Expanding the umwelt

The concept of the umwelt is a little mind-boggling.

It's defined as "the world as perceived by a particular organism."  In superficial terms we know that a dog must perceive life differently than we do.  For example, we know their senses of smell are a lot more keen than ours are, but the magnitude is staggering.  They have about fifty times the number of olfactory receptors than we do (three hundred million as compared to six million), so their world must be as vivid a tapestry of smells as ours is a tapestry of sights and sounds.

While it might be possible to imagine what it's like to have an enhanced sense, what about having a sense we lack entirely?  A number of animals, including sharks, platypuses, and knifefish, have an ability to sense electric fields, so the voltage change in the water around them registers as a sensory input, just as light or sound or taste does for us.  They use this sense to locate prey, because the neuromuscular systems of the animals they're hunting create a weak electrical discharge, which all of these animals can "see."

In the amazing 2015 TED Talk "Can We Create New Senses for Humans?",  neuroscientist David Eagleman explores what it would be like to expand our umwelt.  He has designed a vest, to be worn against the skin, that has a series of motors that create tiny vibrations.  The vest's input can be whatever you want; in one demonstration, sounds picked up by a microphone are the input used to create a pattern of vibrations on the chest and back.  With only a couple of days of training, a profoundly deaf individual was able to translate the patterns into a perception of the sounds, and correctly identify spoken words.

His brain had basically taken a different peripheral input device and plugged it into the auditory cortex!

Experiments with other "peripherals" have included using a pattern of weak electrical tingles transmitted onto the tongue via a horseshoe-shaped flat piece of metal to allow blind people to navigate around objects while walking, and even get good enough with it that they can throw an object into a basket.  One of Eagleman's experiments with the vest trained people using an input from an unidentified source -- all they did was press one of a pair of buttons and found out if their choice was right:

A subject is feeling a real-time streaming feed from the Net of data for five seconds.  Then, two buttons appear, and he has to make a choice.  He doesn't know what's going on.  He makes a choice, and he gets feedback after one second.  Now, here's the thing: the subject has no idea what all the patterns mean, but we're seeing if he gets better at figuring out which button to press.  He doesn't know that what we're feeding is real-time data from the stock market, and he's making buy and sell decisions.  And the feedback is telling him whether he did the right thing or not.  And what we're seeing is, can we expand the human umwelt so that he comes to have, after several weeks, a direct perceptual experience of the economic movements of the planet.

The wildest thing is that the peripheral you add doesn't have to be input; it can be output.  Two different papers, both in the journal Science, have shown that you can add an output device, and like with the inputs -- all it takes is a little training.

In the first, "A Brain-Computer Interface that Evokes Tactile Sensations Improves Robotic Arm Control," test subjects have a computer interface device implanted into their brain, which then translates thoughts into movements of a robotic arm, analogous to what an intact neuromuscular system is doing to our actual arms.  This has been doable for a while, but the advance in this study is that the robotic arm has sensors that provide feedback, again just like our own systems do when working properly.  Think about picking up a coffee cup; you adjust the pressure and position of your grip because you're constantly getting feedback, like the temperature of the cup, the weight and balance, whether your fingers are hanging on well or slipping, and so forth.

Here, the feedback provided by the sensors on the robotic arm cut in half the time taken for doing an action without mishap!  The brain once again picked up very quickly how to use the additional information to make the output go more smoothly.

In the second, people were trained with a "third thumb" -- an artificial extra digit strapped to the hand on the pinky-finger side.  It's controlled by pressure sensors under the toes, so you're using your feet to move something attached to your hand while simultaneously using your brain to control your other hand movements, which seems impossibly complicated.  But within a day, test subjects could perform tasks like building a tower from wooden blocks using the augmented hand... even when distracted or blindfolded!

Study author Paulina Kieliba, of University College - London's Institute of Cognitive Neuroscience, said, "Body augmentation could one day be valuable to society in numerous ways, such as enabling a surgeon to get by without an assistant, or a factory worker to work more efficiently.  This line of work could revolutionize the concept of prosthetics, and it could help someone who permanently or temporarily can only use one hand, to do everything with that hand.  But to get there, we need to continue researching the complicated, interdisciplinary questions of how these devices interact with our brains."

Co-author Tamar Makin summed it up: "Evolution hasn’t prepared us to use an extra body part, and we have found that to extend our abilities in new and unexpected ways, the brain adapts the representation of the biological body."

I think what amazes me most about all this is the flexibility of the brain.  The fact that it can adjust to such radical changes in inputs and outputs is phenomenal.  Me, I'm waiting for something like Tony Stark's suit in Iron Man.  That'd not only allow me to fight crime, but it'd make yard chores a hell of a lot easier.

