Are you feeling tired today? Much of the UK got up an hour earlier than usual this morning, following the start of daylight savings. But there’s evidence that the clocks changing can have much more serious effects too, including heart attacks and strokes.

There’s little doubt that British Summer Time (BST) brings benefits, including reducing energy usage nationwide by allowing us to make better use of daylight hours. This has led to repeated calls for BST to last all year round, to cut carbon emissions and let us enjoy more of the country’s limited winter afternoon sunshine.

The act of switching to daylight savings every year also seems to harm some people’s health. Studies have found an annual spike in  in Michigan in the US and in Finland the day after the clocks go forward in spring. Many of these deaths are likely to have been in frail, elderly people who are at the mercy of care staff schedules. But some could be due to loss of sleep: there’s evidence that heart attacks are most common on Mondays, possibly due to sleep lost while readjusting to the schedule of the working week.

The UK has tried year-round BST. The result was a large reduction in road casualties between 1968 and 1971, thanks to the lighter evenings, but the experiment was ended due to complaints from northern parts of the UK, where mornings were darker as a result.

Even more daylight

Many would like to see year-round BST reinstated. Some would even like to see our clocks pushed a further hour ahead in the summer, with the UK moving to the same time zone as Spain, which sits on the same line of longitude. According to a 2010 , such a move would give people in Birmingham an extra 301 hours of after-work sunlight each year. People around Glasgow and Edinburgh would get 175 extra hours, and even people as far north as Aberdeen should gain 159 hours. It is also likely to reduce the nation’s carbon footprint by about 2.2 per cent as people would need to use less electricity for lighting in the evenings, when they tend to be more active than in the early mornings.

Calls for year-round BST are championed by the , which says the move will reduce road deaths currently caused by darker evenings in autumn and winter. But several petitions pushing for change have failed, so the debate looks set to continue.

In the meantime, be careful: if you’re suffering from a loss of sleep, it may affect your work. A recent study that US federal judges mete out harsher sentences the day after the spring clock change, although we’ve previously noted that such studies should be taken with a pinch of salt.

Rest assured though that the physiological disruption from the clock change is short-lived. Our internal body clocks soon recalibrate, adjusting to our shifted sleeping and eating habits. But if you want to minimise the effects of switching to daylight savings next year, try going to sleep a little earlier each day in the run-up to the spring clock change.

Harness rebellion

Ever felt hungry and angry at the same time? There’s evidence that “hanger” is a real phenomenon, one that can affect your work and relationships.

The main reason we become more irritable when hungry is because our blood glucose level drops. This can make it difficult for us to concentrate, and more likely to snap at those around us.

Low blood sugar also triggers the release of stress-related hormones like cortisol and adrenaline, as well as a chemical called neuropeptide Y, which has been found to make people towards those around them.

This can all have an alarming effect on how you feel about other people – even those you love. A asked them to stick pins into “voodoo dolls” that represented their loved ones, to reflect how angry they felt towards them. The volunteers then competed against their spouse in a game, in which the winner could blast loud noise through the loser’s headphones.

The researchers tracked the participants’ blood glucose levels throughout. They found that when people had lower sugar levels, the longer the blasts of unpleasant noise they subjected their spouse to, and the more pins they stuck into their dolls.

But while being hungry really does change your behaviour, the effects of hanger have sometimes been overstated. One study that attracted attention a few years ago found that judges are less likely to set lenient sentences the closer it gets to lunch.

However, the findings from this study have never been replicated, and a by at the University of Hagen, in Germany, has suggested an alternative explanation. Harsher sentences may in fact be more likely towards the end of the morning because judges schedule simpler cases for this time. More complicated, lengthier cases carry a risk of running over into their lunch break. “Simulations show that the direct causal effects of eating on favourable rulings is overestimated by at least 23 per cent,” says Glöckner.

We won’t know for certain what causes the nasty judge effect until more research is done. But one thing is clear – it certainly isn’t advisable to make important decisions on an empty stomach.

Electing Trump

I know it’s wrong

Work it out

Isy Suttie has felt “head squeezing” since she was young. The comedian, best known for playing Dobbie in the British sitcom Peep Show, is one of many people who experience autonomous sensory meridian response (ASMR) – a tingly feeling often elicited by certain videos or particular mundane interactions. Growing up, Suttie says she had always assumed everyone felt it too.

