Timing is everything. For early risers and late-nighters alike, listening to your internal clock may be the key to success. From the classroom to the courtroom and beyond, people perform best on challenging tasks at a time of day that aligns with their circadian rhythm[1].
Circadian rhythms[2] are powerful internal timekeepers that drive a person’s physiological and intellectual functioning throughout the day. Peaks in these circadian rhythms vary across individuals. Some people, known as larks or morning chronotypes, peak early and feel at their best in the morning. Others, known as owls or evening chronotypes, peak later in the day and perform best in the late afternoon or evening. And some people show neither morning nor evening preferences and are considered neutral chronotypes.
As a researcher[3] seeking ways to improve cognitive function, I’ve explored whether your chronotype affects your mental performance. Understanding the kinds of mental processes that vary – or remain stable – over the course of a day may help people schedule their tasks in a way that optimizes performance.
Why your chronotype matters
Chronotype can be measured with a simple questionnaire[4] that assesses things like your perceived alertness, preferred rising and retiring times and performance throughout the day. Even without a questionnaire, most people have a sense of whether they are a lark or an owl or fall somewhere in between. Do you wake up early, without an alarm, feeling sharp? Are you mentally drained and ready for pj’s by nine? If so, you are likely a morning type. Do you sleep late and wake feeling sluggish and foggy? Are you more energized late at night? If so, you are likely an evening type.
People perform best on many challenging mental tasks – from paying attention[5] and learning[6] to solving problems[7] and making complex decisions[8] – when these actions are synchronized with their personal circadian peaks. This is known as the synchrony effect[9]. Whether you are an air traffic controller scanning the radar, a CFO reviewing an earnings report or a high school student learning chemistry, synchrony can affect how well you perform.
Much of the evidence for synchrony effects comes from lab studies that test both larks and owls early in the morning and late in the day. People with strong chronotypes are more vigilant[10] and better able to sustain attention[11] at their peak relative to off-peak times. Their memories are sharper, with better list recall[12] and more success in remembering “to-do” tasks[13] like taking medication.
People are also less prone to mind wandering[15] and less distracted at their optimal time. For example, a study I conducted gave participants three weakly related cue words (such as “ship,” “outer” and “crawl”). They were tasked to find another word that linked all three (such as “space”). When my team and I presented misleading words alongside the cue words (such as “ocean” for ship, “inner” for outer and “baby” for crawl), those who were tested at synchronous times were better at ignoring the misleading words[16] and finding the target solution than those who weren’t.
The basic mental abilities that are affected by synchrony – including attention, memory and analytical thinking – are all skills that contribute to academic success. This connection is especially significant for teens, who tend to be night owls[30] but typically start school early.
One study randomly assigned over 700 adolescents to exam times in the early morning, late morning or afternoon. Owls had lower scores[31] relative to larks in both morning sessions, but this disadvantage disappeared for owls taking the exam in the afternoon. Early start times may put student owls a step behind larks.
Time of day may also be a consideration when conducting assessments for cognitive disorders like attention-deficit disorder or Alzheimer’s disease. Scheduling time may be particularly significant for older adults, who tend to be larks[32] and often show larger synchrony effects[33] than young adults. Performance is better at peak times on several key neuropsychological measures[34] used to assess these conditions. Failing to consider synchrony may affect the accuracy of diagnoses and subsequently have consequences for clinical trial eligibility and data on treatment effectiveness.
Of course, synchrony doesn’t affect performance on all tasks or for all people. Simple, easy tasks – like recognizing familiar faces or places, dialing a close friend’s phone number or making a favorite recipe – are unlikely to change over the day. Furthermore, young adults who are neither larks nor owls[36] show less variability in performance over the day.
For those who are true early birds or night owls, tackling the toughest mental tasks at times that align with their personal circadian peaks could improve their outcomes. When small improvements in performance offer an essential edge, synchrony may be one secret to success.