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Too many people think of chemistry as being arcane and difficult formulas and laws and symbols, and lose sight of the amazing reality it describes.  My younger son, who is the master glassblower for the chemistry department at the University of Houston, was telling me about what he's learned about the chemistry of glass -- why it it's transparent, why different formulations have different properties, what causes glass to have the colors it does, or no color at all -- and I was astonished at not only the complexity, but how incredibly cool it is.

The world is filled with such coolness, and it's kind of sad how little we usually notice it.  Colors and shapes and patterns abound, and while some of them are still mysterious, there are others that can be explained in terms of the behavior of the constituent atoms and molecules.  This is the topic of the phenomenal new book The Beauty of Chemistry: Art, Wonder, and Science by Philip Ball and photographers Wenting Zhu and Yan Liang, which looks at the chemistry of the familiar, and illustrates the science with photographs of astonishing beauty.

Whether you're an aficionado of science or simply someone who is curious about the world around you, The Beauty of Chemistry is a book you will find fascinating.  You'll learn a bit about the chemistry of everything from snowflakes to champagne -- and be entranced by the sheer beauty of the ordinary.

[Note: if you purchase this book from the image/link below, part of the proceeds goes to support Skeptophilia!]

The return of the senses

The news has been pretty uniformly dismal lately.

I don't even have to list all the ways.  We've all been inundated by the headlines, not to mention how these developments have changed our lives, and it's becoming increasingly clear those changes aren't going away soon.  It's easy to get discouraged, to decide that everything is bleak and hopeless.

So today, I want to look at a new development that should make you feel at least a little better about what humanity can accomplish -- in this case, for people who have been through the devastating experience of losing a limb.

A high school friend of mine was involved in a terrible accident on his family farm and ended up losing both of his arms from the elbow down.  He was fitted with prosthetic arms, and after recovering managed amazingly well -- his courage and fortitude through this ordeal was something that inspired our entire school, and still inspires me to this day.  But his prostheses were no real replacements for lower arms and hands, and there was (and is) a lot he could not do.

Those limitations might soon be a thing of the past.

A collaboration between Chalmers University of Technology, Sahlgrenska University Hospital, the University of Gothenburg, and Integrum AB (a Swedish medical technology firm), the Medical University of Vienna, and the Massachusetts Institute of Technology has produced prosthetic arms for three amputees in Sweden that interface directly with the user's nerves, muscles, and skeletons.  Not only does this mean that the patient has much improved fine motor control over the prosthetic hand, but the nerve connection runs both ways, not only delivering output to control what the hand does, but relaying input received by the hand back to the brain.

Put simply: this prosthesis has a sense of touch.

"Our study shows that a prosthetic hand, attached to the bone and controlled by electrodes implanted in nerves and muscles, can operate much more precisely than conventional prosthetic hands," said Max Ortiz Catalan, who headed the research and was lead author on the paper describing it that appeared last week in the New England Journal of Medicine, in an interview with Science Daily.  "We further improved the use of the prosthesis by integrating tactile sensory feedback that the patients use to mediate how hard to grab or squeeze an object.  Over time, the ability of the patients to discern smaller changes in the intensity of sensations has improved."

The new prostheses, as amazing as they are, are just the first step.  "Currently, the sensors are not the obstacle for restoring sensation," said Ortiz Catalan.  "The challenge is creating neural interfaces that can seamlessly transmit large amounts of artificially collected information to the nervous system, in a way that the user can experience sensations naturally and effortlessly."

It's kind of amazing how fluid the human brain can be.  Neuroscientist David Eagleman, in his brilliant talk "Can We Create New Senses for Humans?", describes our sensory organs as being like the peripherals in a computer system -- and explains how quickly the brain can learn to obtain the same information from a different peripheral.  Some of his examples:

• blind people using echolocation -- clicks -- to create a "soundscape" and navigate their surroundings
• in a separate experiment, the blind using a head-mounted camera connected by an electrical lead to a flat, horseshoe-shaped piece of metal resting on the tongue -- the camera translates what it "sees" into a pattern of tiny voltage changes in the piece of metal, which the brain converts to rudimentary visual images
• the hearing impaired using a vibrating vest hooked up to a microphone to learn to "hear" through the vibrations on their skin

For me, the most stunning thing about these examples is that the brain learns to reinterpret the signals coming from the "peripheral" -- in the first example, sounds activate the visual cortex; in the second, touch stimuli activate the visual cortex; in the third, touch stimuli activate the auditory cortex.  All neural signals are the same; the brain simply decides how to interpret them.  You literally are seeing with your ears, seeing with your tongue, or hearing with your skin.

Here, though, the peripheral really is a peripheral, i.e., a machine.  You're not co-opting one of your pre-existing senses for a different purpose; you're hooking in an external apparatus to your brain, receiving input from an array of computerized sensors.  You may have been reminded, as I was, of Luke Skywalker:

It's a phenomenal improvement over previous prostheses, that were moved by muscle contractions in the arm it was attached to; here, the prosthesis is not only mind-controlled, it sends information back to the brain about what it's touching, giving the wearer back at least the beginnings of a sense of touch.

