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Scientists Find Neurological Basis of Risk-Taking Trait

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How do we calculate the right time to take a risk? And why are some people (and dogs, and fish, and rats) bigger daredevils than others? Scientists working with rats say they’ve traced the answers back to a brain region called the nucleus accumbens. They published their findings this week in the journal Nature.

Animals and risk have a curious relationship. Scientists have tested the risk-taking behaviors of many species (including humans), and nearly all of them, when taken as a whole, are more conservative than they need to be. But within each species, there are individual animals who seem to throw care to the wind, and even the most conservative individuals take risks from time to time. 

“Risky behavior has its moments where it’s valuable,” psychiatrist, bioengineer, and study co-author Karl Deisseroth said in a press statement. “As a species, we wouldn’t have come as far as we have without it.”

A little risk-taking is important to keep a species, and an individual, going. But, Deisseroth notes, a predilection for dangerous choices is a liability. “I’ve seen patients whose aberrantly high-risk-seeking activity resulted in accidents, addictions and social, financial or occupational failures that exposed them to a lot of harm and blame.” 

The researchers were looking at the brain’s reward system, which uses hormones like dopamine to motivate us to seek out or avoid objects or experiences, from an angry boss to a cheeseburger. Inside your reward system, and the reward system of other animals, is a structure called the nucleus accumbens (NA). Your NA contains two categories of dopamine receptor cells called DR1 and DR2.

For this experiment, the researchers focused on DR2 cells. They implanted teeny-tiny optical fibers in the brains of lab rats, then taught the rats to gamble. (Fun fact: this is not the first time rats have learned to play the odds.) 

Each rat was set up with a little game center equipped with a hole. When they felt like playing, the rats could poke their noses into the hole, which would trigger the appearance of two levers. Pulling one lever produced sugar water—the same amount every time, no matter what, like a steady paycheck. The other lever was more like a freelance career. Most of the time, pulling lever 2 yielded a little bit of sugar water, but every so often it would pay off with a much bigger helping. The rats could (and did) play the game 200 times a day. 

As expected, about two-thirds of the rats repeatedly went for the dependable sugar water salary. The other third were bred-in-the-bone freelancers. Even after the researchers switched the levers, the rats kept to their preferences. But just like in the real world, some of the conservative rats occasionally went for the risky lever instead. If their risk paid off that first time, they’d keep taking the risk. If it didn’t, they’d go back to their steady sugar paycheck.

While the rats were gambling the day away, the researchers were watching their DR2 cells. They found that just before the conservative rats chose a level, DR2 activity spiked. When the scientists used the optical fibers to light up the risky rats’ DR2 cells, they became more risk-averse, but only as long as the fibers were lit. As soon as the light went off, they went back to their risky behavior. 

Then the researchers gave the rats small doses of pramipexole, a Parkinson’s disease drug that is notorious for causing impulsive gambling in patients. Sure enough, once the drug was in their system, the salaried rats turned to the high-risk freelance life. 

In other words, high DR2 activity in the nucleus accumbens kept conservative rats conservative. “It looks as though we have found a brain signal that, in most individuals, corresponds to a memory of a failed risky choice,” Deisseroth said. “It seems to represent the memory of that recent unfavorable outcome, manifested later at just the right time when it can, and does, modify an upcoming decision.” 

“Humans and rats have similar brain structures involved,” said Karl Deisseroth, MD, PhD, professor of bioengineering and of psychiatry and behavioral sciences. “And we found that a drug known to increase risk preference in people had the same effect on the rats. So every indication is that these findings are relevant to humans.”

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Big Questions
Why Can't Dogs Eat Chocolate?
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Even if you don’t have a dog, you probably know that they can’t eat chocolate; it’s one of the most well-known toxic substances for canines (and felines, for that matter). But just what is it about chocolate that is so toxic to dogs? Why can't dogs eat chocolate when we eat it all the time without incident?

It comes down to theobromine, a chemical in chocolate that humans can metabolize easily, but dogs cannot. “They just can’t break it down as fast as humans and so therefore, when they consume it, it can cause illness,” Mike Topper, president of the American Veterinary Medical Association, tells Mental Floss.

The toxic effects of this slow metabolization can range from a mild upset stomach to seizures, heart failure, and even death. If your dog does eat chocolate, they may get thirsty, have diarrhea, and become hyperactive and shaky. If things get really bad, that hyperactivity could turn into seizures, and they could develop an arrhythmia and have a heart attack.

While cats are even more sensitive to theobromine, they’re less likely to eat chocolate in the first place. They’re much more picky eaters, and some research has found that they can’t taste sweetness. Dogs, on the other hand, are much more likely to sit at your feet with those big, mournful eyes begging for a taste of whatever you're eating, including chocolate. (They've also been known to just swipe it off the counter when you’re not looking.)

If your dog gets a hold of your favorite candy bar, it’s best to get them to the vet within two hours. The theobromine is metabolized slowly, “therefore, if we can get it out of the stomach there will be less there to metabolize,” Topper says. Your vet might be able to induce vomiting and give your dog activated charcoal to block the absorption of the theobromine. Intravenous fluids can also help flush it out of your dog’s system before it becomes lethal.

