During a half-hour interval on May 6, 2010, stock prices for some of the largest companies in the world dropped precipitously, some to just pennies a share. Then, just as suddenly and inexplicably, shares recovered to their pre-crash prices.

This unprecedented event, burned into the memories of investors and regulators alike, is now known as the Flash Crash. Since that day, financial markets have seen flash crashes in US Treasury securities, foreign currencies, and exchange-traded funds (ETFs). Other puzzling, system-wide glitches are becoming more frequent as well.

Without a doubt, our financial systems are complex and often unpredictable, and when they swing out of control they remind us how much we still have to learn about how they work and how inadequate our traditional methods of controlling them are.

In all their complexity, though, financial markets don’t hold a candle to the natural world, with its 8 million-plus species – those we know of, not including the millions that have come and gone – interacting and evolving in the world’s forests and oceans and in the microbiomes of our guts.

In the century and a half since Charles Darwin published On the Origin of Species, we still are stymied by the complexity of the biosphere; and, just as with our financial systems, our efforts to intervene have often led to confounding results.

Smokey the Bear offers an example. For seven-plus decades, this popular icon has reminded us of the importance of preventing wildfires. But modern ecological practice recognizes that suppression of all forest fires today simply sets up forests for larger and more destructive catastrophes tomorrow. In all likelihood, financial systems are no different; small catastrophes are probably essential in maintaining their ongoing health.

But how? How might biology inform our efforts to manage markets? How can we get beyond a metaphorical understanding of the ways markets and ecosystems are alike to explore, in practical terms, what our scientific theory offers our financial regulatory apparatus?

Earlier this year, during a Santa Fe Institute-sponsored meeting at the Keck Center of the National Academy of Sciences in Washington, D.C., we pulled together experts from economists to ecologists to evolutionary biologists. We called the meeting “New Approaches to Financial Regulation.” Our intent was to find common theoretical grounds with which to inform future financial regulatory approaches. 

The complex systems perspective

The biosphere and the “financiosphere” are both dazzling in their complexity, with striking similarities. Both are dynamic systems in which the selfish actions of countless individuals – whether they be cells or investors – lead to unpredictable consequences at the system level. In turn, these collective actions and consequences feed back to influence individual actions in endless cycles of adaptation and evolution.

This adaptive cycle is the essence of a complex system. It’s also what makes complex systems difficult to understand, hard to predict, and tricky to manage. 

Not surprisingly, in both the biosphere and financial markets, the resulting system-level emergent phenomena include unexpected crises and collapses, from population crashes to stock devaluations, from the desertification of lush landscapes to market failures, from the disappearance of species to the demise of industries. 

But biological systems also exhibit remarkable resilience. By studying how evolution has made them more robust, might we develop new and wiser approaches to financial regulation? We think so.

Exploration and exploitation

Life began on this planet nearly 4 billion years ago, and despite frequent insults and challenges, we are still here (at least for the moment). We know that life’s remarkable robustness, in large part, is dependent on variation; systems that suppress or lose their diversity are prone to collapse. 

Through continuous innovation, via mutation and sexual recombination, for example, coupled with a seemingly simple filter called natural selection, which leads to the fittest innovations surviving to reproduce, life responds and adapts to changing environments and to itself. Charles Darwin, impressed by the “tangled bank” that emerged from these evolutionary dynamics, revolutionized our understanding of the world about us, and his insights are still with us.

But natural selection’s apparent simplicity turns out to be deceptively complicated. Even the mechanisms of evolution, including those that generate innovation in the form of new variants, are subject to constant modification. Mutation rates (the rapidity at which genetic variants occur) are subject to selection pressures (influences that suppress a population’s reproductive success). Even sexual reproduction itself has evolved to provide a greater variety of genetic material on which natural selection can act.

This interplay between exploration, by which new solutions are tested, and exploitation, by which the best solutions are multiplied and spread, is characteristic not only of evolution via natural selection, but also of the way people, companies, and other institutions must allocate their time and effort to survive and thrive in an economy – which is to say that business and markets are shaped by many of the same evolutionary processes that shape the natural world.

Evolving for the unknown

Importantly, evolution is not about optimization in the abstract; it is about optimization relative to other genetic variants within and across species. While we are evolving, so too are our enemies (like the influenza virus) and our friends (including the microbiomes in our guts). To a large extent, evolution is about preparing for the unknown, because the scope of possible changes in our environments is so immense that we cannot hope to predict their form or timing.

We can predict, however, that during our lives, we will be assaulted by a variety of pathogens. Thus, vertebrates have evolved a contingency plan in the form of immune systems and barriers to invasion, such as skin and cell walls. These systems combine early warning indicators and generalized first lines of defense that buy time while we populate our immune repertoire with more specialized antibodies tuned to the specific threats. This is akin to circuit breakers in financial securities markets, which shut down trading when volatility is too high.

At the same time, mammals have evolved regulatory systems that help maintain the stability of our systems. Human heart rate and breathing, for example, are regulated by physiological processes that correct deviations from the norm in the time scales required for survival – kicking them into overdrive when we’re being chased by a tiger, for example. 

But when our physiological feedback loops are too weak or too slow, or too strong, pathologies arise.

Regulatory feedbacks that are “just right” help maintain a healthy human.

Similarly, when the time scale of financial innovation outstrips that of regulation – as in the case of high-frequency trading – there are likely to be unintended consequences. But regulatory responses that are too strong or poorly timed – like emergency price controls, short sales restrictions, bank holidays, and extreme capital constraints – can lead to greater panic and uncertainty among investors and consumers, ultimately causing even less desirable outcomes such as housing market crashes, rapid inflation, and recessions.

Regulatory feedbacks that are “just right” help maintain a healthy economy.

Self-organized robustness

These complex interrelationships underscore the importance of maintaining diversity in financial markets, in part by allowing enough exploration (that is, financial innovation) to produce the requisite diversity for a healthy system. But what is the right amount?

As mentioned earlier, evolution has dealt with the diversity problem in part by regulating evolutionary processes themselves: the rate at which mutations occur, and sexual recombination, which helps ensure a reassortment of the genes in a population and the production of new variants.

We tend to think of evolutionary change primarily in terms of natural selection based on the reproductive success of individuals with helpful traits. But all complex systems, including biological systems and business ecosystems, also exhibit self-organized patterns at scales larger than at the level of individuals. Such self-organization also “selects” by producing, from the interactions of individuals, emergent features that themselves either persist or wane. The self-organized systems that persist, and that we observe, tend to have properties that make them more robust. 

Such self-organization does not always lead to robust systems, however; self-organized phenomena may also contain the seeds of system collapse, as we saw in the financial crisis of 2008–2009, when financial innovation and unprecedented connectedness, among other factors, combined to bring the system to the brink of failure. 

Still, some features of biological systems might be helpful in designing self-organized financial systems for robustness.

Redundancy provides insurance against loss. The American chestnut largely disappeared from the forests of the Northeastern United States, but other species filled its niche. In 2004, though, when Chiron, one of only two companies providing flu vaccines in the US, announced that its plants in Liverpool were contaminated, our house of cards was at real risk of collapse. We were too dependent on too few suppliers.

Modularity (the inverse of connectedness) isolates related elements, limiting systemic risk by reducing the potential for a local problem to spread globally. Quarantines and barriers restrict movement of infected individuals to help control the spread of a contagion. Such methods are used not only for human diseases, but for livestock, as in the case of foot and mouth disease. Likewise, modularity in financial systems can help keep problems that emerge in one market or industry from spreading to others and pulling the whole system down.

In biology, breakdowns in size regulation, such as with gigantism, are considered unhealthy for biological organisms. Likewise, the unchecked growth of financial institutions can lead to banks that are “too big to fail,” which, we now understand clearly, can threaten global financial stability.

