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Why Do We Laugh When We're Tickled?

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It's a mystery that's challenged some of science's greatest minds, including Charles Darwin, Galileo, Francis Bacon, and Plato [PDF]. One thing is for sure: It’s not because we find it funny. In fact, many people find tickling very unpleasant. So why does it make us laugh?

There are two kinds of tickling phenomena: Gargalesis, the heavy tickling that produces laughter, especially by targeting sensitive areas like the armpits and stomach; and knismesis, which is caused by light movement and tends to elicit an itching sensation rather than laughter. You can't tickle yourself because your brain knows it's coming.

When the nerve endings in your epidermis are stimulated by a light touch, they send a signal through the nervous system to your brain. Using functional magnetic resonance imaging machines (fMRI), researchers have determined that two areas of the brain create that tickle sensation: the somatosensory cortex, the area responsible for analyzing touch, and the anterior cingulated cortex, which is involved in creating pleasurable feelings.

Another fMRI study has shown that both laughing at a joke and laughing while being tickled activate an area of the brain called the Rolandic Operculum, which controls facial movements and vocal and emotional reactions. But tickling laughter also activates the hypothalamus, the area of the brain that regulates the fight or flight response—and fires when you’re anticipating pain. This has led some scientists to believe that laughing when you’re tickled could be a natural signal of submission to an aggressor, which would reduce the duration of any attack. It also explains why we may laugh at just the threat of being tickled.

Robert Provine, neuroscientist at the University of Maryland, Baltimore County and author of the 2000 book Laughter: A Scientific Investigation, says that laughter during tickling creates bonds between babies and parents. “When people say they hate being tickled and there’s no reason for it, they forget that it’s one of the first avenues of communication between mothers and babies,” he told Slate. “You have the mother and baby engaged in this kind of primal, neurologically programmed interaction.”

We're not the only animals that laugh when we're tickled: Great apes giggle, and so do rats.

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What’s the Difference Between Prison and Jail?
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Many people use the terms jail and prison interchangeably, and while both terms refer to areas where people are held, there's a substantial difference between the two methods of incarceration. Where a person who is accused of a crime is held, and for how long, is a factor in determining the difference between the two—and whether a person is held in a jail or a prison is largely determined by the severity of the crime they have committed.

A jail (or, for our British friends, a gaol) refers to a small, temporary holding facility—run by local governments and supervised by county sheriff departments—that is designed to detain recently arrested people who have committed a minor offense or misdemeanor. A person can also be held in jail for an extended period of time if the sentence for their offense is less than a year. There are currently 3163 local jail facilities in the United States.

A jail is different from the similarly temporary “lockup”—sort of like “pre-jail”—which is located in local police departments and holds offenders unable to post bail, people arrested for public drunkenness who are kept until they are sober, or, most importantly, offenders waiting to be processed into the jail system.

A prison, on the other hand, is usually a large state- or federal-run facility meant to house people convicted of a serious crime or felony, and whose sentences for those crimes surpass 365 days. A prison could also be called a “penitentiary,” among other names.

To be put in a state prison, a person must be convicted of breaking a state law. To be put in a federal prison, a person must be convicted of breaking federal law. Basic amenities in a prison are more extensive than in a jail because, obviously, an inmate is likely to spend more than a year of his or her life confined inside a prison. As of 2012, there were 4575 operating prisons in the U.S.—the most in the world. The country with the second highest number of operating prisons is Russia, which has just 1029 facilities.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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What Do Morticians Do With the Blood They Take Out of Dead Bodies?
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Zoe-Anne Barcellos:

The blood goes down the sink drain, into the sewer system.

I am not a mortician, but I work for a medical examiner/coroner. During an autopsy, most blood is drained from the decedent. This is not on purpose, but a result of gravity. Later a mortician may or may not embalm, depending on the wishes of the family.

Autopsies are done on a table that has a drain at one end; this drain is placed over a sink—a regular sink, with a garbage disposal in it. The blood and bodily fluids just drain down the table, into the sink, and down the drain. This goes into the sewer, like every other sink and toilet, and (usually) goes to a water treatment plant.

You may be thinking that this is biohazardous waste and needs to be treated differently. [If] we can’t put oil, or chemicals (like formalin) down the drains due to regulations, why is blood not treated similarly? I would assume because it is effectively handled by the water treatment plants. If it wasn’t, I am sure the regulations would be changed.

Now any items that are soiled with blood—those cannot be thrown away in the regular trash. Most clothing worn by the decedent is either retained for evidence or released with the decedent to the funeral home—even if they were bloody.

But any gauze, medical tubing, papers, etc. that have blood or bodily fluids on them must be thrown away into a biohazardous trash. These are lined with bright red trash liners, and these are placed in a specially marked box and taped closed. These boxes are stacked up in the garage until they are picked up by a specialty garbage company. I am not sure, but I am pretty sure they are incinerated.

Additionally anything sharp or pointy—like needles, scalpels, etc.—must go into a rigid “sharps” container. When they are 2/3 full we just toss these into one of the biotrash containers.

The biotrash is treated differently, as, if it went to a landfill, then the blood (and therefore the bloodborne pathogens like Hepatitis and HIV) could be exposed to people or animals. Rain could wash it into untreated water systems.

This post originally appeared on Quora. Click here to view.

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