Field of Science


Whale Turns Down Its Hearing When Expecting Loud Sounds

We can knit sweaters for oiled penguins, but it's harder to protect whales and dolphins from the harm of having us as neighbors. Loud underwater sounds from activities like sonar and drilling may damage these animals' hearing and even lead to mass strandings. Though we can't chase cetaceans around with homemade earmuffs, we might be able to teach them to tune us out.

Like squinting or letting one's pupil shrink in bright light, some animals can adjust how sensitive their ears are. When we're making loud noises, humans reflexively squeeze the muscles of the middle ear to dampen our hearing. Some bats do the same thing while echolocating.

"Generally speaking, mammals have evolved mechanisms to protect their auditory systems from self-produced intense sounds," write Paul Nachtigall of the University of Hawaii and Alexander Supin of the Russian Academy of Sciences. In 2008, the pair showed that a false killer whale (Pseudorca crassidens) could adjust its hearing while it echolocated. So they set out to see whether the species could also dial down its hearing in response to sounds made by someone else.

They taught their whale (a female, originally caught in the wild and now thought to be 30 or 40 years old) that hearing a quiet warning sound meant a louder sound was coming soon. The subject wore suction-cup electrodes on her head during the experiment. Waiting at an underwater listening station, she first heard a series of tones while the electrodes measured which ones her ears responded to. Then, a variable amount of time later, she heard a sudden loud sound (170 decibels).

Over hundreds of trials,* the researchers saw that the whale learned to anticipate the loud sound. If it came within 35 seconds of the warning sound starting, the whale was able to desensitize her ears before it played. (With a longer delay, her response wasn't as strong.) The authors report their results in the Journal of Experimental Biology.

Nachtigall can't say how a whale turns down its hearing. "No one knows for sure how the cetacean middle ear works," he says. Whales don't have eardrums like humans or other land animals, he says, because the sounds they hear must travel through tissue instead of air. So his whale subject probably doesn't squeeze her ear muscles to dampen sound, as a human or bat would. He speculates that it's more likely a top-down control from the brain.

However she does it, the whale can make her ears less sensitive when she knows a loud sound is coming soon. The biggest decrease in her hearing sensitivity was about 13 decibels. That's "about what your hearing changes if you stick your fingers in your ears," Nachtigall says. If you—or the whale—are trying to protect your hearing from a loud noise, he says, "That helps. This would help."

When humans must make a racket underwater, it's possible that we could help whales and other animals by making quieter warning sounds beforehand. This could teach the animals to anticipate the sound and "plug" their ears.

Since he's only studied one animal so far, Nachtigall doesn't know how the abilities of other marine mammals to desensitize their ears compare. "To ask whether [warning sounds] would prevent whale hearing damage is sort of like asking whether ear plugs would prevent deafness in people who work next to jet engines," he says. "I believe the possibility is great, but there are more questions to be answered."

Image: by MichiKimmig (Flickr)

Nachtigall, P., & Supin, A. (2013). A false killer whale reduces its hearing sensitivity when a loud sound is preceded by a warning Journal of Experimental Biology DOI: 10.1242/​jeb.085068

*If you're wondering how one convinces a whale to participate in so many trials, the answer is "fish reinforcement."

The Shambulance: Reflexology and Other Stories

The Shambulance is an occasional series in which I try to find the truth about bogus or overhyped health products. Helping me keep the Shambulance on course are Steven Swoap and Daniel Lynch, both biology professors at Williams College.

Sticking a Q-tip up one’s nose is not the source of many great insights. Yet it’s how an American doctor in the early 20th century developed the theory that became modern reflexology. He would be proud—though maybe a little confused—to see people today flocking to reflexology spas, where practitioners treat all their problems via the soles of their feet.

The American doctor in question was William H. Fitzgerald, an ear, nose and throat specialist. In a 1917 book, he explained the genesis of his big idea:
Six years ago I accidentally discovered that pressure with a cotton tipped probe on the muco-cutinous margin (where the skin joins the mucous membrane) of the nose gave an anesthetic result as though a cocaine solution had been applied . . . Also, that pressure exerted over any bony eminence of the hands, feet or over the joints, produces the same characteristic results in pain relief . . . This led to my ‘mapping out’ these various areas and their associated connections and also to noting the conditions influenced through them. This science I have named "Zone Therapy."
Chapter titles from Zone Therapy include "Zone Therapy for Women" (tongue depressor into the back of the throat for menstrual cramps), "Painless Childbirth" (rubber bands around the toes, among other interventions) and "Curing Lumbago with a Comb."