"Right now, patients in Sweden are participating in the clinical validation of this new prosthetic technology for arm amputation," said Ortiz Catalan.  "We expect this system to become available outside Sweden within a couple of years, and we are also making considerable progress with a similar technology for leg prostheses, which we plan to implant in a first patient later this year."

So the news these days isn't all bad, even if you have to dig a bit to find the heartening parts.  Regardless of what's happening now, I remain an optimist about human compassion and human potential.  I'm reminded of the final lines of the beautiful poem "Desiderata" by Max Ehrmann: "With all its sham, drudgery and broken dreams, it is still a beautiful world.  Be cheerful.  Strive to be happy."

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This week's Skeptophilia book recommendation is about a phenomenal achievement; the breathtaking mission New Horizons that gave us our first close-up views of the distant, frozen world of Pluto.

In Alan Stern and David Grinspoon's Chasing New Horizons: Inside the Epic First Mission to Pluto, you follow the lives of the men and women who made this achievement possible, flying nearly five billion kilometers to something that can only be called pinpoint accuracy, then zinging by its target at fifty thousand kilometers per hour while sending back 6.25 gigabytes of data and images to NASA.

The spacecraft still isn't done -- it's currently soaring outward into the Oort Cloud, the vast, diffuse cloud of comets and asteroids that surrounds our Solar System.  What it will see out there and send back to us here on Earth can only be imagined.

The story of how this was accomplished makes for fascinating reading.   If you are interested in astronomy, it's a must-read.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

Animal magnetism

In my introductory neuroscience class, I always began the unit on our sensory systems by asking students how many senses they think we have.

The standard answer, of course, is "five."  There were always a few wishful thinkers who like the idea of psychic abilities and answered six.  They were uniformly blown away when I told them that depending on how you count them, it's at least twenty.

Don't believe me?  There are three in the ears (hearing, proprioception/balance, and pressure equalization).  The tongue has separate, distinct chemoreceptors for at least five different taste categories -- sour, sweet, salty, bitter, and savory.  For convenience we'll call the sense of smell one, because we don't even know how many different kinds of olfactory receptors we have.  The eyes are not only responsible for image reception, but also perception of depth and adjustments for light intensity.  You've got six in your skin -- touch, pain, pressure, heat, cold, and stretch.  Your brain has chemical sensors that keep track of your blood pH and stimulate your breathing rate to speed up or slow down to accommodate (in general, breathing faster dumps carbon dioxide and makes your blood pH rise; slower breathing makes you retain carbon dioxide and drops your blood pH).  The kidneys have sensors not only for blood pH but for the salt/water balance, concentrating or diluting your urine to keep your blood's osmotic balance correct.

And those are just the most obvious ones.

In reality, your body is a finely-tuned environmental sensor, constantly detecting and making adjustments to your internal state to accommodate for the external conditions.  It works admirably well most of the time, even though there are some stimuli out there detectible by other animal species that we are completely unaware of.

The one that jumps to mind first is the range of light frequencies the eyes can detect.  We can only pick up a tiny slice of the entire electromagnetic spectrum, the familiar red-orange-yellow-green-blue-indigo-violet of the rainbow.  Many insects can see in the ultraviolet region, picking up light waves completely invisible to us; this is why a good many flowers that seem to be a single color to us have wild patterns if photographed with a UV-sensitive camera.  Mosquitoes can pick up infrared light, meaning they see the world through heat-sensing goggles -- with the unfortunate result that they can find us with ease in the pitch dark.  (They can also smell us, apparently, possibly explaining why some people are so attractive to the little bastards.)

How a bee sees a flower of Potentilla reptans that looks solid yellow to us [Image licensed under the Creative Commons Wiedehopf20, Flower in UV light Potentilla reptans, CC BY-SA 4.0]

Sharks can pick up shifts in the underwater electric field, one way they find their prey -- muscle contractions run on electrical signals.  So, oddly enough, can platypuses, using electric sensors in their weird rubbery bill.  Many species of migratory birds are sensitive to magnetic fields, using magnetite crystals in their brains as a natural compass -- and, some scientists think, not only using them to figure out which direction is north, but using the declination (angle it tips up or down with respect to horizontal) to figure out the latitude, as the Earth's magnetic field lines become more and more vertical the closer you get to the poles.

This last one is a sense humans might actually share.  There have been anecdotal accounts for years of some people being sensitive to magnetic fields, but there hasn't been any hard evidence of it.  Now, a paper in eNeuro describes an experiment that shows the human brain has sensitivity to magnetic fields -- even if the owner of the brain may not be aware of it on a conscious level.

In "Transduction of the Geomagnetic Field as Evidenced from alpha-Band Activity in the Human Brain," by a team led by Connie Wang of the California Institute of Technology, we read about a clever set-up to see what was going on in people's heads when they were subjected to a fluctuating magnetic field.

