Some misconceptions

Human body and health

Different tastes actually can be detected on all parts of the tongue by taste buds, with slightly increased sensitivities in different locations depending on the person, contrary to the popular belief that specific tastes only correspond to specific mapped sites on the tongue. The original tongue map was based on a mistranslation by a Harvard psychologist of a discredited German paper that was written in 1901.

There is no single theory that satisfactorily explains myopia—in particular, studies show that so-called eyestrain from close reading and computer games does not explain myopia. There is also no evidence that reading in dim light or sitting close to a television causes vision to deteriorate.

Shaving does not cause hair to grow back thicker or coarser or darker. This belief is due to the fact that hair that has never been cut has a tapered end, whereas, after cutting, there is no taper. Thus, it appears thicker, and feels coarser due to the sharper, unworn edges. Hair can also appear darker after it grows back because hair that has never been cut is often lighter due to sun exposure.

Hair and fingernails do not continue to grow after a person dies. Rather, the skin dries and shrinks away from the bases of hairs and nails, giving the appearance of growth.

Although there are hair care products which are marketed as being able to repair split ends and damaged hair, there is no such cure. A good conditioner might prevent damage from occurring in the first place, but the only way to get rid of split ends after they appear is by a hair cut.

Snapping or cracking one's knuckles does not cause arthritis.

Sugar does not cause hyperactivity in children. Double blind trials have shown no difference in behaviour between children given sugar full or sugar-free diets, even in studies specifically looking at children with attention-deficit/hyperactivity disorder or those considered "sensitive" to sugar. In fact, it was found that the difference in the children's behaviour was all in the parents' minds.

It is a common misconception that sleepwalkers should not be awakened. While it is true that a person may be confused or disoriented for a short time after awakening, it is actually quite dangerous not to wake a sleepwalker as they may injure themselves if they trip over objects or lose their balance while sleepwalking. Such injuries are common among sleepwalkers.

While the vitamin A in carrots does help to build healthy vision (among other things), it does not improve the eyesight of a person already in possession of healthy vision nor does it improve night vision. In fact, an excess of carrots can cause vitamin A toxicity and carotenemia in rare cases. This misconception arose from an RAF attempt to hide the discovery of radar from the Axis forces by claiming that their pilots had gained vastly improved night vision from being fed carrots, rather than from any technological advancement.

In Korea, it is commonly believed that sleeping in a closed room with an electric fan running can be fatal in the summer. According to the Korean government, "In some cases, a fan turned on too long can cause death from suffocation, hypothermia, or fire from overheating." The Korea Consumer Protection Board issued a consumer safety alert recommending that electric fans be set on timers, direction changed and doors left open. Belief in fan death is common even among knowledgeable medical professionals in Korea. According to Dr. Yeon Dong-su, dean of Kwandong University's medical school, "If it is completely sealed, then in the current of an electric fan, the temperature can drop low enough to cause a person to die of hypothermia."

High levels of testosterone do not necessarily make humans more aggressive and less cooperative, even though this is observed in other animals. Human behaviour is very complicated and heavily affected by social condition and beliefs.

Biology

Warts on human skin are caused by viruses that are unique to humans (Human papillomavirus). Humans cannot catch warts from toads or other animals; the bumps on a toad are not warts.

The claim that a duck's quack does not echo is false, although the echo may be difficult to hear for humans under some circumstances.

The notion that goldfish have a memory of only three seconds is false. They have been trained to navigate mazes and can recognize their owners after an exposure of a few months.

Lemmings do not engage in mass suicidal dives off cliffs when migrating. They will, however, occasionally, and unintentionally fall off cliffs when venturing into unknown territory, with no knowledge of the boundaries of the environment. The misconception is due largely to the Disney film White Wilderness, which shot many of the migration scenes (also staged by using multiple shots of different groups of lemmings) on a large, snow-covered turntable in a studio. Photographers later pushed the lemmings off a cliff.

Bats are not blind. While most bat species do use echolocation to augment their vision, all bats have eyes and are capable of sight.

It's a common myth that an earthworm becomes two worms when cut in half. This is not correct. An earthworm can survive being bisected, but only the front half of the worm (where the mouth is located) can survive, while the other half dies. On the other hand, species of the planaria family of flatworms actually do become two new planaria when bisected or split down the middle.