A nurse and physical therapist named Eunice D. Ingham extended the idea of zone therapy in the 1930s and 1940s, eventually mapping the entire body onto the soles of the feet. She called each important point on the foot a “reflex” because it reflected back to a certain organ or body part. Ingham wrote two books on the subject, now called reflexology: Stories the Feet Can Tell and Stories the Feet Have Told.

Today, the International Institute of Reflexology describes its practice as as “a science which deals with the principle that there are reflex areas in the feet and hands which correspond to all of the glands, organs and parts of the body.” Stimulating these points “can help many health problems in a natural way.” The site insists, “Reflexology…should not be confused with massage.”

There has been some confusion and blending, though, between Western reflexology and traditional Chinese medicine. Ingham and Fitzgerald's idea of "zones" is similar to the Chinese principle of "meridians." In traditional Chinese medicine, meridians are paths that carry qi through the body and connect the acupuncture points. Reflexology groups like to say that Fitzgerald "rediscovered" the science from more ancient roots. They even claim that ancient Egyptians practiced it, based on tomb paintings showing people holding each other's feet.

Whoever thought it up first, the idea that the soles of your feet hold a miniature map of the entire rest of your body defies a scientific explanation.

“The problem is communication,” says physiologist Steven Swoap. “How does the foot talk to the pancreas?”

The foot is full of sensory nerves, Swoap explains. These can detect temperature, pain or position and send that information to the spinal cord. If the signal is something urgent—say, you stepped on a nail—the spinal cord will send a quick command back to the foot (“STOP!”). If the signal from the foot is a non-painful one (“Hey, I’m walking on grass”), it will travel all the way up the spinal cord to the brain.

“But in no instance do those sensory nerves bypass either the spinal cord or the brain and go directly to the liver, or the kidney, or the colon,” Swoap says. This means your foot can’t communicate directly with any other body part except your spinal cord or brain. Whatever stories the feet have told, they’ve had a limited audience.

Daniel Lynch, a biochemist, points out that sex organs are missing from some reflexology maps. “Why aren’t the gonads on there?” he asks. Other maps label a "testes and ovaries" region around the middle of the heel, but there's variation from one chart to the next.

Setting aside the map itself, Lynch says, “Where is the evidence that it actually works?”

The evidence is slimmer than a stiletto heel. In a 2011 review paper, complementary medicine researchers at the Universities of Exeter and Plymouth dug up every scientific study of reflexology they could find. Out of 23 randomized clinical trials, only 8 “suggested positive effects.”

The quality of the studies was “variable,” the authors write, “but, in most cases, it was poor.” Only four studies that found a positive effect used a placebo control—that is, did massaging the feet without regard to “zones” give patients the same symptom relief? In general, studies tended to use small groups of subjects and not to be replicated by other researchers.

Reflexology has been tested on conditions including asthma, premenstrual syndrome, irritable bowel syndrome, multiple sclerosis, and back pain. If reflexology does have a benefit, “The most promising evidence seems to be in the realm of cancer palliation,” or making patients more comfortable, the authors write. Overall, though, they found no convincing evidence that reflexology has power beyond the placebo.

Not that we should thumb our Q-tip-free noses at the placebo effect. The body has an impressive power to make itself feel better based on our expectations. A foot rub from a professional may very well ease a person’s pain. If that professional says anything about zones, though, it’s only a story.

Image: Foot reflexology chart by Stacy Simone (Wikipedia)

Ernst, E., Posadzki, P., & Lee, M. (2011). Reflexology: An update of a systematic review of randomised clinical trials Maturitas, 68 (2), 116-120 DOI: 10.1016/j.maturitas.2010.10.011

Scientists Unsure Why Female Flies Expel Sperm and Eat It

She's apparently a picky mater but not a picky eater. The female of a certain fly species, after mating with a male, dumps his ejaculate back out of her body and onto the ground. Then she gobbles it up. Despite new hints that this behavior may help the female choose which partner fertilizes her eggs, or keep her healthy in times of famine, scientists are still a little perplexed by it.