Cues from evolution

Any view of financial systems must recognize that they are ecosystems, linking agents, stocks, and flows. Just as an ecosystem ecologist is focused on the cycling of crucial elements like carbon, nitrogen, and phosphorus, so too might a “financial ecologist” focus on the sustainable cycling of crucial elements like capital, labor, and financial innovation. 

As we refine and define the levers by which we attempt to manage tomorrow’s economies, we must keep in mind that regulations that focus on specific parts of systems often miss the big picture. In the build-up to the 2008 crisis, for example, bank regulators naturally focused on the banking industry, neglecting the impact of the rapidly emerging shadow-banking system and its impact on financial stability.

Management of ecological systems in the past has often opted for narrowly derived or simplistic interventions, but the ensuing failures have led to calls for ecosystem approaches – in the management of fisheries and forests, for example. Similarly, our failures to predict and control financial ecologies should remind us that, if anything, the interconnectedness of global financial systems is ever greater, and a holistic approach is essential if we are to succeed.

As adaptive complex systems, natural and financial systems share deep likenesses. We should take cues from billions of years of evolution. Nature, and biology, offer solutions to a number of challenges of financial regulation, not to mention the regulation and control of many other systems crucial to well-functioning societies.

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NOW WATCH: The biggest mistake people make when brushing their teeth

After being stung by a wasp or two, most of us learn that we'd rather avoid creatures that can cause us a good amount of pain simply by plunging a spike on their abdomen into our skin.

Not Justin Schmidt.

Schmidt is an entomologist who studies stinging insects. He is known for creating the Schmidt sting pain index, which goes from a one (like a sweat bee) to a four (a tarantula hawk wasp). The yellow jackets that were likely the first stings many of us experienced are a two.

The index, which Schmidt developed after getting stung by insects of all stripes throughout his career, measures just how bad each and every one of those stings really are.

So how bad are the worst of the bunch?

In a recent video for Great Big Story, Schmidt gets down to details:

Of the bullet ant (a four-plus), Schmidt says: "Pure, intense, brilliant pain ... Like walking over flaming charcoal with a three-inch nail embedded in your heel."

As you can tell from the name, other people describe it as similar to the sensation of being shot.

Ouch.

And that's just one of the many stings Schmidt rates in his new book, "The Sting of the Wild."

For him, it's not some sort of masochism — he is fascinated by stinging insects, and sometimes those painful pricks are just part of the job.

"Yeah, I get stung, but that's all just part of the passion, that gives me data," he said. "A sting helps me in understanding what the insect is doing."

At least someone out there is figuring out these details so we don't have to.

SEE ALSO: Guess which body part hurts the most when stung by a bee

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Today, on August 25, 2016, the U.S. National Park Service is celebrating its 100th birthday.

From the founding of the first park — Yellowstone— to today, the park service has protected and preserved large swaths of wilderness, from shorelines to mountain ranges, as well as myriad of historic sites and monuments. And today, the park system expands across 84 million acres, covering 412 sites.  

Over the last century, these parks are, and have always been, vital to science by providing living laboratories for research in some of the most intact natural landscapes in the world. In addition, because these natural sites have been managed and studied for nearly a century, there is a huge wealth of archival scientific data available to researchers working in the parks today.

To find out more about the role that national parks have played in the history of science, Business Insider spoke to Timothy Watkins, a climate change science and education coordinator at the National Park Service who is working with the US Geological Survey to draw attention to the scientific value of parks. Here are just a few national sites that have been instrumental.

Simone Scully contributed to this post.

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Yellowstone National Park

Renown for being America’s first National Park, Yellowstone is also the site where microbiologist Thomas Brock discovered an interesting bacterium living in the park’s hot springs. This bacterium, which Brock named Thermus aquaticus, was able to survive in waters that were 80 degree Celsius (176 degrees Fahrenheit).

“That was just absolutely astonishing because nobody thought that anything could live at that temperature,” Watkins told Business Insider. “It revolutionized our understanding of the way life had evolved [to] survive in extreme environments.”

After Brock made his discovery, other scientists studying this bacteria found that it is an important, stable source of the enzyme DNA polymerase, which allows DNA strands to replicate. “They realized that you could use that thermally stable DNA polymerase to do some very important engineering and chemistry in the lab,” Watkins said, and researchers, who later won the Nobel Prize in 1983, developed a technique using this enzyme, called the polymerase chain reaction (PCR), which is used in medical and biological research to amplify copies of a segment of DNA.

“But it all started with a bacterium that was found in Yellowstone National Park,” Watkins said.

Isle Royale National Park

Isolated in the middle of Lake Superior, Isle Royale National Park is a rugged, small island, and it was also here that, in 1958, wildlife biologist Durward Allen began doing some some incredibly important research on the predator-prey relationship of wolves and moose. This project has continued ever since, with scientists returning every year to count the populations of these two animals, and today, this research project is the longest continuous study of any predator-prey system in the world.

“It’s really important field ecological data on real live populations out in the wild that has produced a data set that is just incomparable,” Watkins said. “[It] has informed and confirmed certain models of populations of predators and prey relationships in ecology that were derived from mathematical models or studies of bacteria or very small organisms in the lab … and a lot has been learnt from the predator-prey relationships, as well as the influence of disease and climate change.”

Durward Allen is largely considered a pioneer among ecologists for initiating the Isle Royale wolf-moose project and having the insight to understand the value of continuing to observe a site long after others would have moved on to study something different. “That work really became canonized and is in every introductory textbook on the market now,” Watkins added.

Tule Springs Fossil Beds National Monument

Located just north of Las Vegas, Nevada, Tule Springs Fossil Beds National Monument is the site where nuclear physicist Willard Libby field-tested his technique of Carbon-14 dating.

Libby, who had been a part of the Manhattan Project, developed this technique of Carbon-14 dating, also called radiocarbon dating, after World War II. Carbon-14 is an isotope of carbon that decays naturally, so Libby realized that it is possible to measure its concentration in an object and compare it to other isotopes of carbon in order to calculate the object’s age.

He had developed the method of carbon-14 dating in the lab and tested it on some museum specimens, but the first time Libby actually used the technique in the field was on Pleistocene-era mammal fossils in Tule Springs, and his results showed that these mammal fossils were 30,000 years older than any human presence in the area.

“He provided evidence that falsified the hypothesis that humans were killing and cooking those mammals,” Watkins explained.

Libby’s work on Carbon-14 dating won him the Nobel Prize in 1960, and today the site of his research is protected by the National Park Service as a national monument.

Early in his career, Justin Schmidt realized he had a problem.

Schmidt, a budding entomologist, and his zoologist wife had just returned to the University of Georgia from a trip around the country.

They'd been collecting different species of harvester ants, "nasty stinging insects whose venom chemistry was unknown," as he describes them in his fascinating new book, "The Sting of the Wild."

To learn the details of the venom for his dissertation, they had to analyze incredibly large numbers of the creatures, which meant getting up close and personal with them.

Debbie, Schmidt's wife, describes her first harvester sting in the book as a "deep ripping and tearing pain, as if someone were reaching below the skin and ripping muscles and tendons; except the ripping continued with each crescendo of pain."

After collecting buckets of the creatures, the plan was to analyze them and compare the venoms from different specimens. To assess venom, Schmidt needed to evaluate both toxicity and pain. Toxicity was straightforward — already existing measures could be used. But there was no existing scale to measure the pain of insect stings.

Thus was born the "Schmidt Pain Scale for Stinging Insects." It was a four-point system, anchored by the well-known sting of a honey bee (rating a two), something people all over the world could be familiar with. To go up or down a full point, a sting had to be discernably more or less painful than the stings on another level. Half points could be used for pricks that fell somewhere between levels.

