Having worked as a writer, I have realized that there isn’t any average Tuesday. Some days, I will work like a man on a mission (or zoomies!); on other days, there is not enough Red Bull to give me wings. Funny thing is, a study from the University of Toronto reveals it isn’t just me or my personality, the mental ‘ups’ and ‘downs’ are hardwired in everyone. Researchers found that when people are thinking clearly, they can roughly do 40 extra minutes of productive work.
The research, published in Science Advances, tracked participants for 12 weeks to understand why people struggle to follow through on their plans. The findings point to fluctuations in mental sharpness as a key factor that separates the good days from the ones where simple tasks seem cumbersome. When the participants were more alert, they were more likely to set goals and complete them, be it schoolwork or running errands.
Scientists wanted to understand why everything clicks on one day, while another day is full of struggle—and whether mental ups and downs actually matter.
What Really Is Being Mentally Sharp?
Mental sharpness refers to how clear, focused, and efficient a person’s thought processes are at a given period of time. People concentrate easily when they are sharp and make quicker decisions. It becomes easier to follow through with their to-do list for the day. However, when mental sharpness declines, even simple and routine tasks can feel difficult.
Instead of comparing different people, the research team followed the same individuals over time to observe changes within each person that influenced their daily efficacy. Participants were all university students, and they were asked to complete short daily tests that measured how quickly and accurately they could think. They also reported on their goals, mood, productivity, sleep, and workload— all of which are linked to mental sharpness. The in-depth study helped researchers to link mental sharpness directly to real-world outcomes rather than general averages.
The Brain doesn’t work the Same Way Every Day
The results showed a clear pattern that was consistent regardless of personality traits. Students completed more goals and were more ambitious on sharper days, but when sharpness dipped on another day, simple tasks became harder.
While qualities like grit or self-control influenced overall performance, they didn’t prevent less productive days. Hutcherson aims to capture what separates the good days from the bad ones. And she actually has an answer—along with tips to improve productivity.
What Influences Daily Sharpness?
Mental sharpness is more like a sprint than a marathon, subject to short-term changes that can affect performance. Students tended to perform better after getting more sleep than usual and earlier in the day. Feeling motivated boosted sharpness, while depressive moods led to decreased levels.
Workload was a mixed bag. Putting in long hours on a single day was associated with greater sharpness, suggesting that sudden demands can boost mental acuity. However, overworking had the opposite effect, reducing mental sharpness and making it difficult to stay productive.
Hutcherson calls this a trade-off. A hard push for a day or two is fine, but a grind with no breaks for too long is a recipe for disaster. While this research and many other studies advocate for the need to rest, a 17th-century proverb already warned us of burnout:
“All work and no play makes Jack a dull boy.”
Tips to Support Productivity and Mental Sharpness
The study focused on university students, but its findings can be applied more broadly. The data points to practical ways people can improve their chances of having more productive days.
“From our data, there are three things you could do to try to maximize mental sharpness: getting enough sleep, avoiding burnout over long periods of time, and finding ways to reduce depressive traps,” says Cendri Hutcherson, associate professor in the Department of Psychology at the University of Toronto Scarborough and lead author of the study.
She also stresses being patient with yourself when you’re not as productive as you would like. She advises embracing a dip in productivity and giving yourself some slack.
Final Reveal: How much Better Are the Good Days?
Mental sharpness is not a vague term lazily put without real-world impact. By analyzing cognitive performance over hours of work, researchers estimate that being above or below the usual levels of sharpness can shift productivity by about 30 to 40 minutes in a single day, with the gap between the best and worst days amounting to 80 minutes of work.
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