Various female insects, spiders, and birds are known to expel the male ejaculate from their bodies after the deed is done. In some cases, it seems to let them decide which male's sperm reaches their eggs. Females don't always choose who mates with them, but that doesn't mean they have no choice in their progeny's fatherhood. (This kind of female choosiness about sperm can lead to evolutionary arms races between males and females. The "copulatory plug" is a popular tool among male insects, spiders, reptiles, and even some mammals.)

Eating the ejaculate, as Euxesta bilimeki does, is less popular. This fly lives on agave plants and mates pretty much all the time. "Females can be observed escaping male advances in chases that can last more than an hour," write Christian Luis Rodriguez-Enriquez and his coauthors from the Instituto de EcologĂ­a in Veracruz, Mexico. Using videocameras and careful meal planning, they tried to divine a reason for the female flies' behavior.

Out of 74 females that the researchers recorded mating, every one expelled and ate the ejaculate afterward. The researchers then killed the females and pulled them apart with tweezers to look for sperm inside their various storage locations. They found that three-quarters of the females had kept some sperm from their male partner, while one-quarter had expelled it all.

There was no obvious rule to which sperm the females kept. There were some patterns, though. For example, females that mated with larger males, then waited longer before expelling the sperm, were more likely to keep some. Since the female's behavior doesn't seem random—and since it's possible for her to keep no sperm at all—the authors think she may be choosing between mates after the fact.

This could explain why the female expels the sperm, but not why she eats it. In another experiment, researchers fed female flies various diets and measured whether supplementing those diets with ejaculate made them healthier. When female flies were starved entirely, the extra snack did help them live longer—but under normal circumstances there was no difference. The authors report their results in Behavioral Ecology and Sociobiology.

"Our study appears to have raised more questions than provided answers," the authors admit. They expected there would be some clear nutritional benefit to justify the females' tastes.

Rodriguez-Enriquez and his coauthors speculate that the ejaculate-as-meal habit may have evolved as a "nuptial gift." This is an edible present that male insects sometimes give to females as part of their courtship. Usually it's nutritious—a nicely wrapped dead bug, say—but in some cases it's just an empty sac. The ejaculate may be, like these gifts, just an edible empty gesture.


(The above is a video of Euxesta bilimeki flies mating. It doesn't look any different from what you're imagining, but the soundtrack is a nice twist.)

Rodriguez-Enriquez, C., Tadeo, E., & Rull, J. (2013). Elucidating the function of ejaculate expulsion and consumption after copulation by female Euxesta bilimeki Behavioral Ecology and Sociobiology DOI: 10.1007/s00265-013-1518-5

Image and video: Rodriguez-Enriquez et al.

Google Promises We'll Feel Better in the Summer

Shakespeare wasn't kidding about the "winter of our discontent." In the colder and darker months, people do more internet searches for mental health terms, from anxiety and ADHD all the way to suicide. Search patterns also promise that like a refreshed browser window, better times are due to arrive soon.

John Ayers, of the Center for Behavioral Epidemiology and Community Health in San Diego, and other researchers dove into Google Trends to explore whether certain searches vary by season. "Seasonal affective disorder is one of the most studied phenomena in mental health," Ayers says, "with many individuals suffering mood changes from summer to winter due to changes in solar intensity." He wanted to find out whether any other mental health complaints changed with the seasons, as some studies had hinted.

Since Google Trends breaks down searches by category, the researchers started in the "mental health" section. Looking at all mental health searches in the United States between 2006 and 2011, they saw a consistent cycle with peaks in the winter and troughs in the summer. (If you do this search yourself, you'll see that there's also a dip around the December holidays—but the curve reliably bottoms out in July of each year.)

The team did some statistical smoothing and found that mental health searches overall were about 14% higher in the winter than in the summer. To confirm that the difference was due to the season, they ran the same analysis on data from Australia. Searches cycled in the same way—about 11%  higher in winter than summer—but the peaks in the southern-hemisphere country were almost exactly 6 months out of sync with the United States.

When the scientists broke down searches by specific symptoms or illnesses, the seasonal cycle remained—and in some cases got much stronger. "We were very surprised" to see this, Ayers says. Searches including the terms ADHD, anxiety, bipolar, depression, anorexia or bulimia, OCD, schizophrenia, and suicide all rose in the winter and fell in the summer.

One of the most dramatically cycling search terms was schizophrenia, at 37% higher in the winter. Eating disorder terms varied just as strongly. (The smallest seasonal difference was for anxiety, which was just 7% higher in the winter in the United States, and 15% in Australia.)

