolidating new memories. Now a study  in Psychological Science has built upon these insights, showing how interleaving two study periods with sleep leads to particularly efficient and long-lasting learning.  Continue reading “For faster learning and longer retention, interleave study sessions with sleep”

Studying “fast chess” to see how decision making varies through the day

38477719_ce9d3dc8a3_bBy Christian Jarrett

We’ve all had the experience of trying to make a tricky decision through the fog of fatigue, but there’s surprisingly little objective evidence about how time of day affects the way we decide. Perhaps late-day tiredness makes us more rash, as we lack the energy to be considered. Alternatively, maybe it’s our mid-morning zest that could lead us to be impetuous. Of course, our own chronotype is also likely come into play – perhaps morning people – “larks” – make better decisions in the morning, whereas evening people – “owls” – make better decisions in the evening.

One place to look for answers is in the data trails left by our online behavior. For a new paper in Cognition, a team led by María Leone has analysed the moves made by dozens of internet “fast chess” players, some of whom have played tens of thousands of two or three-minute games, consisting of an even greater number of moves. The results suggest that regardless of chronotype, we’re inclined to make progressively faster, less accurate decisions as the day wears on, with the effect plateauing in mid-afternoon.  Continue reading “Studying “fast chess” to see how decision making varies through the day”

When you’re sleeping, how much does your brain pay attention to the outside world?

Brain Sleep

By guest blogger Daniel Bor

When I was 13, I once dreamt that a beautiful woman was sensuously stroking the palm of my hand, as a family of fridges hummed in the background. In reality, a huge, buzzing wasp had landed on my right hand. It idly walked around for a bit, then stung me. After the shock had worn off, I was puzzled why my dreaming brain had stopped me from waking up to this potential danger. Contrast this with 6 years ago, when even my deepest sleep would be broken by the first sounds of my newborn baby daughter’s cries. How do our brains decide whether or not to wake us up, based on what’s going on in the world? And why does this policy change depending on whether we’re dreaming or in some other sleep state?

In a recent paper in the Journal of Neuroscience, Thomas Andrillon and his colleagues have discovered intriguing clues that start to answer these questions. Continue reading “When you’re sleeping, how much does your brain pay attention to the outside world?”

Puncturing the myth of the tireless leader – if you’re sleep deprived you’re unlikely to inspire anyone

Sleep deprivation makes it harder for us to inspire others, or to be inspired

There’s an archetype of the tireless leader who scorns slumber in favour of getting things done – Margaret Thatcher, Winston Churchill, Benjamin Franklin, to name a few. But if you think you’re going to inspire anybody by routinely working through the night, you might want to think again. Research published recently in the Journal of Applied Psychology shows that sleep deprivation has the specific effect of making it harder for us to charismatically inspire others. And in a double whammy, the research suggests that followers who are sleep deprived are likely to find it particularly difficult to be inspired by their leaders.

Christopher Barnes and his colleagues asked 88 business students to prepare a commencement speech (a talk meant to inspire students at their graduating ceremony), and then to deliver it in front of a video camera. Half of the participants made the speech in a state of sleep deprivation (the previous night they’d had to complete a survey every hour between 10pm and 5am), the others were fully rested.

Afterwards the students answered questions about their own performance, including their ability to engage in “deep acting” – regulating their emotions by reaching inward and trying to genuinely experience these emotions. Also, a team of judges watched the videos of the speeches and rated the students’ performances for charisma. The judges didn’t know who the students were, nor whether they were in the sleep deprived condition or not, but nonetheless they consistently rated the tired orators as less charismatic.

This result was just as Barnes and his team predicted because previous research has shown that sleep deprivation makes it harder to control our emotional displays, and that one component of charismatic behaviour is being able to embody gravity, enthusiasm, or righteousness as the situation demands. Bearing this out, sleep-deprived participants considered themselves less able during the speech to engage in deep acting. And the worse they felt they were at deep acting, the less charismatic the speech.

A second experiment turned the tables to see how observers deal with charismatic content when they are tired. The researchers cherry picked some of the more charismatic or uninspiring videos from the first experiment, and then asked 109 student participants to watch them back and rate each for their charismatic effect. Half of these participants were sleep deprived and they felt less charismatically impressed by what they heard. As this can’t be related to their own deep acting skills, what was going on? Again, the answer is emotion: the tired participants felt less positive, and this lower mood explained the degree to which sleep deprivation affected their ratings. This is because in searching for an external explanation for our feelings, we are liable to misjudge the source – in this case the students blamed their feeling flat from tiredness on the fact the orators weren’t that charismatic.