The thought was, if there is anything at all to the anecdote, it should be detectible by an electroencephalogram.  "Our approach was to focus on brainwave activity alone," said study co-author Joseph Kirschvink (also of CIT) in an interview with Gizmodo.  "If the brain is not responding to the magnetic field, then there is no way that the magnetic field can influence someone’s behavior.  The brain must first perceive something in order to act on it—there is no such thing as ‘extra-sensory perception.’  What we have shown is this is a proper sensory system in humans, just like it is in many animals."

Test subjects were placed in a Faraday cage, a web of conductive material that blocks electromagnetic fields, to shut out anything coming from the Earth's magnetism.  Then, an array of Merritt coils were activated to alter the magnetic field within the cage.  The subjects were asked if they detected anything -- and at the same time, the EEG machine kept track of what was going on inside their skulls.

The results are fascinating.  The effect of the magnetic field shifts on the alpha waves was dramatic; you don't need a class in reading EEGs to see it.  What was equally interesting is that none of the test subjects reported being aware of any changes.  So even though there's a dramatic change in the brain waves, whatever effect that's having, if any, is happening on a completely subconscious level.

But it does mean the anecdotal stories about people's sensitivity to magnetic fields have at least a possible explanation.  It still doesn't mean those anecdotes are reliable -- that would take test subjects who were able to report a detectible change when the magnetic field shifted the wave pattern in their brains -- but it's a step in the right direction.

"Magnetoreception is a normal sensory system in animals, just like vision, hearing, touch, taste, smell, gravity, temperature, and many others," Kirschvink said.  "All of these systems have specific cells that detect the photon, sound wave, or whatever, and send signals from them to the brain, as does a microphone or video camera connected to a computer.  But without the software in the computer, the microphone or video camera will not work.  We are saying that human neurophysiology evolved with a magnetometer—most likely based on magnetite—and the brain has extensive software to process the signals."

So this might be another one to add to the list of human senses, at least for some of us.  Whatever the results, it's certain that we're more finely-tuned to our environment than we realize -- and sensitive to stimuli to which we've always thought we were wholly insensate.

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This week's Skeptophilia book recommendation of the week is a classic -- Martin Gardner's wonderful Did Adam and Eve Have Navels?

Gardner was a polymath of stupendous proportions, a mathematician, skeptic, and long-time writer of Scientific American's monthly feature "Mathematical Games."  He gained a wonderful reputation not only as a puzzle-maker but as a debunker of pseudoscience, and in this week's book he takes on some deserving targets -- numerology, UFOs, "alternative medicine," reflexology, and a host of others.

Gardner's prose is light, lucid, and often funny, but he skewers charlatans with the sharpness of a rapier.  His book is a must-read for anyone who wants to work toward a cure for gullibility -- a cure that is desperately needed these days.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

How plants see the world

The final project in my AP Biology class was to design a piece of original research, carry out an experiment, and report on the results.  I was amazed at the creative ideas students came up with, and the elegance of their methods for finding an answer -- methods that were limited by considerations of budget, space, and time.

One of the best ones I recall came out of a discussion in class when we were studying botany.  I was telling the students about statoliths, small, dense particles in the cells of plants near the tips of roots and stems, that sink to the bottom of the cell and tell the plant what direction is up.  This detection of the pull of gravity allows for gravitropism, in which the roots grow downward and the stems upward, even in the absence of light.

This sense gets taken away in zero-g conditions, as on the International Space Station.  Experiments there have shown that without an apparent pull of gravity, seeds will sprout and the roots and stems grow in whatever direction the seed is oriented -- even if that means the roots will grow upward and the stems downward.

A student asked, "What would happen if you increased the pull of gravity?  In a spaceship floating in the atmosphere of Jupiter, for example?"

I had no idea, and I told him so.  Good question, but to my knowledge it hadn't ever been tested.

So when the end of the year came, that student decided to find out.

Since a trip to Jupiter was kind of out of the question, he designed an apparatus to simulate higher-gravity conditions.  He got an old ceiling fan motor and some lengths of PVC pipe, and built himself an electronic whirligig.  He then grew sunflower seeds in two-liter soda bottles hanging on the ends of the vanes -- attached the bottles and then spun the hell out of them.  Knowing the rotational speed of the whirligig and the radius of the vanes, he could calculate the centripetal force being exerted on the bottles, and thus the increase in apparent gravitational pull.

And when he opened up the bottles, he found something extraordinary.  The higher the average gravitational pull the seedlings experienced, the shorter they were, and the thicker the stems.  Up to the limit of his whirligig's speed, it was a nearly linear relationship -- higher pull = shorter, stouter seedlings.

So somehow, plants can not only detect the direction of the pull of gravity, but its strength.