Some of this seasonality might be due to the schedule of the school year, Ayers points out. Referrals for kids with ADHD and eating disorders may come from their schools.

Other explanations involve winter itself. The effect of shorter days on our circadian rhythms and hormone levels might be a factor, the authors write, as in seasonal affective disorder. They speculate that a lack of vitamin D (which we make using sunlight) in the winter might contribute. Even omega 3 fatty acids might matter: we consume less of them in winter, and omega 3 deficiency has been linked to some mental illnesses.

There's also the question of what we're doing all season. People hunkered indoors during the colder months may have fewer chances for socializing, which is "a well-known health emollient," the authors write. The same goes for physical activity.

"There is a lot more we need to learn about mental health and seasonality," Ayers says. "For instance, is there a universal mechanism that impacts our mental health?"

Of course, sometimes our malaise isn't about the season.

Whatever portion of mental health is predictable, though, doctors would love to know about it and use that information to help.

This study doesn't reveal much about low-income or elderly populations who aren't online. And knowing what people are searching for isn't exactly the same as knowing what symptoms they're experiencing. "We are actively working to address these limitations," Ayers says. Working with, the charitable branch of Google, he hopes to develop systems similar to Google Flu Trends that can track a population's mental health.

"Intuition suggests that these results are reflective of an important link between the seasons and mental health," Ayers says. For now, we have the reassurance of computer algorithms that skies will be clearer soon.

Ayers, J., Althouse, B., Allem, J., Rosenquist, J., & Ford, D. (2013). Seasonality in Seeking Mental Health Information on Google American Journal of Preventive Medicine, 44 (5), 520-525 DOI: 10.1016/j.amepre.2013.01.012

Image: Skaneateles, NY, by me.

Homing Pigeons Never Stop Learning Ways to Get Home

A young homing pigeon must learn quickly how to find its way home from the strange neighborhoods where humans insist on leaving it. At first the bird does this by relying on its crudest instincts, returning to its roost along a route full of youthful zigzags. Over time, though, it refines its methods. A mature pigeon takes a much simpler route, because it has drawn itself a more complex map.

Homing pigeons have been subjected to all kinds of research. The latest study used GPS devices, which the birds carried in little Teflon backpacks. Ingo Schiffner of the Queensland Brain Institute and Roswitha Wiltschko of Goethe-Universität Frankfurt studied pigeons at three different ages: juveniles (6 to 7 months old), yearlings (the same pigeons in their second year of life, after going through a training program), and older trained birds (at least two years of age).

Wearing their tracking harnesses, the birds were released from various sites that ranged from 3.2 to 23.5 kilometers away from their home loft in Frankfurt, Germany. Here are the routes some of the birds took when returning to their home (the square) from a release site 6.8 kilometers away (the triangle):

You'll notice that some pigeons traveled by more, shall we say, scenic routes than others. The researchers calculated each bird's "efficiency" and found that the youngest group of pigeons were the least direct fliers. On average, they traveled more than three times the distance of a straight-line trip between the two points. (The pigeon researchers, in a bit of a mixed-species metapor, refer to this ideal trip as a "beeline.")

The two older groups of birds were much more efficient, flying no more than 25 percent farther than they needed to. Since their youthful zigzagging days, they had gone through a training program that had them practicing as far as 40 kilometers from their home roost. Now more familiar with the features of the landscape around their home, they could navigate it easily.

But that didn't mean the pigeons stopped refining their internal maps after their first year. Schiffner and Wiltschko also calculated something called the "correlational dimension," which is the number of factors that seem to be contributing to a system—in this case, pigeon navigation. 

Previous research has suggested that homing pigeons have multiple tools in their navigational toolkit. In various experiments, "pigeons have been deprived of visual cues, magnetic cues, olfactory cues, infrasound cues, and their gravitational sense," Schiffner says, "yet pigeons are still able to find their way home." Rather than relying on just one tool at a time, they seem to use several.

The correlation dimension is meant to count how many tools each pigeon uses to complete a trip. The youngest pigeons usually hovered close to 2. But year-old pigeons had a somewhat higher score, and the oldest pigeons were closer to 3. In his previous research, Schiffner says, pigeons have seemed to use as many as 4 types of navigational cues simultaneously. 