The tireless leader trope may not come out of nowhere: there is evidence for a gene that provides resistance to sleep deprivation, and the will to persevere during certain crises may temporarily outweigh the costs. But the costs – summarised here – can be substantial, including attention deficits, poorer decision making and risk evaluation, and memory lapses. Now we can add charismatic influence to that list. Moreover, role-modelling long hours risks propagating these habits to the rest of the organisation – so even leaders who have the rare ability to shake off their own tiredness will be presiding over cognitively impaired, irritable followers in no mood for their pronouncements. Forty winks are a wise investment indeed.


Barnes, C., Guarana, C., Nauman, S., & Kong, D. (2016). Too Tired to Inspire or Be Inspired: Sleep Deprivation and Charismatic Leadership. Journal of Applied Psychology DOI: 10.1037/apl0000123

–further reading–
Students: it’s time to ditch the pre-exam all-nighter
An afternoon nap tunes out negative emotions, tunes in positive ones

Post written by Alex Fradera (@alexfradera) for the BPS Research Digest.

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Smartphone study reveals the world’s sleeping habits

Middle aged men get the least sleep, the research found

Researchers in the USA have used a smartphone app to see how people’s sleep habits vary around the world. More specifically they’ve investigated how much the timing of sunrise and sunset affect people’s sleep times or if social and cultural factors are more important. “Quantifying these social effects is the next frontier in sleep research,” they write in the paper in Science Advances.

The study involved the ENTRAIN smartphone app which helps people recover from jet lag by recommending ideal levels of light exposure based on a user’s typical sleep routine. Users have the option to make their information available for research. Olivia Walch and her colleagues at the University of Michigan began collecting data from the app in 2014 and the new analysis is based on information sent in by 8070 users around the world during the first year.

Overall the data showed that a later sunrise goes hand in hand with later waking-up times, and that a later sunset is associated with people going to bed later, just as predicted based on how light affects the suprachiasmatic nucleus – the bundle of neurons behind the eyes that controls our sleep cycle, also known as the circadian rhythm. But crucially, the link between sunset and bedtime was weaker than biological explanations would predict.

Put differently, the time we get up is strongly influenced by the timing of sunrise, but the time we go to bed is not as strongly influenced by sunset, suggesting other social and cultural factors are involved. Consistent with this account, most of the cross-cultural differences in sleep – for example, the Dutch reported the most sleep and Singaporeans the least – were explained by later bed times in the countries getting less sleep.

The difference between the countries with the most and least sleep wasn’t huge: just under 7.5 hours for Singapore and just over 8.1 hours for The Netherlands. But the researchers emphasised that even a 30-minutes difference is meaningful, especially when you consider that sleep debt can have a cumulative effect over time.

Users of the app from the UK averaged about 8 hours sleep (a healthy amount) with average wake time just after 7 am and average bed time just before 11.15.

The researchers were also able to use the smartphone data to compare sleep habits by age, gender, and time spent exposed to natural light. Age was the most important factor with older people tending to go to sleep earlier. There was also much less variability in the sleep times of older users, which could because of biological mechanisms that narrow the window of opportunity for when it’s easy for older people to fall asleep.

This age-related finding could have everyday relevance – “being careful about how much light affects your circadian clock could be more and more important to sleep as you get older,” the researchers said. If your body’s only willing to sleep between fairly limited hours, you’re best off listening to it and switching off that TV.

Meanwhile, women were found to get more sleep than men – 30 minutes more, on average – thanks both to going to bed earlier and waking up later. The gender difference was greatest in mid-life so that middle-age men are the demographic group getting the least sleep, on average.

In terms of exposure to outdoor, natural light, app users who had more of this tended to report going to sleep earlier and sleeping more, which is as you’d expect based on the effect of daylight hours on the brain’s circadian clock.

The researchers concluded that their results “point to the suppression of circadian signaling at bedtime as an important target for clinical sleep intervention; and suggest that age-related differences in the window during which sleep can occur are evidenced on a global scale”. Aside from these specific insights into sleep, the group also said their findings show the power of modern smartphone technologies as a research tool. “”This is a cool triumph of citizen science,” said co-author Daniel Forger in a press release.

A global quantification of “normal” sleep schedules using smarphone data

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.