Over the years, Schmidt added new species to the list. He mostly didn't try to get stung. It just happened, more than 1,000 times, from at least 83 different species that have been evaluated on the index.

We've picked out insects that will illustrate the full scope of the scale, including a few that demonstrate the worst of the worst:

SEE ALSO: A man who has been stung more than 1,000 times reveals the one bug you really want to avoid

Red fire ant

Scientific name: Solenopsis invicta

Range: Native to South America

Description: "Sharp, sudden, mildly alarming. Like walking across a shag carpet and reaching for the light switch."

Pain level: 1

Western cicada killer

Scientific name: Sphecius grandis

Range: North America

Description: "Pain at first sight. Like poison oak, the more your rub, the worse it gets."

Pain level: 1.5

Western honey bee

Scientific name: Apis mellifera

Range: Native to Africa and Europe

Description: "Burning, corrosive, but you can handle it. A flaming match head lands on your arm and is quenched first with lye and then sulfuric acid."

Pain level: 2

There are few places in the world where it's possible to find a baby great white shark.

We've known that nurseries for these mysterious and far-swimming creatures can be found off the coasts of South Africa, eastern Australia, and Southern California. Now, it looks like we can add a new location to the mix.

A team of researchers just tagged nine baby white sharks right off the coast of Long Island, which likely confirms that there's another nursery just outside of New York City.

The remarkable finding was the result of an expedition that included scientists from shark research group Ocearch, the Wildlife Conservation Society, NOAA Fisheries, and several other institutions.

They had reason to think there might be a nursery in the region.

"Researchers and fishermen have been sporadically reporting the presence of small white sharks from the waters off Long Island for many decades," Tobey Curtis, a shark scientist with NOAA Fisheries, tells Business Insider via email. "It’s the only place on the coast with such a high concentration of baby white shark observations. But this was the first real focused research effort to tag them."

"This Long Island site is very special, and it’s amazing to me that these sharks appear to be thriving in the shadows of one of the biggest cities in the world," he says.

If the sharks spend a lot of time in the area, which seems likely as it's the only North Atlantic spot where so many newborn white sharks have been found, then this is likely the nursery habitat for the sharks. Curtis says it's likely the pups are born close by as well.

Curtis's research was one of the main factors that led the team to believe there might be a nursery in the Long Island area. As he told WNYC, he'd scoured records from the past 200 years and found that almost all the baby great whites seen in the North Atlantic in the past 200 years were spotted right off the Long Island coast, where there's a contentinental shelf, shallow water, and plenty of food.

Ocearch's GPS tagging system helps researchers (or anyone interested!) follow the sharks after they've been tagged. As you can see on their site, many of the newly tagged pups are still right in the area, swimming up and down the coast. This is probably a good point to mention that these baby sharks are not a threat to humans — they're too small for that, and most people really have nothing to fear from sharks.

In May, a rather-famous adult female white shark named Mary Lee that Ocearch had previously tagged returned to the New York area, which was another indicator that the region was a promising nursery site.

Now that the new juveniles have been tagged, the fascinating thing will be to watch what they do next. Curtis tells Business Insider that they expect that the pups will leave after temperatures drop this fall — the curious thing will be to see if they come back next summer.

"I think the most noteworthy findings are yet to come, as we follow the tracks of these white sharks over the next several years," he says. "These are the first baby white sharks to be tagged in the North Atlantic and we have no idea what to expect."

SEE ALSO: Microsoft billionaire Paul Allen is on a mission to save the world’s sharks, and he’s found some lurking in unexpected places

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Not all giraffes are the same species, it turns out. 

Based on a new study published Thursday in the journal Current Biology, researchers concluded that giraffes belong to four species, rather than just the single previously recognized one (Giraffa camelopardalis):

• Southern giraffe (G. giraffa)
• Masai giraffe (G. tippelskirchi)
• Reticulated giraffe (G. reticulata)
• Northern giraffe (G. camelopardalis)

For the study, the researchers looked at 190 giraffes in Africa. Based on their genes, the researchers concluded that the giraffes likely became separate species somewhere between 1.25 and 2 million years ago. 

Apart from their genetic differences, the researchers also noted distinct physical traits among the animals. For example, as The New York Times notes, Masai giraffes have darker spots and more jagged lines on their skin, while northern giraffes tend to have horn structures.

The news does also has some unintended consequences for zookeepers: 

“All zoos across the world that have giraffes will have to change their labels,” Axel Jenke, a geneticist at the Senckenberg Biodiversity and Climate Research Centre and one of the authors of the study told The Times.

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For the first time, researchers have recorded two Black Sea bottlenose dolphins having a 'conversation' with each other, and their communication appears to be far more sophisticated than we thought.

While scientists have known for years that dolphins use a very complex language to communicate amongst themselves, the new findings suggest that they might be able to string together five-word sentences, and could even use a form of 'grammar' to influence meaning.

"Essentially, this exchange resembles a conversation between two people," team leader Vyacheslav Ryabov, from the Karadag Nature Reserve in Feodosiya, Russia, told Sarah Knapton at The Telegraph.

"Each pulse that is produced by dolphins is different from another by its appearance in the time domain and by the set of spectral components in the frequency domain."

The team discovered these speech patterns using a new type of waterproof microphone called a hydrophone. This allowed them to record two dolphins at the reserve - named Yasha and Yana - with a high level of detail.

After analysing these recordings, the team says they've found evidence that the dolphins were forming 'words', by emitting different pulses that varied in frequency, volume level, and spectrum, just like human language.

While it's impossible to know at this stage what these words could mean, the team says the dolphins appeared to be forming sentences up to five words in length during their brief conversation.

There's even evidence of grammatical structures in place too, which would allow for more complex sentences, but more evidence is needed to confirm this.

What's perhaps most fascinating about the interaction is that the dolphins appeared to be keenly interested in what the other had to say, and understood that they had to take turns vocalising to get their meaning across.

"The analysis of numerous pulses registered in our experiments showed that the dolphins took turns in producing [sentences], and did not interrupt each other, which gives reason to believe that each of the dolphins listened to the other's pulses before producing its own,"Ryabov told The Telegraph.

"This language exhibits all the design features present in the human spoken language, this indicates a high level of intelligence and consciousness in dolphins, and their language can be ostensibly considered a highly developed spoken language, akin to the human language."

Based on these findings, Ryabov says there's enough evidence to suggest that dolphins do, indeed, have their very own language that we're only just beginning to understand.

The next step - and it's a big one - will be to figure out how to translate their 'words' into a human language.

"Humans must take the first step to establish relationships with the first intelligent inhabitants of the planet Earth by creating devices capable of overcoming the barriers that stand in the way of using languages and in the way of communications between dolphins and people,"Ryabov said.

Speech might not be the only thing humans and dolphins have in common. Back in 2011, researchers found that dolphins value friendships and close relatives just like we do.

And earlier this year, scientists from Italy found that dolphins (and whales) mourn their dead.

It's going to take a whole lot more research to get us to a place where we can understand much of anything that dolphins are saying to each other, but being able to identity the key constituents of their speech patterns is a pretty great jumping-off point.

The findings were published in Physics and Mathematics.

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The brain, with its 100 billion neurons, allows us to do amazing things like learn multiple languages, or build things that send people into outer space. Yet despite this astonishing capacity, we routinely can't remember where we put our keys, we forget why we went to the grocery store, and we fail when trying to recall personal life events.

This apparent contradiction in functionality opens up the question of why we forget some things but remember others. Or, more fundamentally, what causes forgetting?

This week my book 'The Memory Illusion' drops in Canada, and as a Canadian girl I want to celebrate this by showcasing some Canadian researchers who have given us insight into precisely this question.