This suggests that pigeons keep refining their mental maps as they age, adding new elements—visual landmarks, say, or the smell of a local factory—to others such as sunlight and magnetic fields. "I cannot say yet which factors pigeons are using," Schiffner says, but he believes the factors add up with age. He and Wiltschko report their results in the Journal of Experimental Biology. Schiffner adds, "I assume that pigeons continue to learn and integrate new information into their navigational map as they grow older."

Attaching GPS devices to animals is currently trendy; there's a whole new journal dedicated to the subject. But humans have a long history of rigging our technologies to pigeons. At the start of the 20th century, German apothecary Julius Neubronner designed and patented a little camera on a harness for homing pigeons to carry (he had previously used the birds to ferry prescriptions and drugs for his patients).

The German military toyed with using Neubronner's pigeon-camera technology for reconnaissance during World War I. With the cameras hooked to timers, the birds could take pictures above enemy lines and carry them back home. These days we're attaching our instruments to the accommodating birds not for the sake of spying on our enemies, but to decode the secrets of the pigeons themselves.

Images: Homing pigeons by Amanda Dague (via Flickr); figure from Schiffner and Wiltschko; pigeon cameras by Julius Neubronner (via Wikimedia Commons).

Schiffner, I., & Wiltschko, R. (2013). Development of the navigational system in homing pigeons: increase in complexity of the navigational map Journal of Experimental Biology DOI: 10.1242/jeb.085662

Rubber Hand Experiment Shows Kids Have More Flexible Body Boundaries

Close your eyes. Do you know where all your fingers and toes are? Can you pinpoint the exact edges of your body in space?

You may think your knowledge of your body is unshakeable, but a simple trick with a rubber limb can sway you. In kids, the effect is even more extreme—a finding that gives intriguing hints about how our body sense develops.

The new research relies on the "rubber hand illusion," first published in 1998. To produce this illusion, an experimenter sits across a table from a subject. The subject rests one hand, let's say the left, flat on the table and keeps the other hand in his lap. A little wall blocks the left hand from the subject's sight. But the subject can see a rubber hand, also a left hand, sitting on the table just inside the wall.

Actually, hold on, I'll draw you a picture.

OK. The experimenter (or, oval with glasses) holds two paintbrushes and uses them to stroke the backs of the real hand and the rubber one simultaneously. The subject watches these paintbrush strokes that seem to match the ones he's feeling, and eventually the brain takes a shortcut: it decides the seen hand and the felt hand are one and the same. This gives the subject the eerie impression that the rubber hand is part of his body. (I wrote about trying the rubber hand experiment for my eighth-grade science fair—and someone else's kooky version of the illusion that uses entire bodies instead of hands—here.)

University of London psychologist Dorothy Cowie and her colleagues tested the rubber hand illusion on kids of varying ages to see how their response compared to adults. Like researchers before them, they measured the effect in two ways. The first was a questionnaire about whether the rubber hand felt like the subject's own (for kids, the scale went from "definitely not" to "lots and lots").

For the second measurement, subjects closed their eyes and slid the index finger of their right hand under the edge of the table until they believed it was aligned with the index finger of their left hand. After experiencing this illusion, subjects tend to get skewed in the direction of the rubber hand.

The researchers tested adults as well as 90 kids between the ages of 4 and 9. They saw that in the sliding-finger measurement, kids in all age groups drifted farther toward the rubber hand than adults did. The results are reported in Psychological Science.

To explain this, Cowie suggests that people rely on two different methods to figure out where their body parts are. One combines vision and touch: do the cues I'm feeling match what I see? The illusion worked best for adults when the paintbrush strokes on both hands were perfectly in sync.

But for kids, the illusion stayed strong even when the paintbrush strokes they saw were out of sync with the ones they felt. This suggests that a second system of perception simply asks whether something that looks like our arm appears in roughly the place we expect it. Kids overuse this system, Cowie says. "Seeing a 'hand-like thing' in front of them on the table was enough to sway their perception of where their own hands were." By adulthood, Cowie thinks, we learn to pay more attention to tactical cues. "Adults rely less on the visual stuff than kids."

The fact that the illusion works at all demonstrates that "we don't just rely on muscle info to tell us where our body is," Cowie says, whether we're kids or adults. "In fact vision is really important!" Her research group is conducting further studies to find out how perception changes with age. "The results are absolutely always that kids are more susceptible than adults" to the illusion, she says.

