Among the countless habits we pick up, there are 10 surprising things that can quietly chip away at our mental sharpness, leaving us a little slower on a trivia night or a pop‑quiz.

Why These 10 Surprising Things Matter for Your Mind

10 Dim Lighting

Researchers at Michigan State University uncovered a link between low‑intensity lighting and a weakened capacity for memory and learning.

In the study, scientists worked with Nile grass rats, which, like humans, are diurnal. The rodents first learned to navigate a maze, then were divided into two groups: one basked in bright daylight, the other was kept under dim lighting.

After a month, the rats confined to dim light showed a 30 percent loss of hippocampal volume – the brain region crucial for learning. When re‑tested on the same maze, the dim‑light group performed worse than before, whereas the bright‑light group actually improved.

The dim lighting conditions mirror the typical indoor illumination found in most homes and offices.

9 Smartphones

Smartphones keep us glued to a constant stream of notifications, and that tether can drain our cognitive stamina.

At the University of Texas, a team studied roughly 800 regular phone users. Participants were asked to complete a series of computer‑based attention tests. Some left their phones in another room, while others simply muted the devices and left them face‑down on the desk.

Those who stashed their phones elsewhere outperformed the desk‑bound group by a significant margin. The researchers concluded that merely having a phone within sight taxes the brain’s focus, forcing a subconscious battle against the urge to check messages.

This mental tug‑of‑war saps the energy that should be directed toward the task at hand. Removing the phone entirely gives the subconscious a much‑needed breather.

8 Processed Food

A diet heavy on processed snacks during early childhood can leave a lasting dent in cognitive performance.

Researchers examined the eating habits and later IQ scores of about 14,000 youngsters. Children who ate mainly processed foods at age three scored lower on average IQ tests five years later than peers who enjoyed nutrient‑rich meals.

Vitamins and essential nutrients nurture optimal brain development, while processed junk offers little benefit. Because the brain grows most rapidly in the first three years, nutrition during this window has a profound, lasting impact.

Even when those same children later switched to healthier diets, the earlier reliance on processed foods did little to close the IQ gap.

7 Multitasking

Many studies have shown that multitasking is a cognitive illusion – the brain simply flips back and forth between tasks at breakneck speed.

Stanford researchers asked participants to rate their own multitasking prowess, then put those same people through a battery of focus‑intensive tests. The self‑proclaimed multitaskers actually performed worse than those who preferred to concentrate on one thing at a time.

Beyond poorer task performance, juggling multiple streams of information can temporarily shave about ten points off an IQ score, a dip larger than the drop seen after smoking marijuana or losing a night’s sleep.

In short, trying to do many things at once ends up doing none of them well, and it costs your brain a measurable intelligence hit.

6 Sugar

A diet swamped with fructose can blunt mental acuity in as little as six weeks.

At UCLA, scientists taught rats to navigate a maze, then split them into two groups. Both groups drank fructose‑laden water, but one group also received omega‑3 fatty acids, which are thought to shield brain cells.

After six weeks, the omega‑3‑supplemented rats out‑performed their counterparts, who struggled to recall the maze route and showed reduced synaptic activity.

Fructose spikes insulin and messes with the brain’s fuel‑use pathways, hampering neuronal communication. Fortunately, omega‑3s appeared to counteract the damage, suggesting a salmon‑after‑ice‑cream treat could keep your IQ from nosediving.

5 A Long Commute

Spending more than two hours behind the wheel each day can steadily erode cognitive function.

Researchers at the University of Leicester tracked over 500,000 participants for five years, testing memory and intelligence at multiple points. Of those, about 93,000 logged daily drives exceeding two hours.

Long‑distance commuters started off with lower baseline scores and showed a gradual decline in cognitive ability over the study period.

The brain receives far less stimulation while cruising on autopilot, a factor also observed in people who binge‑watch television for three or more hours a day.

4 Jet Lag

Jet lag isn’t just a temporary feeling of disorientation; it can have lingering effects on memory and learning.

Scientists at UC Berkeley used hamsters to model chronic jet lag, shifting their light‑dark schedule by six hours twice a week for a month – mimicking the rhythm of frequent international travel.

During the simulated jet‑lag periods, the hamsters performed poorly on maze and learning tasks. Even a month after returning to a regular schedule, they continued to lag behind control animals.

Post‑mortem analysis revealed that jet‑lagged hamsters possessed only half the number of hippocampal neurons compared to the rested group, a deficit that persisted weeks after normal sleep resumed.

Anyone who routinely flips between time zones or works rotating night shifts may suffer similar hippocampal damage.

3 Obesity

Carrying excess body fat can interfere with the way the brain processes information.

In a study of 17 obese women, brain scans showed faster sugar metabolism compared with a control group of average‑weight women. The participants underwent cognitive testing before and after bariatric surgery.

Post‑surgery results revealed marked improvements, especially in executive functions such as planning and organization.

Further research involving nearly 500 adults found that overweight individuals possessed less white‑matter volume than their lean counterparts. White matter is the brain’s communication highway, linking different regions.

While white‑matter naturally declines with age, the loss accelerates in middle‑aged and older adults who are overweight. A 50‑year‑old with obesity exhibited white‑matter volume akin to a typical 60‑year‑old.

2 Being Spanked As A Child

A U.S. study found that children who experienced corporal punishment scored lower on IQ tests than their non‑spanked peers.

Researchers followed two age cohorts: children aged two to four and those aged five to nine. Each group was tested for cognitive ability, then retested four years later.

In the older cohort, spanked children averaged almost three IQ points lower than the control group. The younger cohort showed an even larger gap – about five points.

Cross‑national data echoed these findings: countries with higher spanking prevalence tended to have lower average IQ scores.

Scientists attribute the correlation to chronic stress; repeated swats can make children more jumpy and fearful, conditions linked to reduced intellectual performance.

Fortunately, corporal‑punishment rates are declining worldwide, and researchers anticipate a gradual rise in global IQ averages as a result.

1 Dumb TV Shows

What you watch on the couch can directly influence how sharp you think.

While some programs are educational, a slew of low‑brow reality shows offer little intellectual nourishment. Moreover, researchers have shown that these mindless shows can actually make viewers dumber.

Psychologist Markus Appel gave college students a short story about a hapless character making terrible decisions. After reading, those students performed worse on subsequent cognitive tests than peers who read a neutral story.

Appel attributes the effect to “media priming,” where exposure to certain content subtly shifts thought patterns and behavior. In other words, binge‑watching a brain‑draining series can spread its stupidity to the viewer.