An article published recently in Psychological Science by Talya Sadeh and colleagues at the Rotman Research institute in Toronto addresses a long-running debate in the world of memory science; do we forget things because of decay or interference?

A message in the sand

Decay. Advocates of the decay account posit that our memories slowly disappear, fading because of a passage of time during which they have not been accessed.

You can picture this much like a message written in sand, with every ocean wave that flows over the shore making the writing less legible until it eventually disappears entirely. The sand represents the web of brain cells that form a memory in the brain, and the ocean waves represent time passing.

Interference. Often contrasted with this is the interference account, where it is thought that "memories are made less accessible because of interference from similar information acquired before or after their formation", according to Sadeh and colleagues.

In our beach example, this means that instead of waves slowly corroding the message, a child comes along and writes over it. This makes the message making harder, or even impossible, to read. The child in this example represents a new experience, and the message it writes is the information left behind in the brain by that experience. This leads to forgetting because it essentially overwrites the original memory. This is a process that can also lead to false memories, my favorite topic.

Representation theory

What Sadeh and her Canadian colleagues help to illustrate is that these theories need not stand in competition with one another. Both decay and interference are important for understanding forgetting.

According to their paper, which makes a case for the 'representation theory of forgetting', "the primary cause of forgetting… depends on the nature of the initial memory." The researchers found support for their theory of forgetting by conducting a word memory experiment with 272 students from the University of Toronto. Here, participants were randomly assigned to experimental conditions that varied in terms of how long they waited between learning words and having to remember them, and the extent to which their memory of the words was interfered with by the things they had to do between learning and remembering.

According to the authors, they found support for the idea that a memory can take the form of two different representations in the brain; familiarity or recollection.

'Familiarity' is a memory process that allows us to remember something, but without specific details. It is the idea that we 'know' something happened although we cannot remember the original context. This is like when you feel you recognize a face, that guy looks so familiar, but you cannot put your finger on where you know the person from.

In contrast to this, if you have a 'recollection' of something, you also remember the context of the memory. In this process you recognize that guy, and you remember his name or other defining details. That's Ed.

Blame the hippocampus

Our Canadian research team suggests that these two types of memory representations act differently, and look different in the brain. Each of them is thought to rely differently on a key part of the brain, called the hippocampus, which is important for making memories; "Recollection-based memories, supported by the hippocampus, are… relatively resistant to interference from one another. Decay should be a major source of their forgetting. By contrast, familiarity-based memories, supported by extrahippocampal structures… [are] sensitive to interference."

Combining our metaphors, that guy who looks so familiar is information that is likely to be forgotten because the child writes over it in the sand, while recalling that's Ed is more likely to disappear due to waves washing the memory away over time.

So, what have we learned? Why we forget seems to depend on how a memory is stored in the brain. Things we recollect are prone to interference. Things that feel familiar decay over time. The combination of both forgetting processes means that any message is unlikely to ever remain exactly the way you wrote it.

The views expressed are those of the author(s) and are not necessarily those of Scientific American.

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The key difference between human beings and Neanderthals is how we consume and expend energy. It goes a long way toward explaining why we survived to the modern era while our — literal— kissing cousins died out.

That's one of the interesting takeaways from a long article by Vox's Brain Resnick exploring the inter-species sex lives of Homo sapiens and Homoneanderthalensis.

(Every living person not of exclusively African descent has some Neanderthal ancestry. It appears Neanderthals never made it to Africa.)

Resnick spoke to Bernard Wood, a paleoanthropologist at George Washington University. Here's the bit of their conversation that stuck out to me:

"They probably needed about another 600 or 700 calories a day more than a modern human" to feed their hardier bodies, [Wood] explains — great in times of plenty but catastrophic in a famine. They were the gas-guzzling pickup truck of the hominids. We were the smart car.

That goes a ways toward explaining why our species of human out-competed Neanderthals, even as we mated with them.

It's unclear how smart or social Neanderthals were, but we know they never formed the kinds of large, aggressive bands that Homo sapiens did. They were squatter than us, and bulkier, with wide bones and short foreheads. We also know their numbers dwindled, and then they disappeared around 40,000 years ago.

Wood's suggestion, that Neanderthals were simply not energy-efficient enough to survive periods of scarcity, is compelling. (Still, as he points out later, Neanderthals managed to survive for a million years, far longer than we have so far.)

To be clear: Wood doesn't claim that this difference in caloric need is the complete explanation for Neanderthals' demise, but he does conjure an intriguing image — a species that simply requires more resources than the world could always offer.

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When we talk about smart animals, we tend to give credit to a few creatures: chatty dolphins, long-remembering elephants, tool-using apes, and puzzle-solving crows, to name a few.

But do we really understand just how smart, how able to communicate thoughts and even, dare we say it, feelings, some animals are?

Most of us don't give them enough credit, according to a September 13 talk at Cooper Union by ecologist Carl Safina, author of "Beyond Words: What Animals Think and Feel."

Take elephants, for example.

African elephants in Amboseli National Park in Kenya can distinguish the language and voice of Maasai warriors from the language and voices of farming tribes that live in the same region, Safina explained.

University of Sussex researchers Karen McComb and Graeme Shannon published a study in 2014 documenting this remarkable ability.

Maasai tribesmen will occasionally attack and kill elephants with their spears, Safina explained. Elephants know that they're dangerous.

Even before McComb and Shannon published their work, researchers knew that elephants would turn defensive, ready to fight, if they saw the red clothes worn by the warriors. They'd prepare to flee if they smelled the Maasai attire. But the giant creatures are basically untroubled if they smell or see clothing worn by farmers of the Kamba tribe, another group in the region.

McComb and Shannon showed that elephants could also tell the difference between the Ma language of the Maasai and the language spoken by the Kamba.

"They have very clear behavioral responses in all of these situations," McComb told Virginia Morell of National Geographic when the study was first published.

So McComb and Shannon decided to see how elephants respond to language. They recorded men, women, and children from the Maasai groups and Kamba groups saying a simple phrase in their own tongue: "Look, look over there, a group of elephants is coming."

The elephants ignored the voices of Maasai women and children, even if the children were male. They ignored the voices of Kamba men. But when they heard the Maasai men speaking in their language, they prepared to flee.

"They understand that there are different kinds of people," Safina explained in his talk. (That's more than we can say about most people's perception of elephants.)

"The elephants' decision-making is very precise," McComb told Morell, "and it illustrates how they've adapted where they can to coexist with us. They'd rather run away than tangle with a human predator."

And as Safina points out, this group decision, this shared fear, is a sort of empathy.

Empathy, as he describes it, is "the ability of a mind to match the mood of companions." And in the case of this recognition that someone dangerous is coming and it's time to go, it fits the behavior of the elephant.

"If everyone around you hurries up, you've gotta hurry up," Safina said.

Unfortunately, these behavioral adaptations aren't quite able to keep up with human firepower. They can't keep away from poachers firing automatic weapons from helicopters.

"In Roman times, elephants were found from the shores of the Mediterranean to the Cape of Good Hope," with the exception of the harshest parts of the Sahara, said Safina. Now, these intelligent, communicative creatures "are being driven extinct so we can carve their teeth."

SEE ALSO: 10 survival myths that might get you killed

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NOW WATCH: Watch as this baby elephant is helped out of a well by local villagers

When my wife became pregnant with our first child, we could barely contain our joy.

Then we panicked.

To vanquish our ignorance, we both started reading immediately and obsessively on the latest science behind pregnancy and child development.

A few surprising facts stood out in that torrent of books, studies, articles, and apps.

But the ones I found the most eyebrow-raising had to do with the awareness possessed by babies in the womb: Their hearing and sight develops remarkably early and begins sponging up information far sooner than I expected.

When and what can babies hear?