If you're feeling worried that you don't know your body very well, consider taking on a more childlike attitude. Cowie says the kids in her experiment enjoyed being tricked by the illusion. One kid reacted with "You seem to have painted my hand!" They were eager to check where their hands really were when the test was over.

"Kids are actually open to weird stuff more than adults are," she says.

Cowie, D., Makin, T., & Bremner, A. (2013). Children's Responses to the Rubber-Hand Illusion Reveal Dissociable Pathways in Body Representation Psychological Science DOI: 10.1177/0956797612462902

Images: St0rmz (via Flickr); me (via Post-It note).

Squid's Daily Rhythms Are Controlled by Glowing Symbiotic Bacteria

At nightfall, the Hawaiian bobtail squid digs itself out of the sand and rises into the ocean water like a spaceship taking off. It switches on its cloaking device: glowing bacteria inside its body light up, disguising the squid's silhouette against the moonlight for any predators swimming below. As sleek a vehicle as it appears, though, the bobtail may not totally outrank its microscopic crewmembers. The bacteria seem to power a clock inside the squid's body that can't function without them.

Hiding during the day and hunting at night in shallow Pacific waters, Euprymna scolopes clearly has a working circadian clock. Researchers had noticed, though, that the squid's light organ—the specialized pocket inside its body that houses its bacterial helpers—seemed to have a rhythm of its own. The Vibrio fischeri bacteria give off fluctuating amounts of light throughout the day, for one thing. And the bacteria have their own daily rhythm of gene expression (when various genes are turned on or off), explains Margaret McFall-Ngai, a microbiologist at the University of Wisconsin, Madison.

McFall-Ngai and her coauthors looked for genes linked to circadian rhythms within the squid. They found two types of "cry" genes, which are known to control internal clocks throughout the animal and plant kingdoms. One gene had a daily cycle of activity in the squid's head—which is what you'd expect, since animals' main circadian clocks are in our brains. Other clocks can be elsewhere in the body, though, and this is what researchers found with the second cry gene. It was cycling only within the light organ.

Baby squid, which hadn't yet collected bacterial friends in their light organs, didn't show the same cycling. So it seemed that the bacteria themselves were driving the daily rhythms in the light organ. When the researchers let squid fill their light organs with defective, non-glowing bacteria, the cry gene still didn't cycle properly. This suggested that the glow of the bacteria was the crucial ingredient.

To test this idea, the scientists shone a blue light on the squid holding defective bacteria. Now they expressed just as much cry as the original squid.

McFall-Ngai explains that cryptochromes, the proteins made by cry genes, respond to blue light. Based on the light signals the cryptochromes receive, they turn other genes on or off. Cryptochromes in the squid's head respond to light from the sun to drive its daily rhythms, as in other animals and plants. Those in its light organ, though, respond to the light of its glowing bacterial companions.

The role of the bacterial clock isn't clear yet. "We don't know if the light organ rhythms control any other rhythms in the body," says McFall-Ngai. "But they certainly seem to be involved in controlling the rhythms of the organ itself." The squid controls the daily schedule of the bacteria, too: it jettisons most of its bacteria in the morning, and seems to keep them dimmed during the day by restricting their oxygen supply. At night, it gives the bacteria enough resources to glow at full strength—and that glow drives the clock within the light organ. "There seems to be a tit for tat," McFall-Ngai says. "The host and symbiont 'talk' to one another, controlling one another's biology."

The idea that bacteria can drive circadian rhythms inside their hosts is exciting to humans because we, too, are animals packed full of bacteria. Ours don't glow, but they do line our guts and participate in digesting our food. McFall-Ngai points out that scientists have found "profound circadian rhythms" within our gut tissues, both in their activity and in what genes they express.

Even though we're land-bound, non-glowing vertebrates, our bacteria could be powering circadian rhythms within our bodies just like the squid's. "We think it might be a very general phenomenon," McFall-Ngai says. Our microscopic passengers, that is, might be helping to steer the spaceship.