The toxicity varies based on what kind of chocolate it is (milk chocolate has a lower dose of theobromine than dark chocolate, and baking chocolate has an especially concentrated dose), the size of your dog, and whether or not the dog has preexisting health problems, like kidney or heart issues. While any dog is going to get sick, a small, old, or unhealthy dog won't be able to handle the toxic effects as well as a large, young, healthy dog could. “A Great Dane who eats two Hershey’s kisses may not have the same [reaction] that a miniature Chihuahua that eats four Hershey’s kisses has,” Topper explains. The former might only get diarrhea, while the latter probably needs veterinary attention.

Even if you have a big dog, you shouldn’t just play it by ear, though. PetMD has a handy calculator to see just what risk levels your dog faces if he or she eats chocolate, based on the dog’s size and the amount eaten. But if your dog has already ingested chocolate, petMD shouldn’t be your go-to source. Call your vet's office, where they are already familiar with your dog’s size, age, and condition. They can give you the best advice on how toxic the dose might be and how urgent the situation is.

So if your dog eats chocolate, you’re better off paying a few hundred dollars at the vet to make your dog puke than waiting until it’s too late.

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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Animals
7 Fun Facts for World Elephant Day
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Happy World Elephant Day! Celebrate the occasion with some facts about everyone's favorite gentle giant. 

1. ELEPHANTS CAN RECOGNIZE OTHER ELEPHANT CARCASSES.

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The University of Sussex's Karen McComb told National Geographic that elephants "become excited and agitated if they come across a dead elephant," and, in particular, will investigate skulls and tusks. McComb teamed up with researchers at the Amboseli Elephant Research Project in Kenya to study the behavior, showing wild elephants a range of objects that included skulls. They found that the elephants examined skulls—and tusks in particular—of their own kind twice as long as other skulls, and examined tusks six times as long as they did pieces of wood. They were even able to recognize elephant skulls with the tusks removed, but didn't show preference for certain elephant skulls over others, which suggests they didn't know which skulls belonged to their own relatives. "Animals that are intensely social in life may be most likely to display an interest in their dead," McComb told National Geographic. "But what goes on in their minds while they are doing this is a total mystery."

2. THEY'RE SCARED OF BEES.

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Forget about mice scaring off elephants: When farmers need to keep elephants away from their crops, they should use bees. Researchers in Kenya discovered that even the recorded sound of buzzing bees was enough to make elephants retreat—and cause them to emit low-frequency sound, inaudible to humans, that warns other elephants. "It's impossible to cover Africa in electric fences," Lucy King, author of the paper, told the Huffington Post. "The infrastructure doesn't exist in many places and it would restrict animals' movement." But something like a bee fence—hives strung on strong wires a certain distance apart that would move when elephants walked into them, disturbing the hives—"could be a better way to direct elephants away from farmers' crops," she said.

3. THEY MIGHT UNDERSTAND POINTING.

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Human adults and babies often use pointing as a way to nonverbally get a message across, but not many other animals grasp the concept. But according to a two-month study of 11 tame African elephants, these pachyderms might be able to: When presented with two identical buckets and pointed in the direction of the one containing food, elephants picked up on the cue fairly consistently: Elephants had a success rate of 67.5 percent (1-year-old humans have a success rate of 72.7 percent). But an earlier study of Asian elephants indicated that they don’t notice pointing gestures, which is a bit of a mystery.

4. ONE ELEPHANT CAN "TALK." 

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Koshik, an elephant in a South Korean zoo, developed the ability to imitate the sounds of five words he's heard from his trainer—annyeong (hello), anja (sit down), aniya (no), nuwo (lie down), and joa (good)—by sticking his trunk in his mouth. The scientists who first noticed Koshik’s ability speculate that he learned to “talk” because he was lonely.

5. THEY'RE DIGITIGRADES.

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It's Latin for "finger walking," and what it means is that elephants walk on their toes (there are five of them, as well a sixth false toe). According to the book Mammal Anatomy: An Illustrated Guidemost of the animals' weight "rests on a broad pad of elastic tissue behind the toes" which "acts as a shock absorber and prevents the skeleton from jolting too much when the animals walk. It also allows elephants to move surprisingly quietly despite their size."

6. AN ELEPHANT PREGNANCY LASTS ABOUT TWO YEARS.

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If you thought being pregnant for nine months was bad, be glad you're not an elephant, which can be pregnant for up to 680 days, according to the BBC. All that time in the oven has a benefit, though: Elephant calves are born with highly-developed brains, capable of learning their herds’ complex social structures and ready to put their trunks to use.

7. NINETY-SIX ELEPHANTS ARE KILLED IN AFRICA EVERY DAY.

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Unfortunately, elephant poaching remains a very big problem: An estimated 35,000 elephants are killed annually, their tusks sold illegally in the ivory market. Do the math, and that comes out to nearly 96 elephants every day. Find out what you can do to help elephants and stop poaching at 96Elephants.org.

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