Every baby, mom, and pregnancy are different, but most of a fetus' inner ear structures form by week 16, allowing it to hear sound.

By 24 weeks, the cochlea, eardrum, ossicles, and other crucial ear structures are fully formed — and the "record" light is on in the baby studio.

From then on developing babies can easily hear mom's heartbeat, eating, breathing, walking, talking, exercising, burping, and digestive gurgling.

This may help explain why babies find noise so comforting. There's also some evidence to suggest babies learn to recognize and react to mom's voice while inside the womb.

Do loud sounds hurt unborn babies?

The sounds a mom exposes herself to are what a baby is exposed to as well, but babies can't put in ear plugs.

The CDC says moms should avoid very loud noises exceeding 115 dBA— chainsaws, gunfire, jet engines, blaring music, loud concerts, and so forth.

Consistent loud noise (like heavy machinery) can also damage a baby's hearing in the womb.

What about loud but non-damaging sounds? Those can surprise babies in the womb, sometimes enough to even make them cry.

When and what can babies see in utero?

Although a baby's eyes can "see" light starting around week 16, their peepers aren't recognizable (as we know them) until about week 20.

The eyes first open between weeks 26 and 28, doing so most regularly starting around 32 weeks into a pregnancy. Development of vision is tremendously complicated, so a lot of it continues after birth.

And yet, a fetus can see inside the womb. Their vision is rather blurry, but they sometimes respond (with a flutter of activity) to bright sources of light like the sun or a flashlight pointed at a woman's belly.

Getting outside often might even help a baby's eyes develop and reduce the risk of a few eye disorders.

What does it look like inside there?

Imagine being inside a big, thick, red balloon that's filled with water. A flashlight projecting through your cheek to create a dull red glow is probably a good (and more practical) example.

SEE ALSO: Babies cry in the womb and 18 other surprising facts I learned when I became a dad

DON'T MISS: Here's why '9 months of pregnancy' is a myth

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NOW WATCH: Scientists figured out what diseases you’re more likely to get based on your birth month

Helen Fisher, biological anthropologist and author of "Anatomy of Love," says heartbreak has physiological effects on our minds and bodies. There's a scientific reason it hurts so much.

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It's estimated that Influenza — the common flu — was the cause of death in 30 to 50 million people in 1918 and 1919. It was the second deadliest pandemic in history, just behind the Black Plague.

We brought in Dr. Stephen Morse, Professor of Epidemiology at Columbia University, to talk about how it happened — and why we're all still at risk. 

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If you live in a big city like New York, you're probably familiar — a little too familiar, perhaps — with bed bugs.

As their name suggests, they start by infesting the places we sleep.

Within weeks, the blood-sucking creatures have turned an entire apartment into an itchy nightmare.

And their numbers are on the rise.

Since the early 2000s, bed-bug infestations have grown more common in the US, UK, Canada, and Europe, according to the US Centers for Disease Control and Prevention.

Part of the reason? They've evolved resistance to our defenses against them. The bed bugs of today, for example, have thicker, waxier exoskeletons (to shield them from insecticides) and faster metabolisms (to beef-up their natural chemical defenses).

They're also being transported with increasing frequency by people traveling internationally, according to the British health agency NHS. As they follow us across the globe, the pests get tougher. "In a way, we created the modern bed bug: it evolved to live on us and to follow us," science writer Brooke Borel explained in her recent book, "Infested."

From cave to city

Bed bugs didn't always used to be the terrifying critters we know today. For decades, we lived in peace, undisturbed by these tiny creatures of the night. Our cave-dwelling ancestors, in fact, got along perfectly fine with bed bugs. Back then, biologically speaking, they were practically a different species.

Yet as humans migrated out of caves and into cities over thousands of years, we brought bed bugs along for the ride. Not surprisingly natural selection began to influence their characteristics: The critters with traits that made them better able to survive in their new digs outlived their peers who weren't as well suited for the urban lifestyle. These new bugs were more active at night, when humans sleep, and had longer, thinner legs for hopping away from us quickly.

Bed bugs are still evolving

Scientists still aren't entirely sure why bed bugs have started to come back so strongly in the past decade, Borel writes, but what we do know is that people are playing an important role in their recent return.

It all began shortly after World War II, when scientists created the powerful insecticide DDT. We managed to temporarily wipe out tons of insects, including bed bugs, writes Borel. But all the while, their resistance to insecticides grew. Then, as international travel got more common, bed bugs hitched a ride on everything from travelers' shoes to their luggage, spreading across the globe.

How to spot a bed bug

Adult bed bugs are flat, oval-shaped, and visible to the naked eye, according to the NHS. Their color can range from dark orange to red or brown.

Female bed bugs can lay up to 300 eggs over the course of their lifetime. The eggs stick to surfaces and hatch after about 10 days. Baby bed bugs grow into adults in roughly six to eight weeks, all the while shedding their skin. If you have a bed-bug infestation, you can typically spot these shells, which appear wrinkly and light brown, on your bedding.

Bed bugs aren't limited to hotels or hostels and can be found in all types of housing, the NHS reports.

If you think you have a bed-bug infestation, the NHS recommends getting in touch with your local pest-control company.

SEE ALSO: This scientist had a bed bug breakthrough after subjecting herself to 180,000 bites

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NOW WATCH: This is what happens to your brain and body when you check your phone before bed

Humans may have a bad reputation for being warmongering and violent, but when it comes to killing each other, meerkats actually have us beat.

According to new research from Spain's Higher Council for Scientific Research (CSIC), nearly one in five meerkats die at the hands (or paws) of their own. Contrary to their cute looks, meerkats and some other small animals murder each other more often than supposedly aggressive animals like wolves, brown bears, and humans.

In other words, the study found, people are pretty violent, but in the grand scheme of things we're actually just on par with our relatives. 

"The biggest surprise was to realize how widespread is lethal violence among mammals," Dr José María Gómez, a professor of ecology at the University of Grenada who led the study, told Business Insider. "It was also striking that lethal violence was not concentrated in the groups that we tend to consider 'violent', such as carnivores." 

Still, primates stand out for their violence compared with other animals.

The team found that primates — the group that contains humans, apes, monkeys, and lemurs — were particularly violent as a group, with the number of deaths being caused by a member of the same species at 2.3%. Apart from meerkats, the other four out of the top five spots belonged to primates — ranging from a whopping 16 to 19%.

The current statistic for humans killing each other is only slightly lower than the primate average at 2%, but this was higher in some prehistoric times, particularly during periods with many wars.

For example, during the Paleolithic era— the early stone age — lethal violence was around 3.5%, and this rose to 12% during the Medieval times, which included the Battle of Hastings in 1066. That's more than 1 in every 10 people being murdered by someone else. Gómez says we humans probably developed a habit for being so violent because we are both social and territorial creatures.

"Mammals, territorial and social species showed significantly higher values of lethal violence than solitary and non-territorial mammals," he said. "Sociability probably involves more opportunities to conflict than solitary habits."

In other words, being sociable provides more incentives and chances for killing each other.

Why do individuals in evolving societies still kill each other? 

The team looked at many types of lethal violence including infanticide, cannibalism and deaths resulting from male-male fights. Each has a particular set of causes and circumstances, and Gómez explained that as long as conditions exist where some of these kinds of violence provides some benefits, deaths will continue to happen.

The study didn’t explore why lethal violence occurs in societies that are supposedly evolving, but Gómez could speculate.

"Violence is sometimes an unintended result of some interactions between individuals. As long as conflicts exist, some lethal death is expected to occur eventually even if no one gets any profit out of it," he said. "We would say that lethal violence is a potential result of conflict solving... whether we can articulate ways to solve conflicts without lethal violence is an open question, but our study suggests that, to some extent, that can be done."

