New Study Shows It's Surprisingly Easy to Make People Have Auditory Hallucinations

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iStock

If you’ve ever heard something that wasn't there—an auditory hallucination—you know that the sound seems very, very real. A new study suggests that it's easy to induce auditory hallucinations in people, but it's even easier in people who already claim to hear things that aren't there. The research was published in the journal Science.

Co-author Al Powers is a psychiatric researcher at Yale. Speaking in a study, he said hallucinations “…may arise from an imbalance between our expectations about the environment and the information we get from our senses.”

In other words, he says, "You may perceive what you expect, not what your senses are telling you."

Powers and his colleagues recruited 59 people to help them test that hypothesis. There were four groups of participants: people who heard voices and had been diagnosed with psychosis; people who had been diagnosed with psychosis but didn’t hear voices; people who heard voices but had not been diagnosed with any mental illness (we'll come back to that in a moment); and people who just plain didn't hear voices.

The third group was an unusual one: 15 self-professed psychics. These participants said that they heard voices every day, but unlike people in the first group—those diagnosed with psychosis who heard voices—they weren't bothered by the voices they claimed to hear. In fact, they took them to be communications from supernatural forces or entities.

All the participants then underwent brain scans. While they were in the scanner, the researchers used a combination of sounds and images to trick their brains into producing auditory hallucinations. First, participants were shown a checkerboard and played a sound. Then they were told to listen for the sound. Sometimes it played when the checkerboard appeared. Sometimes it didn't play at all, but the checkerboard showed, which led their brains to expect the sound would be played.

Members of all four groups experienced the hallucinations, hearing noises even in the silence. Their brain scans showed that they really were "hearing" the nonexistent sounds.

Unsurprisingly, the two groups of hallucination-prone people were more susceptible to hearing things. But when they were told that there had in fact been no sound, people with psychosis were less likely to believe it. 

The authors say this difference could potentially help doctors spot, diagnose, and treat psychosis in their patients before it becomes severe.

Lost Your Wallet? You Might Be More Likely to Get It Back If There's Cash Inside

iStock/tzahiV
iStock/tzahiV

Few things can incite more panic than discovering you’ve lost a wallet or purse containing money, identification, credit cards, and/or keys. You wonder if anyone will find it—and if they do, whether they’ll decide to retain your cash using the playground ethics of the "finders keepers" rule.

An ambitious new study in the journal Science has provided at least a partial answer. If your wallet has cash inside, it’s actually more likely for people to return it than if it didn’t have any.

Researchers at the University of Michigan conducted an exercise in civic honesty, dispatching 13 assistants to 355 cities in 40 countries across the globe. At each destination, the assistants were armed with clear wallets that held things like grocery lists and business cards along with an email address. Some wallets had no money inside. Others contained about $13.45 in the local currency. The assistants gave the wallets to employees at banks, hotels, post offices, museums, and police stations, explaining they had “found” the wallet and were in too big of a hurry to contact the owner themselves. They passed the responsibility to the person receiving the wallet. All told, 17,303 wallets were left as proverbial bait to see what the employees might do.

Of the wallets without cash inside, researchers received an email seeking to return roughly 40 percent of them. About 51 percent of the employees attempted to return the wallets containing $13.45 in cash.

These percentages fluctuated by country. In Denmark, 82 percent of wallets with cash were returned. In the United States, the figure was 57 percent. When researchers upped the stakes by including $94.15 in wallets for areas in the U.S., Britain, and Poland, the return rate went up to 72 percent.

It’s difficult to infer motivations for why people returned wallets with more money than less, or none. In a survey, researchers found that people in general described wanting to avoid feeling like a thief by keeping the money. (Respondents were different than the employees who were left with the wallet.) That would explain why returns increased as the dollar amount went up.

The study was limited by the fact that the wallets were left with people who could have presumably been held accountable for not returning them. The research assistant could have returned to inquire about the wallet’s status, while no such concern exists for people finding a wallet in the street. Still, it does indicate that people feel a measure of sympathy for—and moral obligation to—lost money and will make an effort to see it returned.

[h/t Science News]

Some Fish Eggs Can Hatch After Being Pooped Out by Swans

iStock/olaser
iStock/olaser

A question that’s often baffled scientists is how certain species of fish can sometimes appear—and even proliferate—in isolated bodies of water not previously known to harbor them. A new study has demonstrated that the most unlikely explanation might actually be correct: It’s possible they fell from the sky.

Specifically, from the rear end of a swan.

A study in the journal Ecology by researchers at the Unisinos University in Brazil found that killifish eggs can, in rare cases, survive being swallowed by swans, enduring a journey through their digestive tracts before being excreted out. This kind of fecal public transportation system explains how killifish can pop up in ponds, flood waters, and other water bodies that would seem an unlikely place for species to suddenly appear.

After discovering that some plants could survive being ingested and then flourish in swan poop, researchers took notice of a killifish egg present in a frozen fecal sample. They set about mixing two species of killifish eggs into the food supply of coscoroba swans living in a zoo. After waiting a day, they collected the poop and dug in looking for the eggs.

Of the 650 eggs they estimated to have been ingested by the swans, about five were left intact. Of those, three continued to develop. Two died of a fungal infection, but one survived, enduring 30 hours in the gut and hatching 49 days after being excreted.

Because killifish eggs have a thick outer membrane, or chorion, they stand a chance of coming through the digestive tract of an animal intact. Not all of what a swan ingests will be absorbed; their stomachs are built to extract nutrients quickly and get rid of the whatever's left so the birds can eat again. In rare cases, that can mean an egg that can go on to prosper.

Not all fish eggs are so durable, and not all fish are quite like the killifish. Dubbed the "most extreme" fish on Earth by the BBC, killifish have adapted to popping up in strange environments where water may eventually dry up. They typically live for a year and deposit eggs that can survive in soil, delaying their development until conditions—say, not being inside a swan—are optimal. One species, the mangrove killifish, can even breathe through its skin. When water recedes, they can survive on land for over two months, waddling on their bellies or using their tails to "jump" and eat insects. A fish that can survive on dry land probably doesn't sweat having to live in poop.

The researchers plan to study carp eggs next to see if they, too, can go through a lot of crap to get to where they’re going.

[h/t The New York Times]

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