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Researchers have analysed the somniloquies of the world’s most prolific sleep talker

Album artwork for Dion McGregor Dreams Again

The “most extensive sleep talker ever recorded”, according to a new article in Imagination, Cognition and Personality, is the late American songwriter Dion McGregor. McGregor’s unusual sleeping behaviour – one commentator said he “sounds as if he were channeling Truman Capote on acid: flirtatious, slushy, disconnected from reality …” – first became public in the 1960s when McGregor shared a New York apartment with a posse of other artists and creative types. His song-writing partner and flat-mate, Mike Barr, became so fascinated by McGregor’s extensive somniloquies – most were over 100 words long – that he made more than 500 recordings of them, and they were released as a CD and book: The Dream World of Dion McGregor. Now a team of sleep experts led by Deirdre Barrett at Harvard Medical School have analysed 294 of these recordings to see how their content compares with typical dreams.

The researchers coded McGregor’s somniloquies for content using an established scale that is used for analysing dreams, and which includes checklists for characters, aggression, friendliness, sexual interaction, success, misfortune and good fortune. Then they used another scale that’s for coding the bizarreness of dreams, including elements of discontinuity (sudden changes in time and place or identity), incongruity (contradictions, such as saying a building has only one entrance, and then saying the building was entered a different way), and uncertainty and vagueness.

Compared with average dream scores on the scales, McGregor was more active in his somniloquies than most dreamers, while his sleep talk contained less aggression, less friendliness and less sex than usual dreams, fewer negative emotions, good fortune and success, but much more self-negativity and more female characters than is typical for men. His sleep talking was also less bizarre than the average dream, with fewer plot incongruities and contradictions.

The researchers provide this example to show a typical element in McGregor’s somniloquies, which while fantastical is not confused in plot or thought (unlike much typical dream content):

Oh, that doesn’t complete my collection at all! No! Oh no! Well let’s see, I have a dodo, and a rock, and a phoenix . . . oh dear! A pterodactyl, yes, the unicorn, the griffin, dear, oh yes, well a mermaid doesn’t count, she’s out in the pool! No . . . well, if she ever gets out I’m gonna mate her with the centaur! Yes! What do you think?! Certainly! Well, I don’t know. What do you think? Well, if you don’t mate them you know they’ll die off! (Tzadik Records, 1999, “The Collection”)

Album artwork for Dreaming Like Mad
With Dion McGregor

Other examples of content from McGregor’s sleep talking include him going door to door asking women if they have their favourite dress on, a roll call of people entering a hot air balloon for a moon trip (which ends after an encounter with sharp-beaked storks) and playing a game of “food roulette” with “a Lazy Susan of poisoned eclairs”.

The researchers think there are two explanations for the differences between McGregor’s somniloquies and typical dream content. One is that much sleep talking does not occur during dreams, and in fact people’s brain waves during sleep talking are distinct from those usually seen during dreaming, featuring fewer waves in the alpha frequency range, which they explained could be a sign of more frontal brain activity. The researchers further describe this as “an unusual state midway between waking and sleeping” (backing this up, there is a McGregor interview in which he says a sleep researcher recorded his brain activity during sleep talking and found a mix of sleep and waking brain wave patterns).

The other reason for the distinct content of McGregor’s somniloquies, the researchers believe, is simply to do with his personal characteristics: he was they say a quirky character with a self-deprecating sense of humour, he was likely homosexual, and he had an obsession with actresses (this last point could help explain the preponderance of female characters in his dreams). This perspective is consistent with the “continuity hypothesis” of dream content – the idea that “our actions and thoughts in everyday life also determine what we will dream about”.

Surprisingly little is known about the psychology and neuroscience of sleep talking and so this case study provides an intriguing addition to the literature. “Of course Dion McGregor is only one subject, so we can not generalise,” the researchers said, adding: “It would be interesting in future research to gather REM sleep-talking reports from a large sample of subjects to see if these differences from dream reports and continuities with waking traits consistently characterise talking from REM sleep.” For his part, McGregor was much more interested in his waking creative works (he sold songs to Barbara Streisand, among others) than his sleep talking: “it’s like being famous for wetting your bed,” he said.


Barrett, D., Grayson, M., Oh, A., & Sogolow, Z. (2015). A Content Analysis of Dion McGregor’s Sleep-Talking Episodes Imagination, Cognition and Personality, 35 (1), 72-83 DOI: 10.1177/0276236615574495

further reading
This guy turned surreal sleep talking into a cult album
Here’s a really simple trick that could help you enjoy more lucid dreams
Does dreaming of exam failure affect your real-life chances of success?
Older people have more black and white dreams

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.

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Here’s a really simple trick that could help you enjoy more lucid dreams

Lucid dreams are when you know you’re dreaming and you can consciously control events as they unfold: it’s like being the director and star of your own Hollywood movie. It’s estimated that about 20 per cent of people get to enjoy them fairly regularly (at least once a month). For the rest of us, a new study in the journal Dreaming suggests a really simple way to increase your odds of having lucid dreams – just start making more frequent use of the snooze function on your alarm clock.