The team are now exploring whether different types of lethal violence, like infanticide, aggression or cannibalism, may have evolved from different patterns. This could help differentiate between why some methods are more common in some species. It could also start to help explain why animals can be so murderous when on the surface they appear to be cute and cooperative, such as meerkats.

SEE ALSO: A group of anthropologists says it finally knows how iconic early human ancestor Lucy died — and other researchers are livid

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NOW WATCH: Scientists discovered something 'shocking' that could rewrite a key part of human evolution

You know that after pushing yourself hard your body is going to be sore.

That might be middle-of-the-road, pretty-good sore if you've just played an unexpectedly intense game of pick-up soccer, or it might be holy-hell, what did I do to myself sore if you've just raced a triathlon or decided to open the winter season with a day snowboarding on steep trails.

Either way, you might be inclined to reach for an over-the-counter pain reliever like ibuprofen (Advil) when you are done. It seems like it makes sense. You've shredded your muscles and stressed your ligaments, bones, and tendons, and you know there's some inflammation there. So why not take an anti-inflammatory drug?

But for general soreness — especially if you want your body to recover best and get stronger — you shouldn't.

Inflammation causes pain, but it's also the first step towards healing. When you work out you're damaging muscles. In response your body adapts, healing that damage and making you stronger so that you can better handle those forces in the future.

Some research has found that some of the pro-inflammatory compounds produced by exercise then cause the release of powerful anti-inflammatory substances that help damaged muscles heal and have other long-lasting health benefits. There's reason to think that artificially suppressing the initial inflammation could prevent that healing process, neutralizing some of the real benefits of exercise.

Studies in mice have shown that ibuprofen cancels out some of the skeletal muscle growth that would normally happen after distance running. And while mice aren't people, human research seems to agree. Some researchers have found that both ibuprofen and acetaminophen (another type of pain reliever, often branded as Tylenol) suppress the protein formation that occurs in muscles after high-intensity exercise. Even more research has found that nonsteroidal anti-inflammatory drugs like ibuprofen (aspirin is also in this category) inhibit bone healing. There's even some evidence showing that using ibuprofen regularly for soreness may damage cellular tissue and generally prevent your body from even being able to take full advantage of exercise.

Even using ice baths or ice packs to reduce inflammation can slow the body's adaptation process, though that just delays healing, it doesn't actually stop it from happening.

There's an exception to all this, of course. If you have an actual injury, using a painkiller to reduce inflammation may help you heal.

But for general muscle soreness, you're better off just toughing it out.

SEE ALSO: The 2 exercises that will keep you fit for life

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NOW WATCH: Turns out LA’s shade balls actually worked

While every STAT story aims to stimulate your cortex, if this one falls short and makes you yawn, you can thank us anyway — at least if a study published Tuesday is right.

If you have a big brain, you can credit yawning for promoting brain growth and activity, the researchers found. And if you have a small brain, you can blame the fact that you don’t yawn long enough.

By “you,” psychologist Andrew Gallup of the State University of New York at Oneonta and his colleagues mean “your species.” In the paper in Biology Letters, they report that the average duration of yawns in 109 individuals from 19 species — from humans, African elephants, and walruses to mice, and rabbits, and capuchin monkeys — predicts a species’ brain weight and its number of cortical neurons.

While that may seem like just another bizarre correlation, it has at least some biological plausibility. In 2007 Gallup proposed what has become known as the thermoregulatory theory of yawning. It holds that opening our jaws and sucking in air cools the brain, something other labs have found support for. Yawning might also kick the brain out of its so-called default mode — a sort of background humming-along state — and into a paying-attention state by increasing the circulation of cerebrospinal fluid, a 2014 paper found.

Yawning can increase blood flow to the brain via jaw stretching and the deep inhalation of air, replacing warmed blood in the brain with cooler blood from the heart, and allowing heat exchange with the ambient air, which is almost always cooler than body temperature.

“Longer and/or [more] powerful yawns should provide greater physiological effects,” Gallup said. That prompted a prediction: yawn duration should correlate with brain size and complexity, since having a larger and more neuron-dense brain might require more blood flow.

To test that idea, he and his colleagues timed yawns captured in YouTube videos. The duration varied from 0.8 seconds (mice) to 6.5 seconds (people). Camels, which may have greater mental reserves than they’re credited with, came in at 4.8 seconds, while dogs’ average yawn took 2.4 seconds. STAT would never weigh in on the eternal dogs vs. cats argument, but we’ll mention that cats’ yawns took an average of 1.97 seconds.

The connection to brain weight and neuron numbers wasn’t simply a matter of big jaws producing longer yawns. Gorillas, camels, horses, lions, walruses, and African elephants all have shorter average yawns than people, despite their larger jaws.

The yawning-as-brain-cooling hypothesis remains contentious, however. Critics argue that no matter how wide and how long you open your jaws and suck in air, it doesn’t appreciably cool the brain. Gallup said he has answered the key criticisms, adding, “Whether yawning functions specifically to cool the brain can still be debated, but there is no debate on whether yawning has thermoregulatory consequences.”

Might the number of seconds your own yawns last allow your brain to be larger and more neuron-filled than that of someone whose yawns end in the blink of an eye? The question of whether individual variation within a species matters, Gallup said, “remains an empirical question,” one he is testing with human subjects.

We’ll add only that average yawn duration in the new study was highly correlated with brain weight with a correlation coefficient of 0.91 (or 0.65 after controlling for brain size) with a p value of .001 and also highly correlated with the number of cortical neurons between taxa with a correlation coefficient of 0.95 and a p value of .001, and . . . .

You’re welcome.

SEE ALSO: LSD makes people more optimistic and researchers want to understand why

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NOW WATCH: These secret codes let you access hidden iPhone features

For thousands of years, throughout recorded history, people have searched for a way to live longer.

And we've made remarkable strides, especially in the past century and a half or so. But we may now be butting up against a natural limit to the human lifespan, according to an analysis published October 5 in Nature.

The authors of the analysis say that their data indicates that even if we continue to cure diseases that affect people in old age, no one is likely to significantly outlive the Frenchwoman who holds the record of the human with the longest known life, Jeanne Calment.

She was 122 years old when she died, in 1997.

The essential question, according to authors Xiao Dong, Brandon Milholland, and Jan Vijg, is whether or not our maximum lifespan is flexible, like that of some organisms, or whether biological factors mean that limit is fixed. But while they write that the data they've analyzed "strongly suggest that human lifespan has a natural limit," that doesn't mean humanity could never find a way to break that limit.

What the data show

To answer that central question, the authors of the paper analyzed demographic data from 41 countries around the globe.

Historically, life expectancy first started to drastically shoot up in the past hundred years or so because we'd eliminated many deaths that occurred early in life. The introduction of antibiotics, aggressive vaccination campaigns, and measures to reduce infant and maternal mortality ensured that many more people were able to reach old age.

In more recent years there were slower but significant improvements in late-life mortality, meaning that more and more elderly people lived longer. But those changes appeared to plateau around 1980, the authors write, which they say indicates the possibility of a limit on human life.

To further evaluate this question, the authors analyzed the death rates of supercentenarians (people 110 years of age or higher) in the US, UK, Japan, and France. Though limited numbers of supercentenarians exist, which means that the data on their death rates is not conclusive, the maximum reported age of death in this group seems to have plateaued as well around 1995 — just two years before the death of Calment.

Even the healthiest people who seem to have the ideal genes for l0ngevity have not lived longer since then. The authors write that the chances of someone living past 125 in any given year are less than 1 in 10,000.

Can we break the limit?

In many ways the essential question right now — among tech billionaires trying to defeat death or among researchers and philosophers convinced we can "slay the dragon" of age — is whether or not humans can outlive whatever natural limits we might have.