Not everyone feels it, but Suttie is by no means alone. On Reddit, a community of share videos designed to elicit the pleasurable sensation. The videos, often described as “whisper porn”, typically consist of people role-playing routine tasks, whispering softly into a microphone or making noises by crinkling objects such as crisp packets. The most popular ASMR YouTuber, “Gentle Whispering”, has over 250 million views.  To most of us, the videos might seem strange or boring, but the clips frequently garner hundreds of thousands of views.

These videos often mimic real-life situations that provoke ASMR in susceptible people. Suttie says her strongest real-world triggers occur during innocuous interactions with strangers, like talking about the weather – “it’s almost as if the more superficial the subject the better,” Suttie says.

She feels the sensation particularly strongly when someone brushes past her. For Suttie, the feelings are so powerful that she often feels floored by them, and they even overcome pain and emotional distress. During a trip to the dentist, she still experiences the pleasurable tingles when the assistant brushes past her, she says.

Vanishing tingles

ASMR remains largely a mystery, but research is beginning to give us a clearer picture. The first formal of the phenomenon was published in 2015 by psychologists Emma Barratt and Nick Davis. They found that the sound of whispering is the most common ASMR trigger, followed by close personal attention like someone touching your face, then crisp sounds and slow and repetitive movements.

But recently, people have increasingly reported that their experience of ASMR is diminishing when they watch too many videos. The phenomenon has been dubbed “ASMR immunity” in on YouTube and around . Davis likens this to becoming desensitised to a stimulus, such as when drug users require larger doses to get the same hit.

The phenomenon of ASMR is being in a survey by physiologist Craig Richard at Shenandoah University in Virginia, which has so far received over 19,000 responses. Out of those with ASMR, 40 per cent answered yes when asked if their experiences had ever decreased or gone away.

But just as substance users take drug holidays to bring back the drug’s diminishing effects, taking a break can have a similar effect for people with ASMR, who commonly report the pleasant sensations returning after abstaining from the videos.

Richard says that, instead of immunity, it should be called tolerance. If they stop watching the videos for one or two weeks, most people say that the ASMR sensations normally return, he says.

Not quite euphoria

Richard’s preliminary results show that 95 per cent of those who experience ASMR feel it is something associated with the head and brain, and 71 per cent believe they feel the sensation in the area around their spinal cord.  Richard has received responses to his survey from more than 100 countries, implying the condition isn’t just a cultural phenomenon limited to certain locations.

While the sensation is often described as euphoric in the media, only 35 per cent of the ASMR-experiencing respondents to Richard’s survey would describe it this way. Instead the most popular term used to describe it was “relaxing”, and 60 per cent said ASMR makes them feel sleepy, suggesting people are using the whispery videos to relax.

Despite assumptions that the feeling may be sexual, only 10 per cent of respondents said they felt their experience of ASMR is sexually arousing.

Psychologist Stephen Smith at the University of Winnipeg in Canada recently ASMR by comparing fMRI brain-scans of people who experience the sensation with scans from volunteers who do not. He found that people with ASMR had more “cross-talk” between brain networks. The study was only small, but it offers the first clue as to how the wiring of our brains make some of us able to experience these mysterious tingles.

Big differences

Better psychiatric care

A nudge uses an understanding of human behaviour to encourage people to do particular things. Nudges work without imposing rules or big penalties – they are more subtle approaches for promoting certain actions.

The term was coined in 2008 by Richard Thaler at the University of Chicago and Cass Sunstein at Harvard University. Since then, politicians around the world have become enchanted by the idea, with the UK government even establishing a “nudge unit”. Formally known as the Behavioural Insights Team, it has used large randomised controlled trials to formulate advice on everything from to .

In one study, the team found that rephrasing the message on the UK government’s organ donor website . The original message politely asked people to join the register, but changing it to “If you needed an organ transplant, would you have one?” helped boost the sign-up rate by the equivalent of 96,000 extra registrations a year.

But is it ethical to alter people’s behaviour in this way without their knowledge? The UK’s nudge unit has for moving to private ownership – a move which means it is no longer subject to freedom of information requests.

Perhaps this ethical quandary can be avoided, because an explicit nudge can work, too – a finding that counters the ideas of philosopher Luc Bovens at the London School of Economics, who had suggested that nudges work best . Now Hendrik Bruns at the University of Hamburg, Germany, and his team .

Donation game

The team gave student volunteers €10 each and asked them how much, if any, they would like to donate to a fund to protect against climate change. Any money they didn’t donate would be theirs to keep.

Some of the volunteers were told no extra information, while others were told that the default donation was €8, a move inspired by studies that have found that default options influence economic decision-making. But some of these volunteers were also told that the preselected default might have been chosen to influence their behaviour – whereas others were told that it was definitely picked for this purpose. A fifth group was told that the default may have the power to influence their decision, and that it had been purposely picked to increase the amount they gave.