We're just starting to understand how plants sense the world, and what sorts of responses they are capable of.  A paper last week in Current Biology, describing research conducted at the University of Helsinki, unlocked a piece of what might have been going on with my student's spinning sunflowers.  The research team, led by botanist Juan Alonso-Serra, found that birch trees whose branches are weighted -- simulating a higher-mass crown -- increase the rate of the radial growth of their trunks in order to better support the higher weight.  Better still, they found that the gene called ELIMÄKI (EKI) is critical to this response; plants with a defective EKI locus were not able to do this growth-rate compensation, and eventually collapsed.

The authors write:

Our results highlight a regulatory circuit by which weight in tree trunks mechanically stimulates cambial growth.  The ELIMÄKI locus participates in this circuit, as shown by its requirement at various levels, from weight-induced growth response to the proper control of gene expression related to touch-induced mechanosensing.  The circuit facilitates the local acquisition of the biomechanical characteristics of xylem in the correct spatiotemporal manner, which systemically leads to a correct vertical proprioception response.  It remains to be studied how weight- and development-derived forces are sensed and transduced into radial growth, but our results indicate a critical role for a degree of lateral stem movement.  Similarly, it remains to be studied whether the ELIMÄKI locus contributes directly to the sensing of the proprioceptive signal or whether it is only part of its response.  Our results provide a mechanism through which the critical height:diameter ratio implied by the mechanical theory of tree evolution can be achieved.

Which is pretty amazing.  My long-ago student's research was prescient -- and now we have a possible genetic mechanism by which this response is modulated.  (Note, however, that Alonso-Serra's team still had no model for how plants are sensing the higher weight.)

Plants are aware of their surroundings in ways that are only now being understood.  One of the more mysterious responses, for which I have still heard no particularly convincing explanations, is crown shyness -- the tendency in some tree species to avoid coming near the branches of other trees, leaving "lanes" of open sky when viewed from below.

A grove of the Malaysian dipterocarp Dryobalanops aromatica, showing crown shyness [Image is in the Public Domain]

Why the usual approach -- growing taller and broader than your neighbor, so as to have better access to light (and as a side benefit, discouraging competition from the individuals around you) -- doesn't apply here, I don't know.  Two possible explanations are that having your branches not touch your neighbors' results in less chance of mechanical damage from the wind, and also provides less of a pathway for herbivores to get to you from nearby trees.

But it's hard for me to see how such minor benefits would result in such a striking response, which apparently has evolved more than once in only distantly-related species.

Also not fully understood is the phenomenon of photoperiodism, the way many plants time when to flower based on the relative lengths of the day and night.  There are a few suggestive experiments that the critical thing is the length of the night rather than the day -- breaking up the dark period by even a short flash of light disrupts the response, whereas a short dark period in the middle of the day has no effect.  Light in the red region of the spectrum has the strongest ability to disrupt this response, probably because a protein involved in the response (phytochrome) has its highest sensitivity to red light.  Some plants are extraordinarily sensitive, responding to changes in the day/night length of only a few minutes.

But exactly how they're accomplishing all of this is only partially understood.

So if we're just beginning to figure out how our own senses work, we've barely scratched the surface with the sensory apparatus of plants.  What's certain is they're not the mostly-inert little lumps we once thought, passively absorbing sunlight, otherwise unaware of their surroundings.  Plants are capable of sophisticated sensing and response -- whether to day/night length, the proximity of neighbors, weights on the branches -- or being spun around in a cobbled-together electric whirligig.

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This week's Skeptophilia book of the week is both intriguing and sobering: Eric Cline's 1177 B.C.: The Year Civilization Collapsed.

The year in the title is the peak of a period of instability and warfare that effectively ended the Bronze Age.  In the end, eight of the major civilizations that had pretty much run Eastern Europe, North Africa, and the Middle East -- the Canaanites, Cypriots, Assyrians, Egyptians, Babylonians, Minoans, Myceneans, and Hittites -- all collapsed more or less simultaneously.

Cline attributes this to a perfect storm of bad conditions, including famine, drought, plague, conflict within the ruling clans and between nations and their neighbors, and a determination by the people in charge to keep doing things the way they'd always done them despite the changing circumstances.  The result: a period of chaos and strife that destroyed all eight civilizations.  The survivors, in the decades following, rebuilt new nation-states from the ruins of the previous ones, but the old order was gone forever.

It's impossible not to compare the events Cline describes with what is going on in the modern world -- making me think more than once while reading this book that it was half history, half cautionary tale.  There is no reason to believe that sort of collapse couldn't happen again.

After all, the ruling class of all eight ancient civilizations also thought they were invulnerable.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

The smell of time passing

We once owned a very peculiar border collie named Doolin.  Although from what I've heard, saying "very peculiar" in the same breath as "border collie" is kind of redundant.  The breed has a reputation for being extremely intelligent, hyperactive, job-oriented, and more than a little neurotic, and Doolin fit the bill in all respects.