The authors of the Nature analysis write that they think the limits on human life are not necessarily set by the diseases that kill us when we're old, but by the processes through which our bodies develop throughout our life. We need to change and grow and become able to reproduce, but along the way these physical changes set in motion a process that has a natural endpoint. After that, our cells and bodies are unable to continue. Even curing diseases like cancer and Alzheimer's might not make humans live longer, though the ends of our lives might certainly be better.

For that reason, many of today's current anti-aging researchers are focused on the idea of improving what's called healthspan as much as they are on improving lifespan. (Who would want to live forever if their bodies and minds continued to decline, like Tithonus of Greek mythology?)

Researchers know that aging itself is far more complicated and intertwined with humans' basic biology than just being a side effect of the individual diseases that usually end our lives. That highlights the challenge of trying to treat aging but it also means they understand the complexity of the problem.

"Treating aging used to be just an idea that was confronted with skepticism,"Valter Longo, a professor of gerontology and biological science and the director of the University of Southern California Longevity Institute, told me in a recent interview.

But now Longo believes that there might be enough support for research that helps us figure out how to take the science of life extension further, though he agrees that healthspan must be improved at the same time. He has developed a diet that he says he thinks could increase average lifespan by about 10% (average lifespan still being far less than the lifespan of centenarians but more relevant to a normal person), but that could also keep people much healthier throughout that life.

Jan Vijg, a genetics and aging researcher and one of the authors of the paper, tells Andrew Joseph and Natalia Bronshtein of Stat News that he doesn't think it's likely we'll figure out how to treat all the intricacies of aging: "What are you going to do? Develop a drug for all of them?"

And right now, it might be hard to imagine an answer to that. But 2oo years ago it may have been impossible for most people to imagine surviving to 80 years of age or to conceive of the idea that humans would be planning to send people to Mars. Vijg tells Stat that what he thinks impossible could certainly change.

It's that remarkable challenge that sent Longo and others down the path of trying to "solve" aging in the first place.

"It was the most fantastic thing you could possibly study," says Longo. And an eventual answer may reveal ways to exceed even those natural limits we may have.

SEE ALSO: There’s even more evidence that one activity could help slow the aging process

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NOW WATCH: Scientists discovered something 'shocking' that could rewrite a key part of human evolution

Our gut does more than help us digest food; the bacteria that call our intestines home have been implicated in everything from our mental health and sleep, to weight gain and cravings for certain foods. This series examines how far the science has come and whether there's anything we can do to improve the health of our gut.

The gut microbiota is the community of bugs, including bacteria, that live in our intestine. It has been called the body's "forgotten organ" because of the important role it plays beyond digestion and metabolism.

You might have read about the importance of a healthy gut microbiota for a healthy brain. Links have been made between the microbiota and depression, anxiety and stress. Your gut bacteria may even affect how well you sleep.

But it can be difficult to work out exactly how far the science has come in this emerging field of research. So what evidence is there that your gut microbiota affects your brain?

How does your gut talk to your brain?

When you're healthy, bacteria are kept safely inside your gut. For the most part, the bacteria and your gut live in harmony. (The gut has been known to nurture or even control the behaviour of the bacteria for your well-being.)

So how do the bacteria get their signal out?

The best evidence is that the normal channels of communication from your gut are being hijacked by the bacteria.

The gut has a bidirectional relationship with the central nervous system, referred to as the "gut-brain axis". This allows the gut to send and receive signals to and from the brain.

A recent study found that the addition of a "good" strain of the bacteria lactobacillus (which is also found in yoghurt) to the gut of normal mice reduced their anxiety levels. The effect was blocked after cutting the vagus nerve – the main connection between brain and gut. This suggests the gut-brain axis is being used by bacteria to affect the brain.

This link was clarified in a study where bacterial metabolites (by-products) from fibre digestion were found to increase the levels of the gut hormone and neurotransmitter, serotonin. Serotonin can activate the vagus, suggesting one way your gut bacteria might be linked with your brain.

There are many other ways gut bacteria might affect your brain, including via bacterial toxins and metabolites, nutrient-scavenging, changing your taste-receptors and stirring up your immune system.

How can the gut affect your mental health?

Two human studies looked at people with major depression and found that bacteria in their faeces differed from healthy volunteers. But it's not yet clear why there is a difference, or even what counts as a "normal" gut microbiota.

In mouse studies, changes to the gut bacteria from antibiotics, probiotics (live bacteria) or specific breeding techniques are associated with anxious and depressive behaviours. These behaviours can be "transferred" from one mouse to another after a faecal microbiota transplant.

Even more intriguingly, in a study this year, gut microbiota samples from people with major depression were used to colonise bacteria-free rats. These rats went on to show behavioural changes related to depression.

Stress is also likely to be important in gut microbiota and mental health. We've known for a long time that stress contributes to the onset of mental illness. We are now discovering bidirectional links between stress and the microbiota.

In rat pups, exposure to a stressor (being separated from their mums) changes their gut microbiota, their stress response, and their behaviour. Probiotics containing "good" strains of bacteria can reduce their stress behaviours.

How gut microbiota affects your mood

Medical conditions associated with changes in mood, such as irritable bowel syndrome (IBS) and chronic fatigue syndrome (CFS), might also be related to gut microbiota.

IBS is considered a "gut-brain disorder", since it is often worsened by stress. Half of IBS sufferers also have difficulties with depression or anxiety.

Ongoing research is investigating whether gut bacteria are one reason for the mood symptoms in IBS, as well as the gastrointestinal pain, diarrhoea and constipation.

Similarly, CFS is a multi-system illness, with many patients experiencing unbalanced gut microbiota. In these patients, alterations in the gut microbiota may contribute to the development of symptoms such as depression, neurocognitive impairments (affecting memory, thought and communication), pain and sleep disturbance.

In a recent study, higher levels of lactobacillus were associated with poorer mood in CFS participants. Some improvements in sleep and mood were observed when patients used antibiotic treatment to reduce gut microbial imbalance.

The exact contributions of stress and other factors such as intestinal permeability (which allows nutrients to pass through the gut) to these disorders are not understood. But the downstream effects seem to be involved in IBS, inflammatory bowel conditions, CFS, depression and chronic pain.

How our gut affects our sleep

Our mental health is closely linked to the quality and timing of our sleep. Now evidence suggests that the gut microbiota can influence sleep quality and sleep-wake cycles (our circadian rhythm).

A study this year examined patients with CFS. The researchers found that higher levels of the "bad" clostridium bacteria were associated with an increased likelihood of sleep problems and fatigue, but this was specific to females only. This suggests that an unbalanced gut may precipitate or perpetuate sleep problems.

There is emerging evidence that circadian rhythms regulate the gut immune response. The effect of immune cells on the biological clock could provide insights into the possible bidirectional relationship between sleep and the gut. For example, data from animal studies suggests that circadian misalignment can lead to an unbalanced gut microbiota. But this effect can be moderated by diet.

There is growing concern that disruptions to our circadian timing of sleep leads to a range of health issues, such as obesity, metabolic and inflammatory disease, and mood disorders. This is particularly important for shiftworkers and others who experience changes to their sleep/wake patterns.

What this means for treatment

In terms of using interventions directed at the gut to treat brain disorders – so called "psychobiotics"– there is a lot of promise but little clear evidence.

Probiotic (live bacteria) treatments in mice have been shown to reduce cortisol, an important stress hormone, and decrease anxious and depressive behaviours.

But there are very few studies in humans. A recent systematic review of all the human studies showed the majority do not show any effect of probiotics on mood, stress or symptoms of mental illness.

On the plus side, large studies show us that people who eat a balanced diet with all the usual good stuff (fibre, fresh fruit and vegetables) have lower rates of mental illness as adults and adolescents.

