With all the talk about self-improvement these days, people don't pay enough attention to self-worsening. In fact, there are many common behaviours that have been shown in one or more studies to make people stupider.
We've compiled a list of things that decrease intelligence or IQ or cause neurological decline, and you can start by turning off most TV shows.
Watching reality TV
An Austrian study showed participants a reality-like show and asked them to take a knowledge test immediately afterward. Those participants fared worse than those who had not seen the reality show beforehand.
A UCLA study showed that steady sugar consumption for as little as six weeks "slows the brain, hampering memory and learning." According to Choice magazine, about 80 per cent of the sugars we eat are in low-nutrition foods we buy such as soft drinks, juices, fruit-based drinks and sports drinks.
Research conducted at Stanford University in 2009 shows that multitaskers "who are regularly bombarded with several streams of electronic information do not pay attention, control their memory or switch from one job to another as well as those who prefer to complete one task at a time."
A series of three experiments conducted by Cardiff University in Wales determined that chewing gum "impairs short-term memory for both item order and item identity."
Watching FOX News
A 2011 study by Fairleigh Dickinson University found that people who watch Fox News are less likely to be knowledgeable about the political landscape than those who watch MSNBC, Jon Stewart's The Daily Show or NPR.
"Fox News viewers are significantly more misinformed than consumers of news from other sources," a 2010 University of Maryland study showed.
A 2010 Kent State University study tested more than 100 obese individuals before and after they had bariatric surgery. Men's Health reports that "before the surgery, most subjects showed below-average memory skills. But 12 weeks after surgery...their memory test scores had improved to within the average range for all adults."
Researchers at Cal Berkeley changed the sleep schedule for hamsters every three days for a month and the hamsters produced 50 per cent fewer neurons than they did on a normal sleep schedule.
A recent study performed by Environmental Health Perspective, a journal published by the National Institute of Environmental Health Sciences, concluded that "children in high-fluoride areas had significantly lower IQ scores than those who lived in low-fluoride areas." Fluoride is commonly added to most drinking water.
In businesses around the world, it's fairly common to toss ideas around at meeting to help stimulate creative and productive activity. But a Virginia Tech study revealed that "group settings can diminish expressions of intelligence, especially among women." Social feedback in settings ranging from jury deliberations to cocktail parties "had a significant effect" on the subjects' problem-solving abilities.
Being spanked as a child
A wide-ranging study by the University of Manitoba found that more than five per cent of all mental disorder is caused by being spanked or other forms of childhood physical abuse. "This type of punishment was associated with poor mental outcomes and several mental disorders almost uniformly across the board," said Tracy Afifi, the founder of the study, according to WebMD.
If you believe the US Army, PowerPoint presentations are making us stupid. Commanders in the Army told the New York Times in 2010 that the Microsoft program "stifles discussion, critical thinking and thoughtful decision-making."
A 2011 study by the journal Pediatrics showed that children who watched fast-paced cartoons like SpongeBob performed poorer at a mental test than those who watched an educational show or those who drew. "Children who watched 9 minutes of a fast-paced cartoon," SpongeBob, in the study's case, "had impairment in their executive function compared with children who were assigned a drawing task and those who watched educational television."
In addition to the numerous other harmful effects secondhand smoke causes, children who are exposed to enough of it could end up with lower IQs and lower achievement in school and on test scores, according to Central Michigan University.
The Yale Stress Centre concluded this year that stressful situations "can reduce the number of connections between neurons in the brain and impair the ability of managing tense events in the future," as reported by The Morning Call. Cumulative stress, Yale found, can cause a decrease of gray matter in the brain's prefrontal cortex and "can impair the brain's ability to store information and respond to the environment."
Ambien and Xanax
If you're an older individual, taking Ambien (a sleeping pill) and Xanax (used to ease stress and anxiety) could become extremely harmful, according to doctors at AARP. These drugs could cause "memory loss (even amnesia), dementia and suicidal thoughts" among users and "both Xanax and Ambien slow down the central nervous system."
Lack of iodine
You don't need much iodine in your system, but it's crucial to have before you're born. In the prenatal stage, an iodine deficiency "can lead to serious physical and mental disorders," according to Steady Health. In fully developed adults, an iodine deficiency can lead to a 13 point decrease in IQ.
Smoking weed consistently from adolescence causes "neuropsychological decline broadly across domains of functioning, even after controlling for years of education," according to research from Duke University. Even stopping the habit for a long period of time "did not fully restore neuropsychological functioning among adolescent-onset cannabis users. Findings are suggestive of a neurotoxic effect of cannabis on the adolescent brain."