As far as the "intelligent" part, she's the dog who learned to open the slide bolts on our fence by watching us do it only two or three times.  I wouldn't have believed it unless I'd seen it with my own eyes.  She also took her job very seriously, and by "job" I mean "life."  She had a passion for catching frisbees, but I always got the impression that it wasn't because it was fun.  It was because the Russian judge had only given her a 9.4 on the previous catch and she was determined to improve her score.

There were ways in which her intelligence was almost eerie at times.  I was away from home one time and called Carol to say hi, and apparently Doolin looked at her with question marks in her eyes.  Carol said, "Doolin, it's Daddy!"  Doolin responded by becoming extremely excited and running around the house looking in all of the likely spots -- my office, the recliner, the workshop -- as well as some somewhat less likely places like under the bed.  When the search was unsuccessful, apparently she seemed extremely worried for the rest of the evening.

Not that this was all that different from her usual expression.

One thing that always puzzled us, though, was her ability to sense when we were about to get home.  Doolin would routinely go to the door and stand there on guard before Carol's car pulled into the driveway.  She did the same thing, I heard, when I was about to arrive.  In each case, there was no obvious cue that she could have relied on; we live on a fairly well-traveled stretch of rural highway and even if she heard our cars in the distance, I can't imagine they sound that different from any of the other hundreds of cars that pass by daily.  And my arrival time, especially, varied considerably from day to day, because of after-school commitments.  How, then, did she figure out we were about to get home -- or was it just dart-thrower's bias again, and we were noticing the times she got it right and ignoring all the times she didn't?

According to Alexandra Horowitz, a professor of psychology at Barnard University, there's actually something to this observation.  There are hundreds of anecdotal accounts of the same kind of behavior, enough that (although there hasn't been much in the way of a systematic study) there's almost certainly a reason behind it other than chance.  Horowitz considered the well-documented ability of dogs to follow a scent trail the right direction by sensing where the signal was weakest -- presumably the oldest part of the trail -- and heading toward where it was stronger.  The difference in intensity is minuscule, especially given that to go the right direction the dog can't directly compare the scent right here to the scent a half a kilometer away, but has to compare the scent here to the scent a couple of meters away.

What Horowitz wondered is if dogs are using scent intensity as a kind of clock -- the diminishment of a person's scent signal after they leave the house gives the dog a way of knowing how much time has elapsed.  This makes more sense than any other explanation I've heard, which include (no lie) that dogs are psychic and are telepathically sensing your approach.  Biological clocks of all kinds are only now being investigated and understood, including how they are entrained -- how the internal state is aligned to external cues.  (The most obvious examples of entrainment are the alignment of our sleep cycle to light/dark fluctuations, and seasonal behaviors in other animals like hibernation and migration in response to cues like decreasing day length.)

So it's possible that dogs are entraining this bit of their behavior using their phenomenally sensitive noses.  It'll be interesting to see what Horowitz does with her hypothesis; it's certainly worth testing.  Now, I need to wrap this up because Guinness's biological clock just went off and told him it was time to play ball.  Of course, that happens about fifty times a day, so there may not be anything particularly surprising there.

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This week's Skeptophilia book of the week is brand new; Brian Clegg's wonderful Dark Matter and Dark Energy: The Hidden 95% of the Universe.  In this book, Clegg outlines "the biggest puzzle science has ever faced" -- the evidence for the substances that provide the majority of the gravitational force holding the nearby universe together, while simultaneously making the universe as a whole fly apart -- and which has (thus far) completely resisted all attempts to ascertain its nature.

Clegg also gives us some of the cutting-edge explanations physicists are now proposing, and the experiments that are being done to test them.  The science is sure to change quickly -- every week we seem to hear about new data providing information on the dark 95% of what's around us -- but if you want the most recently-crafted lens on the subject, this is it.

[Note: if you purchase this book from the image/link below, part of the proceeds goes to support Skeptophilia!]

Ignoring the unimportant

Before I get into the subject of today's post, I want all of you to watch this two-minute video, entitled "Whodunnit?"

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How many of you were successful?  I know I wasn't.  I've watched it since about a dozen times, usually in the context of my neuroscience class when we were studying perception, and even knowing what was going on I still didn't see it.  (Yes, I'm being deliberately oblique because there are probably some of you who haven't watched the video.  *stern glare*)

This comes up because of some recent research that appeared in Nature Communications about why it is we get tricked so easily, or (which amounts to the same thing) miss something happening right in front of our eyes.  In "Spatial Suppression Promotes Rapid Figure-Ground Segmentation of Moving Objects," a team made up of Duje Tadin, Woon Ju Park, Kevin C. Dieter, and Michael D. Melnick (of the University of Rochester) and Joseph S. Lappin and Randolph Blake (of Vanderbilt University) describe a fascinating experiment they conducted that shows how when we look at something, our brains are actively suppressing parts of it we've (subconsciously) decided are unimportant.