Clearly, diet affects both the gut microbiota and mental health. Research is ongoing to see whether it is a healthy gut microbiota that underlies this relationship.

A healthy gut microbiota is linked to a healthy brain. However there are only a handful of human studies demonstrating real-world relevance of this link to mental health outcomes.

There is still a way to go before we can say exactly how best to harness the microbiota in order to improve brain function and mental health.

Paul Bertrand, Senior Lecturer in School of Health and Biomedical Sciences, RMIT University; Amy Loughman, Associate Lecturer, Industry Fellow, RMIT University, and Melinda Jackson, Senior Research Fellow in the School of Health and Biomedical Sciences, RMIT University

This article was originally published on The Conversation. Read the original article.

SEE ALSO: Researchers are trying to figure out how to change your brain so you can learn like a kid again

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NOW WATCH: Clinton opens up a massive lead against Trump, with lopsided support from a key voting demographic

Israeli startup Faception made headlines this year by claiming it could predict how likely people are to be terrorists, pedophiles, and more by analyzing faces with deep learning.

It's an unsettling idea. Experts and research in the field, however, suggest that it is more fantasy than reality.

Faception assigns ratings after training artificial intelligence on faces of terrorists, pedophiles, Mensa members, professional poker players, and more. Through deep learning—that emerging technique found in everything from Alpha Go to Siri to Netflix—the AI can supposedly predict how likely a new face is to belong to any given group.

While this may sound believable, there's no evidence that face-based personality predictions are more than a tiny bit accurate. And there are many reasons to fear it might promote bias and other dangerous effects.

Face-based predictions of personality are extremely limited.

There's a long history of trying to predict personality from faces. Called physiognomy, it's been largely refuted.

"Impressions from faces are very, very low quality evidence," said Alexander Todorov, a Princeton psychologist who specializes in facial perception. "You’re going to make important decisions, whether someone’s competent or fits the job, based on their appearance? That’s a ridiculous notion."

Although Todorov's work focuses on human perception of faces, AI doesn't seem to be much better.

Forthcoming papers out of Switzerland and the US show that deep learning models using social media profile pictures were able to explain only 2-to-3% of variation in personality scores. By comparison, predictions using Facebook likes were able to explain over 30%.

What Faception is trying to do is even harder. Rather than use carefully curated profile pictures, which give clues to personality in style, scene, and pose, it uses relatively neutral images like passport photos and security camera stills.

The startup tries to get around this limitation by looking at a wider range of variables, notably facial structure and other inherent physical differences, hoping to uncover genetic influences in personality.

For now, there's little proof that this works.

"Current psychological research shows that by adulthood, personality is mostly influenced by the environment," wrote Daniel Preotiuc-Pietro, a post-doctoral researcher at the University of Pennsylvania who has worked on predicting personality from profile images, in an email. "While it is potentially possible to predict personality from a photo, this is at best slightly better than chance in the case of humans. I seriously doubt the 80% accuracy for personality [claimed by Faception]."

Faception is also on uncharted territory when it comes to predicting behavior, rather than personality, from facial traits. It's one thing to spot an extrovert and another to spot a terrorist.

It's true that Faception has access to cutting-edge research. One of its advisors is Michal Kosinski, the Stanford social psychologist who showed that you can effectively predict personality traits using Facebook likes. Kosinski is currently finalizing a study that he says will show that you can make pretty good predictions based on faces too.

"It is easy to infer age and gender from your face. It turns out you can also infer things like personality, sexual orientation, and so on," said Kosinski.

Kosinski said his models can make predictions based on facial traits that are tied to individual differences in people's hormones and genes, but he wouldn't say how accurate those predictions are. He also wouldn't comment on Faception's approach, noting that he doesn't know the inner workings, except to say that it could work in theory.

Faception claims to be highly accurate. The company says its models would have flagged eight of 11 of the Paris attackers and that in a 50-person poker tournament, its four picks included two of the three finalists. CEO Shai Gilboa also tells us it has reached over 90% accuracy on some classifiers. It's not clear what these claims really mean, however, and it's impossible to verify them.

"The problem with this kind of commercial application is that it’s very hard to evaluate the evidence because nothing is published and you don’t know what they have done," said Todorov.

All that's to say there's little evidence that Faception’s methods would yield reliable results. Given that, it's frightening to imagine how they might be used.

Facial profiling with deep learning could be dangerous.

Where to start? For one, there's the risk of false positives.

"Even if there’s good evidence, better than chance, what are the costs when you make an error?" said Todorov. "It’s stigmatizing and it has a lot of ramifications."

In fact, false positives are inevitable with classifiers looking at things like terrorists.

"Even the most accurate model aimed at a rare outcome will produce a great majority of false positives—extremely rare 'true positives,' like being a terrorist, will be hidden among thousands or hundreds of thousands of 'false positives,'" said Kosinski.

If you don't think that's a problem, imagine how you'd feel if word leaked that you were at at high risk of being a terrorist or pedophile.

Another risk is that algorithms might fail to disassociate ethnicity, gender, and other factors. Then a model supposedly looking at facial traits could really be a cover for even more controversial kinds of discrimination.

"The possibility of encoding biases is very real," wrote Preotiuc-Pietro. "An algorithm is trained to optimize its accuracy and this may lead to over-representing stereotypes."

Examples of algorithms falling into this trap are increasingly common. A ProPublica investigation earlier this year found that software used to predict criminality is biased against black people. Another study found that women are shown fewer online ads for high-paying jobs. Then there was the AI beauty contest that was biased in favor of white people.

There are ways to try to guard against bias in facial profiling.

"One is to separate models for different groups of people," Kosinski wrote in an email. "Second, is to analyze the results separately for different groups. One could, for instance, look more closely at the suspects in a given group that are in top x% of the scores, regardless of the fact that even the most 'terrorist-looking' female face is probably much less terrorist looking (in [the] model’s eyes) than most 'terrorist-looking' male."

Gilboa wouldn't go into details about how Faception avoids bias but insisted it wasn't a problem: "We don't [make] such mistakes."

The risk is that this kind of discrimination can reinforce stereotypes, alienate broad groups of people, and distract from other information that is more useful.

"Do you know the book, 'Moneyball?' Todorov asked, referring to the account of a baseball executive who questioned assumptions about what makes a good player. "That’s a great book and this is exactly, exactly the opposite point of view. What explains the success of Billy Bean? Well, because he didn’t believe in appearance."

Facial profiling is on the rise

Whatever you think about facial profiling, it's not going anywhere.

Faception, for one, claims to be off to a good start. Gilboa told us the startup has been hired to analyze security risk for unnamed governments and default risk for unnamed financial clients. He said it is also focused on developing applications to improve human-robot interactions through personalization.

Faception could succeed, even if it is highly inaccurate, even if it is highly unsavory. If its models can make banks, security agencies, and other groups feel they are ever so slightly better as evaluating people, then it might have a market. After all, facial profiling has the advantage of working in the absence of any private data.

And this could be just the start.

"There’s a fast-growing interest in this technology," said Kosinski. "I’ve seen some startups [in the area] and I’m also sure that companies like Facebook and Google and Microsoft have plenty of people who are computer vision specialists and also are very strong on the deep learning front."

"Once the knowledge is there," said Todorov, "I wouldn’t be surprised if some people, companies, businesses buy into it."

No doubt some of these applications will help the world.

"The benefits are mind-blowing," said Kosinski. "For instance, predicting illness—if you have a technology that can take a picture of your face and say you might have diabetes or something."

Other applications are more controversial.

"If crossing a border to a country that is less liberal and less concerned with human rights than the United States, they don’t even need to get data," said Kosinski. "They can just take a picture of your face and then have a prediction of political affiliation."

One thing is for sure, said Kosinski: "It’s going to be very bad for privacy."

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