Bethan Smith and Mark Blagrove at Swansea University surveyed 84 people who frequent various Facebook groups and online forums devoted to lucid dreaming. There were 44 women, 39 men, and their ages ranged from 18 to 75.

Based on the following definition of lucid dreaming as “occurring when an individual becomes aware that they are dreaming, and, while remaining asleep, can control some of the events or content of the dream,” 23 participants said they’d never had a lucid dream. The remainder gave an indication of how often they had lucid dreams on a 7-point-scale from 1 (less then once a year) to 7 (4-7 nights per week). To give you an idea of the spread of answers, 12 participants said they had less than one lucid dream per year, while 5 participants said they had between 4 and 7 per week.

One of the main findings to come out of the survey was a correlation between frequency of lucid dreaming and the number of times participants said they usually hit the snooze button on their alarm clock each morning. This correlation held even after controlling for the influence of other measures, such as the participants’ tendency to recall their dreams and their number of awakenings per night. Putting this finding slightly differently, people who reported using an alarm clock snooze function at all reported having significantly more lucid dreams than people who said they never used a snooze function (snooze-function users averaged 3.04 on the 7-point frequency of lucid dreaming scale compared with 2.76 among the non-snoozers).

We can’t read too much into these results – after all, perhaps for some reason, people who are more prone to lucid dreaming just happen to like using the snooze function on their clocks. To check that alarm clock snooze functions really cause more lucid dreams, we need an experiment that randomly allocates some people to start using the snooze function and then we could see if they start having more lucid dreams compared with a control group.

While caution is in order for now, the researchers explain that it does make theoretical sense that using the snooze function should lead to more lucid dreams. When people’s sleep is interrupted, such as by the snooze alarm, it’s more likely that they’ll dip straight back into a light REM sleep, which is when lucid dreams mostly occur. Indeed, if you use your alarm clock to help you doze and wake intermittently, this is very similar to an established method for inducing lucid dreams known as the “Wake-Back-To-Bed” technique, which involves scheduling an alarm to go off an hour before your usual waking time and then deliberately focusing on remaining lucid while falling back to sleep.


Smith, B., & Blagrove, M. (2015). Lucid dreaming frequency and alarm clock snooze button use. Dreaming, 25 (4), 291-299 DOI: 10.1037/drm0000012

further reading
How to nap

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.

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Look on the bright side – economic recessions mean workers get more sleep and free time

For understandable reasons, we usually think of economic slumps as bad times. But a new paper in The Journal of Occupational Health Psychology has uncovered a silver lining – during these periods, employed people enjoy more free time and more sleep.

Looking at patterns across American states between 2003 and 2010 – spanning the Great Recession which began 2007 – Christopher Barnes’ team found that worsening of the economy, as indexed by unemployment rates, was significantly related to workers sleeping more and spending more time enjoying leisure activities.

When the economy was at its lowest point, compared to its highest, workers were sleeping an average of ten minutes more per week and enjoying an extra 21 minutes of recreational activities. While this doesn’t sound like a lot, consider firstly that like all averages, some individuals may be enjoying much more than that, and secondly that such dividends may not be evenly distributed in time, but come as special bonuses – visiting an extra sports game each month, for instance, or avoiding a quarterly all-nighter, which is otherwise likely to spoil a run of following days.

The data, drawn from over 34,000 participants using an ongoing survey at the US Bureau of Labor Statistics, showed that the reason for this was simple: during economic dips, workers spend fewer hours on the job. There is unlikely to be a single reason for this: in some cases, companies will explicitly reduce employee hours to offset lower revenue, in others formal hours may be unchanged but workers simply find themselves with less to do. This joins other evidence that shows how macro-economic trends can effect people’s behaviour patterns: for instance, in poorer economic periods, workplace accidents drop in frequency, fewer people marry or divorce, but more children are conceived. In each case, the big picture shapes the little one.

When business picks up, that’s good news for organisations, but it demands that employees rein in the recharge activities important for their long-term engagement. Management should be aware of burnout risks during growth periods, and deploy resources to ensure that people aren’t sacrificing their life to sustain that growth. And during the low points, we should take heart that people are getting more opportunities for replenishing themselves. These breathing periods can be a chance to invest in activities with long-term benefits: to take up exercise and develop new skills. Or, simply, to enjoy some idle time.