It turned out that the average donation for those who were nudged was €2.87, compared with only €1.67 for those who weren’t told of any default. None of the suggestions that the default may change behaviour had a significant effect on the power of the nudge. People who weren’t in the dark still donated more money.

Their findings are supported by . In one study, researchers found they could nudge people into choosing healthier snacks next to the cash register in shops – and that by an accompanying sign reading “we help you make healthier choices”.

This line of research echoes growing evidence that placebos work even if we know they are fakes. This was first demonstrated in people seeking treatment for irritable bowel syndrome, and has recently turned up again in a .

The fascinating lesson seems to be that nudges and placebos do not depend simply on trickery and deception, and can work in the light of day.

That’s not to say, though, that openness will be embraced by all. The next time you fill in a form online and see that a box has been checked by default, take a moment to consider if you really want to opt into that mailing list.

It can seem like barely a week goes by without a new study linking the stage in a woman’s monthly cycle to her preferences in a sexual partner. Reportedly, when women are ovulating they are attracted to men who are healthier, more dominant, more masculine, have higher testosterone levels– the list goes on. But do women really exhibit such behavioural changes – and why are we so fascinated by the idea that they do?

A popular theory in evolutionary psychology is that women seek out men with better genes while they are ovulating to have short term affairs with, so as to produce healthier babies. These men may not necessarily stick around for the long haul, but appear particularly attractive when a woman is in the fertile stage of her cycle. During the non-fertile phase, the theory goes that women seek out men who are more likely to make reliable long-term partners and good fathers.

But something smells a bit fishy here. Are women really evolutionarily hard-wired to cuckold their partners? Or might the attraction of a salacious hypothesis – with slightly sexist overtones – be shaping some of this research?

Masculine all month

A review of these kinds of studies is now challenging this often-told story. Wendy Wood at the University of Southern California and her team have analysed 58 studies – some of which were never published – and found that .

Overall, the researchers found that women do prefer men with dominant, masculine, healthy traits, and more symmetrical faces. However, there was no link between ovulation and a woman’s desire for short-term sexual encounters or longer term relationships.

So why have we been telling this sexy story for so long? The team found that while early tests of this hypothesis found strong effects, more recent studies have been detecting smaller effects or no association at all. This kind of trend is typical when an original finding is a false positive, and subsequent studies struggle to replicate the result in more rigorous, carefully controlled experiments.

Taking a closer look, the team found that the experiments that reported strong associations between menstrual cycle phase and attraction traits tended to use broader, less precise measurements and definitions. Instead of using hormone tests and other careful measurements, these studies usually classified women into large “fertility windows”, which may or may not have accurately captured when they were ovulating.

As is often the case in behavioural psychology research, the team found that studies that failed to find the ovulation effect were less likely to be accepted by a journal for publication.

Menstrual sync-up

Another popular theory is that when women live together, . The idea has become a popular example of how pheromones can control us, but over time many studies have failed to replicate and confirm the finding.

But for some reason, this idea is particularly resilient to debunking, in an abundance of and anecdotal conversations between friends. However, why you may have noticed an apparent synchronisation in your own life.

If we imagine two women with cycles of 28 days, the maximum amount of time they could be out of synch would be 14 days. On average, we would expect them to be only seven days apart, with a 50 per cent likelihood that they are even more closely aligned, just through chance alone. If we assume menstruation lasts five days, it’s hardly surprising that in a group of close friends, there will be some overlap.

Female fascination

Under scrutiny, the sheer volume of studies examining every little quirk in the context of a woman’s menstrual cycle starts to feel a little ridiculous. For example, a study this month reported that men are slightly better than women based on the sound of her voice.

Why are so many studies done in this area? Wood suggests it’s because menstruation is a clear sign of a biological process, and carries a lot of cultural meaning. “It’s been interpreted within religious contexts throughout history. It’s the obviousness of the biology that draws people to try to understand what effect it has on women’s experiences.”

But this fascination with menstruation errs when it assumes too much about women’s behaviour. “The challenge has been the oversimplified notion that if you study women’s menstrual cycles, you learn something directly important about their social judgments,” says Wood. “It turns out to be much more complicated than that.”

Based on the growing body of unreplicable research in this area, it’s best to take new findings like these with a pinch of salt. But the popularity of such theories of female behaviour and sexuality mean the menstruation myths are unlikely to be going away anytime soon.

Telling a story

Blinding bias

Racial prejudice?