If there's any holiday that comes close to a celebration of the brain, it's April Fools' Day. Neuroscientists dedicate their careers to studying how the mind functions. This field of study covers a variety of questions we might ask about ourselves: How do we form memories? Why do we dream? What is consciousness?

Answering any one of these questions could take a lifetimes of study across a range of disciplines. But given the holiday in which we find ourselves, why not look to science currently out there on this question: What makes us stupid?

PHOTOS: Stupid Inventions of the Past

Even defining "stupidity" from a neurological standpoint can be difficult. In describing each of the studies below, the term applies to defining a subject who has either exhibited a cognitive decline from a control state, or engaged in risky behavior as a result of improperly evaluating risk. Or both.

Given the health risks associated with consuming a high-fat diet, there's no doubt that regularly eating unhealthy foods isn't a very smart idea. But according to researchers at Oxford University, eating lots of high-fat foods can impair cognitive abilities.

Published in 2009 in FASEB Journal, the study examined the effects of an extended high-fat diet on rats. While being fed a standard, low-fat diet, the rats were tested on their ability to make their way though a maze. This gave researchers a baseline for their short-term memory. Later, the rats ran the same maze after nine days on a high-fat diet and were making more mistakes.

In addition to inhibiting the mental capacities of the test animals, the researchers noted that the diet also affected them physically, making them less able to endure exercise on a treadmill. By the fifth day of the diet, the rats were running 30 percent the distance they were originally. By the ninth day, they were running half as far as they did on the standard diet.

Why Teenagers Act So Stupid

Although teenagers themselves may disagree with the assessment, studies have shown that teens can be impulsive risk-takers. In other words, they are often inclined to act without thinking.

The teen brain is hardwired to overestimate reward and undervalue risk, according to a study published in January 2011 in the Journal of Neuroscience. This lack of impulse control may explain why teens are more vulnerable to drug and alcohol addiction, as well as some psychological disorders, according to the study's authors.

NEWS: Does the Internet Make You Dumb?

The Internet may contain the largest archive of information in human history. That doesn't mean, however, that we're getting smarter as a result of our near-ubiquitous access to the Web.

While the net effect of the Internet on human intelligence is still the subject of debate, science and technology experts contend that our brains are being rewired as a result of our constant access to information. The Internet essentially serves as an external brain, functioning as a kind of second memory.

Why Does Alcohol Make You Behave Differently?

We've all been there. You've had a few too many (and a few more after that) and done something incredibly stupid, but you can't seem to figure out why.

Researchers at the University of Adelaide may have an answer. They found that immune cells in the brain are involved in behavioral responses to alcohol. This immune response makes it increasingly difficult for someone who has consumed alcohol to control muscles involved in walking and talking, according to a release on the study.

So when you pick up the phone the following day to start the apology tour after acting out in a drunken stupor, don't chalk up your abnormal behavior to alcohol. Go ahead and blame it on your immune system.

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