Barnes, C., Lefter, A., Bhave, D., & Wagner, D. (2015). The Benefits of Bad Economies: Business Cycles and Time-Based Work–Life Conflict. Journal of Occupational Health Psychology DOI: 10.1037/a0039896

Post written by Alex Fradera (@alexfradera) for the BPS Research Digest.

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To keep your memories alive, it’s better to write a diary in the evening than in the morning

By guest blogger Jordan Gaines Lewis

For over 15 years now, I’ve faithfully kept a diary. Every night, from age 11 until my senior year of university, I snuggled into my bedsheets and rehashed the day’s events before nodding off to sleep. Even though I’m more likely to scribble down my thoughts just once or twice a week nowadays, I’ve found that writing in a diary before bed is a fun way to capture my memories – no matter how frivolous – to enjoy again years down the road.

Now a new study, published recently in The Quarterly Journal of Experimental Psychology, suggests that my nightly routine might help with something else: being able to recall a specific day’s events from memory weeks later. Importantly, however, I may be at a greater advantage than some diarists because I typically write in my diary just before hitting the pillow, instead of waiting until the next morning.

Cognitive psychologist Ágnes Szőllősi and her colleagues were interested in exploring how autobiographical memories, or personal memories of one’s life experiences, can be influenced by the time at which they’re recorded and consolidated. Because it’s known that sleep has a beneficial effect on learning and long-term memory formation, the authors hypothesised that people who recorded the day’s events in the evening just before bed would recall more events 30 days later than those who chronicled their day the next morning.

To test this, Szőllősi and her colleagues recruited 109 young adults between the ages of 18 and 25 to keep a written diary online. The age range was purposely narrow to control for circadian effects, as young people tend to perform better at tasks in the evening than older adults.

The participants were divided into three groups: those who recorded their notes in the evening, just before bed, about an event that they had experienced earlier that same day (Group 1); those who recorded in the morning, right after waking, an event from the previous day (Group 2); and those who recorded in the evening, just before bed, an event from the previous day (Group 3). In addition to keeping their diary for five consecutive days, participants also rated the personal importance of the events they’d written about (on a scale of 1 to 5), the duration of the events, and the amount of sleep they’d had the night before.

Thirty days later, all participants were instructed to describe as many of the previously-recorded events as they could, and how certain they were about their recollections (on a scale of 1 to 5). “Recall rate” was then calculated as the percentage of recalled events out of those recorded initially in the online diary.

Importantly, there were no differences between the groups in the way that they kept their diaries: the number of recorded events, the length of descriptions (word count), ratings of personal importance, and duration of the events, were the same for all three groups. Nor were there any group differences in the amount of time the participants reported sleeping.

And yet, recall rate was nearly 10 per cent lower in Group 2 – these were the participants who chronicled the previous day’s events in the morning after awakening – compared to the two evening groups. Despite differences in how the groups performed, however, the three groups scored similarly in ratings of certainty – in other words, the evening diarists didn’t seem to know their memories were more accurate. Also, the evening benefit applied to all event memories equally, regardless of their personal significance.

The researchers concluded that the time of memory reactivation (in this case, the time at which an event is described in a diary) affects how the memories are reconsolidated. But why? Szőllősi and her colleagues suggest that when a memory is in an “unstable” form (which is what happens after reactivation – in this case, after writing about an event in a diary), it’s vulnerable to interference. When participants wrote in their diary in the morning, interfering events that took place later in the day could disrupt the consolidation process. However, when done right before bed – whether on the day of the event or even 24 hours later – sleep may work to re-stabilise and consolidate these memories.

To examine this hypothesis further – and given the effect of age on circadian preference – it would be interesting to re-run this experiment in older adults, as they tend to perform better on memory and cognitive tasks in the morning compared to young adults.

The new results might be useful if you’re considering using a daily diary as a way to keep happy memories alive – such as on holiday, say, or charting a special period in your child’s development. By recording your reflections in the evening rather than the morning, you’ll be carving the memories deeper in your own mind.

However, my own motives are different – I’ll keep up my diary habit mostly because I’m eager to see how 50-year-old Jordan will eventually interpret the mind of 11-, 18-, and 25-year-old Jordans.


Szőllősi, A., Keresztes, A., Conway, M., & Racsmány, M. (2015). A diary after dinner: How the time of event recording influences later accessibility of diary events The Quarterly Journal of Experimental Psychology, 1-6 DOI: 10.1080/17470218.2015.1058403

Post written by Jordan Gaines Lewis, a PhD student at Penn State College of Medicine studying sleep and obesity in adolescents. She blogs about neuroscience at Gaines, on Brains. Follow on Twitter @GainesOnBrains

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