Curious Kids[1] is a series for children of all ages. If you have a question you’d like an expert to answer, send it to This email address is being protected from spambots. You need JavaScript enabled to view it.[2].Why do our noses get snotty when we are sick? – Veronica P., age 5, Panama City, Florida Not many things are as uncomfortable and annoying as a runny or congested nose when you’re sick. Constantly blowing your nose and not being able to breathe through it may leave you wondering: Why does this happen? I’m a nurse practitioner who works with kids every day and also teaches nursing[3]. The answer is pretty simple. Mucus – or snot – is one of the ways your body helps keep you healthy. Mucus lines your nose, throat, lungs and other parts of your body to protect it from bad bacteria, viruses and other particles. Your body continuously creates mucus[4] to fight off germs and help get rid of them. When you’re sick, your immune system ramps up to produce extra mucus to flush out germs. While it might seem gross, mucus is also pretty amazing.Slimy protectorYour body creates mucus out of a combination of water, proteins and salts[5]. Its sticky consistency traps bad microorganisms and other unwanted particles, like dust, pet dander and mildew, so they can’t get farther into your system. Some components in mucus stop bacteria from banding together[6] and becoming more dangerous. Other elements can actually kill the invaders[7] that are trying to make you sick. And though scientists don’t completely understand how, the proteins and genes in mucus[8] seem to work together to make it thicker and stickier if necessary.Once germs or other potentially damaging particles are trapped and neutralized, your body’s way of getting rid of them altogether is to make so much mucus that you have to blow, sneeze or cough them out. You might have noticed that sometimes when you’re sick, your nose can get red too. This is because your immune system, in addition to making mucus, also sends extra white blood cells to the source of an infection. As they rush to the scene to help fight infection, the extra white blood cells expand the blood vessels[9] in the area, making your nose look red. All the wiping and blowing can make it red, too.
The mucus rainbow. Children's National Hospital[10], CC BY-NC-SA[11] Snot can come in a rainbow of yucky colors. When white blood cells are fighting an infection, they release chemicals that may turn your snot yellow[12]. When more of those cells are needed to get the job done, mucus can even turn green. Typically, after a few days, colored mucus changes back to clear and your stuffy nose will go away. Not just in your noseMucus isn’t found just in your nose and lungs.Your eyes also have a thin layer of mucus[13] that helps protect them from particles in the air. When you get sick or get an eye infection, eye mucus[14] can act the same way it does in your nose – catching and killing germs. Eye mucus can also sometimes turn thick and yellow. If that happens, you’ll want to call your health care provider. Don’t ever touch your eyes with your fingers. That can introduce more germs[15].Your stomach and intestines also have protective mucus. If you’ve ever had an upset stomach that led to diarrhea, the mucus in your intestinal track was working overtime to help flush out bad bacteria[16]. That’s why your normal poop goes from a solid mush to something more slimy. There are other reasons you can have stomachaches – like stress, constipation or food allergies – but if you have diarrhea, your mucus is definitely hard at work. Animals have it tooHumans aren’t the only animals that use mucus. For example, dogs and cats have mucus[17] too.
Some fish use mucus for protection while sleeping. RobertoCostaPinto/WikiMedia Commons[18], CC BY-SA[19]Parrotfish[20], wrasses[21] and other sea creatures[22] produce mucus cocoons to help protect them from predators at night. Chameleons use the sticky mucus on the end of their tongues[23] to reel in their prey. Earthworms secrete mucus to help them move through the soil, which in turn benefits the soil[24].In humans, mucus helps neutralize and eliminate the microbial bad guys. So the next time you reach for a tissue to blow your nose, remember: Your body’s natural defenses are doing their best to keep you healthy or make you better. Just think of all that snot as one of your body’s superpowers.Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to This email address is being protected from spambots. You need JavaScript enabled to view it.[25]. Please tell us your name, age and the city where you live.And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.