The authors write:

Segregation of objects from their backgrounds is one of vision’s most important tasks.  This essential step in visual processing, termed figure-ground segmentation, has fascinated neuroscientists and psychologists since the early days of Gestalt psychology.  Visual motion is an especially rich source of information for rapid, effective object segregation.  A stealthy animal cloaked by camouflage immediately loses its invisibility once it begins moving, just as does a friend you’re trying to spot, waving her arms amongst a bustling crowd at the arrival terminal of an airport.  While seemingly effortless, visual segregation of moving objects invokes a challenging problem that is ubiquitous across sensory and cognitive domains: balancing competing demands between processes that discriminate and those that integrate and generalize.  Figure-ground segmentation of moving objects, by definition, requires highlighting of local variations in velocity signals.  This, however, is in conflict with integrative processes necessitated by local motion signals that are often noisy and/or ambiguous.  Achieving an appropriate and adaptive balance between these two competing demands is a key requirement for efficient segregation of moving objects.

The most fascinating part of the research was that they found you can get better at doing this -- but only at the expense of getting worse at perceiving other things.  They tested people's ability to detect a small moving object against a moving background, and found most people were lousy at it.  After five weeks of training, though, they got better...

... but not because they'd gotten better at seeing the small moving object.  Tested by itself, that didn't change.  What changed was they got worse at seeing when the background was moving.  Their brains had decided the background's movement was unimportant, so they simply ignored it.

"In some sense, their brain discarded information it was able to process only five weeks ago," lead author Duje Tadin said in an interview in Quanta.  "Before attention gets to do its job, there’s already a lot of pruning of information.  For motion perception, that pruning has to happen automatically because it needs to be done very quickly."

The last thing a wildebeest ever ignores.  [Image licensed under the Creative Commons Nevit Dilmen, Lion Panthera leo in Tanzania 0670 Nevit, CC BY-SA 3.0]

All of this reinforces once again how generally inaccurate our sensory-integrative systems are.  Oh, they work well enough; they had to in order to be selected for evolutionarily.  But a gain of efficiency, and its subsequent gain in selective fitness, means ignoring as much (or more) than you're actually observing.  Which is why we so often find ourselves in situations where we and our friends relate a completely different version of events we both participated in -- and why, in fact, there are probably times we're both right, at least partly.  We're just remembering different pieces of what we saw and heard -- and misremembering other pieces different ways.

So "I know it happened that way, I saw it" is a big overstatement.  Think about that next time you hear about a court case where a defendant's fate depends on eyewitness testimony.  It may be the highest standard in a court of law -- but from a biological perspective, it's on pretty thin ice.

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This week's Skeptophilia book recommendation is by the team of Mark Carwardine and the brilliant author of The Hitchhiker's Guide to the Galaxy, the late Douglas Adams.  Called Last Chance to See, it's about a round-the-world trip the two took to see the last populations of some of the world's most severely endangered animals, including the Rodrigues Fruit Bat, the Mountain Gorilla, the Aye-Aye, and the Komodo Dragon.  It's fascinating, entertaining, and sad, as Adams and Carwardine take an unflinching look at the devastation being wrought on the world's ecosystems by humans.

But it should be required reading for anyone interested in ecology, the environment, and the animal kingdom. Lucid, often funny, always eye-opening, Last Chance to See will give you a lens into the plight of some of the world's rarest species -- before they're gone forever.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

In the mind's eye

I've always found Charles Bonnet syndrome fascinating, and it's not just because the disorder was named after a scientist with whom I share a last name.

Nota bene: Bonnet is definitely not a relative of mine.  He was Swiss, whereas my father's family comes from the French Alps.  Plus, my dad's family name was changed when his great-grandfather emigrated to the United States -- it was originally Ariey.  In that area of France in the 19th century, there were often many branches of families living in a region, and the different branches were distinguished by adding the name of the town they were from as a hyphenated suffix.  My ancestors were Ariey-Bonnet -- Ariey from the town of St. Bonnet -- but when they came over, the immigration officials couldn't handle hyphenated names, so they just dropped the hyphen and Bonnet became the last name.  Just as well.  I have a hard enough time getting people to spell Bonnet correctly, I can't imagine what a pain in the ass it'd be to try to get people to spell Ariey correctly.

But I digress.

Charles Bonnet syndrome is sometimes called having "visual release hallucinations."  It is most common in people with visual impairment, and an odd feature of the disorder is that the people who are seeing them know they're not real.  Most of the time, hallucinations of any sort are terrifying, but in CBS, the sufferer usually just learns not to worry about them.  "I know I'm seeing little elves in carriages rolling alongside me when I walk," one 86-year-old with CBS said.  "When you get used to it, it's actually sort of amusing."