Heath-Heckman, E., Peyer, S., Whistler, C., Apicella, M., Goldman, W., & McFall-Ngai, M. (2013). Bacterial Bioluminescence Regulates Expression of a Host Cryptochrome Gene in the Squid-Vibrio Symbiosis mBio, 4 (2) DOI: 10.1128/mBio.00167-13

Image: Margaret McFall-Ngai

New Journal Celebrates Animal Stalking

Christmas arrived early this year for people who love animals carrying transmitters around. A new open-access journal called Animal Biotelemetry launched this week, and it promises to bring new tales of mind-blowing bird migrations and seals that study climate change (without exactly having volunteered for the job). Also, sharks.

Published by BioMed Central, the journal will include all kinds of research having to do with biological data gathered by instruments attached to animals. This is a field that's been expanding as the technologies themselves shrink. A few decades ago, scientists were limited to studying the movements of giant land animals such as bears or elk—because transmitters and battery packs were too bulky to comfortably attach to other creatures. Now, miniaturized electronics (aided by GPS satellites) mean that even lightweight birds can carry tracking devices.

Editor A. Peter Klimley describes the history of the field in an introduction to the journal. Klimley himself is a professor and shark guy at the University of California, Davis. His biography claims that he "is known to have held his breath while diving up to 100m deep in order to hand-tag hammerhead sharks with a dart gun." In case "biotelemetry" didn't sound exciting to you.

To mark the occasion, here are some earlier posts involving animals carrying transmitters around, since I am one of the aforementioned people who love them.

Monitoring from Space Shows Even This Giant Crab Can Navigate Better than You

Climate-Studying Seals Bring Back Happy News

This Penguin: An Unexpected Journey

Klimley, A. (2013). Why publish Animal Biotelemetry? Animal Biotelemetry, 1 (1) DOI: 10.1186/2050-3385-1-1

Image: by MEOP Norway North

Kids Learn Better When Teachers Wave Their Hands

Maybe it's no mistake that we talk about "grasping" new ideas. When we find our hands moving wildly as we try to explain something, maybe we shouldn't feel ridiculous. Research in math classrooms has found that kids learned better when a teacher used gestures—and their grip on the new material improved even more after the lesson ended.

Teachers who gesture more or less while they speak can have other differences too, of course: they might use different intonation or vocabulary, or have more or less energy. University of Iowa psychologist Susan Wagner Cook and her coauthors, though, were only interested in the effect of teachers' hand motions. To isolate this factor, they created a series of videos.

In the videos, aimed at elementary schoolers, a teacher taught a single scripted lesson. The subject of the lesson was equivalence, the idea that what's on one side of an "=" must be equal to the other side.

In one set of videos, the teacher used her hand to indicate "one side" and "the other side" of an equation. A second set of videos showed the same teacher reading the same script, but she kept her hands at her sides. The researchers made several recordings and chose the ones in which the teacher's intonation was the most consistent, ensuring that the only difference between the lessons was her hands.

The kids who watched the videos were 184 boys and girls from 22 classrooms in central Michigan schools. Most were in second or third grade, and a few were in fourth. The kids had taken a pretest to make sure they weren't already familiar with this mathematical idea.

Each classroom watched a videotaped lesson, either the one with hand gestures or the one without. Immediately afterward, they took a test with questions such as:
7 + 2 + 4 = 7 + __
Kids who had understood the lesson would answer "6."

A day later, the kids had a second set of test questions spring on them. First they answered the same type of questions that they had the day before. Then they saw a second set of questions designed to make them "transfer" the rules they'd learned to new situations. For second graders, this meant trickier addition problems such as:
6 + 4 + 2 = __ + 3
in which none of the numbers on the right side matched the left. Third and fourth graders had to transfer their new skills to multiplication problems such as:
5 x 2 x 3 = __ x 3

Kids who had seen the lesson with gestures did significantly better than the no-gesture kids on the first test. A day later, they again outperformed the hands-free group—and beat their own test scores from the day before. Their understanding of the lesson seemed to have gotten even better in the 24 intervening hours. (This wasn't true of kids who watched the hands-free lesson.) Finally, the gesture group did better on the test of transferred skills.

A couple factors could explain why students learned better from a gesturing teacher, the authors write. Hand movements might help them pay better attention to the teacher, for example. And seeing a repeated hand motion across different problems might reinforce how those problems are similar.

That doesn't answer the question of why students continued to improve over the next 24 hours. Susan Wagner Cook explains that shortly after we form new memories, those memories are stabilized or "consolidated" in our minds. Consolidation can make new memories even stronger.

"We do know that motor memory is often consolidated during sleep," Cook says. Seeing another person's hands moving may have built motor (movement) memories in kids' minds, as if they were pointing and waving their own hands. "One possibility is that memories encoded with gesture are more likely to be consolidated during sleep," Cook says. "We are trying to figure this out!"

Although being able to point to the two sides of an equation seems like a clear advantage in this particular lesson, Cook says the benefit of gesturing goes beyond arithmetic—or even math. Other studies have shown that hand motions help kids learn in a wide range of subjects.

What's new is the idea that gestures help in the future, not only the present. Cook points out that even though some kids learned the lesson just fine without gestures, they didn't show the same improvement over time that the other kids did. Instead of only clarifying, gestures may help kids grasp their new knowledge more tightly. (Please imagine a fist-closing gesture to drive home this idea.)

Image: sleepinyourhat (via Flickr)

Cook, S., Duffy, R., & Fenn, K. (2013). Consolidation and Transfer of Learning After Observing Hand Gesture Child Development DOI: 10.1111/cdev.12097

Why Fish Raise Foster Kids (and Give Up Their Own)

A fish swims along a sandy lake bottom, carrying one of its babies in its mouth. It approaches the nesting cave of another family of fish. With a furtive "ptooey," it leaves the baby behind for adoption. For certain fish, this seems to be a common scene: giving up your young and taking on others' may be the best way to ensure your offspring grow past snack size.

The fish in question is Neolamprologus caudopunctatus, a type of cichlid (pronounced like a compliment for someone's hat).* Just a couple of inches long, the diminutive fish lives only in East Africa's Lake Tanganyika. Males and females form monogamous pairs. They raise their young in burrows under rocks; carrying sand in their mouths, they pile it up around the rocks to build narrow entrances.

For the first 40 days or so in the lives of the young fish (called fry), both parents work to protect them from predators. They guard the nest and attack any other fish that come by looking for a meal. Cichlids can also protect their young by carrying them inside their mouths.

As the fry grow older and start swimming on their own, they may wander away from their parents' nests and into nearby ones. However, cichlids have also been spotted carrying young in their mouths and leaving them at other nests. Scientists at the Konrad Lorenz Institute of Ethology in Vienna set out to see how much of the baby swapping among N. caudopunctatus is intentional.

Researchers scuba dived down to the home of the cichlids, mapped the locations of their nests, and collected DNA samples. Back on land, like the crew of a daytime talk show for African lake bottoms, they analyzed the DNA to find out just how these fish were related.

Out of 32 nests, more than half held adopted fry, the authors report in Behavioral Ecology. Within nests that housed adopted fish, those outsiders made up anywhere from 10% to 77% of the nest.

The researchers took their DNA analysis a step further for a dozen adopted fry, hunting down their biological parents. They found that while some fry had been adopted from nearby nests, others were a very long way from home—as far as 40 meters or more. "It is virtually inconceivable that they swam there alone," says senior author Richard Wagner. The lake is packed with hungry predators. It would be, he says, "like a toddler walking across a busy city without mishap." It's more likely that parents deliberately carried these young fish in their mouths from one nest to the other.

There was another piece of evidence that adoptions happened on purpose. Adopted fish were on average larger (which is to say older) than non-adopted fish across the whole sample. But within each nest, the size difference wasn't significant. This suggests that when cichlid parents give up their young, they select nests with fry that are close in size to their own. Such a strategy might make the adopted fish less conspicuous to predators.

Parents who leave their fry at other nests may be hedging their bets, making sure that at least some of their offspring survive if their own nest is wiped out by a predator. As for adoptive parents, they could just kick out the freeloading fry. But keeping adopted fish around means that when predators attack, there's a smaller chance of your own offspring ending up in another fish's mouth.

"Our paper adds evidence that adoption is an adaptive strategy," Wagner says, rather than simply the result of wandering babies. We humans aren't the only animals that regularly choose to raise others' young. One hopes, though, that human foster parents aren't in it for the reduced predation.

Schaedelin, F., van Dongen, W., & Wagner, R. (2012). Nonrandom brood mixing suggests adoption in a colonial cichlid Behavioral Ecology, 24 (2), 540-546 DOI: 10.1093/beheco/ars195

Image: N. caudopunctatus by Varmer (via Flickr)

*"Sick lid!"

NOTE: It's been pointed out to me by an astute reader (my mother) that the hat compliment could also be "chic lid." Fair point, Mom.