CBS is most common in people with macular degeneration, the most common cause of visual loss in the elderly.  This disorder causes the death of cells in the macula, or the center of the retina (also called the fovea), resulting in holes in the visual field that make it difficult or impossible to drive, watch television, and read.  An estimated 40% of people with macular degeneration experience some level of Charles Bonnet syndrome, experiencing visual hallucinations from the simple (flashing lights) to the elaborate (a head of a brown-eyed lion staring at you).  And new research has begun to explain why partial visual loss can result in bizarre hallucinations.

[Image licensed under the Creative Commons William H. Majoros, Lion-1, CC BY-SA 3.0]

This week, a paper appeared in the journal Cell entitled, "Stimulus-Driven Cortical Hyperexcitability in Individuals with Charles Bonnet Hallucinations," by David R. Painter, Michael F. Dwyer, Marc R. Kampke, and Jason B. Mattingly, of the University of Queensland.  The researchers found persuasive evidence that the weird hallucinations in CBS occur because the loss of visual acuity in the middle of the retina triggers the peripheral parts of the retina (and the parts of the visual cortex they're connected to) to overreact -- to become, in the researchers' words, "hyperexcitable."  The authors write:

Throughout the lifespan, the cerebral cortex adapts its structure and function in response to changing sensory input.  Whilst such changes are typically adaptive, they can be maladaptive when they follow damage to the peripheral nervous system, including phantom limb pain and tinnitus. An intriguing example occurs in individuals with acquired ocular pathologies—most commonly age-related macular degeneration (MD)—who lose their foveal vision but retain intact acuity in the peripheral visual field.  Up to 40% of ocular pathology patients develop long-term hallucinations involving flashes of light, shapes, or geometric patterns and/or complex hallucinations, including faces, animals, or entire scenes, a condition known as Charles Bonnet Syndrome (CBS). 

Though CBS was first described over 250 years ago, the neural basis for the hallucinations remains unclear, with no satisfactory explanation as to why some individuals develop hallucinations, while many do not.  An influential but untested hypothesis for the visual hallucinations in CBS is that retinal deafferentation [loss of sensory information from one part of the body] causes hyperexcitability in early visual cortex.  To assess this, we investigated electrophysiological responses to peripheral visual field stimulation in MD patients with and without hallucinations and in matched controls without ocular pathology.  Participants performed a concurrent attention task within intact portions of their peripheral visual field, while ignoring flickering checkerboards that drove periodic electrophysiological responses.  CBS individuals showed strikingly elevated visual cortical responses to peripheral field stimulation compared with patients without hallucinations and controls, providing direct support for the hypothesis of visual cortical hyperexcitability in CBS.

What this highlights once again is how fragile our sensory-perceptive systems are.  Loss of input from one area is bad enough; but instead of it simply causing a missing chunk from the sensory field, it causes you to misinterpret the signals from the part of your sensory system that is still working.  

Hardly seems fair.

At least CBS sufferers know what they're seeing isn't real, and learn to live with elves and lions and flashing lights.  Much worse are disorders like hebephrenic schizophrenia, where people have visual or auditory hallucinations -- and can't tell them from reality.  How completely terrifying that must be!

It's fascinating, however, to compare how certain we are that what we're seeing is real, and the minor changes it takes to have us see something that's clearly not real.  Once again, "I saw it with my own eyes" is a poor guide -- whether or not we're seeing elves in carriages.

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In writing Apocalyptic Planet, science writer Craig Childs visited some of the Earth's most inhospitable places.  The Greenland Ice Cap.  A new lava flow in Hawaii.  Uncharted class-5 rapids in the Salween River of Tibet.  The westernmost tip of Alaska.  The lifeless "dune seas" of northern Mexico.  The salt pans in the Atacama Desert of Chile, where it hasn't rained in recorded history.

In each place, he not only uses lush, lyrical prose to describe his surroundings, but uses his experiences to reflect upon the history of the Earth.  How conditions like these -- glaciations, extreme drought, massive volcanic eruptions, meteorite collisions, catastrophic floods -- have triggered mass extinctions, reworking not only the physical face of the planet but the living things that dwell on it.  It's a disturbing read at times, not least because Childs's gift for vivid writing makes you feel like you're there, suffering what he suffered to research the book, but because we are almost certainly looking at the future.  His main tenet is that such cataclysms have happened many times before, and will happen again.

It's only a matter of time.

[If you purchase the book from Amazon using the image/link below, part of the proceeds goes to supporting Skeptophilia!]

Trompe l'oeil

I have a fascination for optical illusions.

Not only are they cool, they often point out some profound information about how we process sensory input.  Take the famous two-and-a-half pronged fork:

The problem here is that we're trying to interpret a two-dimensional drawing as if it were a three-dimensional object, and the two parts of the drawing aren't compatible under that interpretation.  Worse, when you try to force your brain to make sense of it -- following the drawing from the bottom left to the top right, and trying to figure out when the object goes from three prongs to two -- you fail utterly.

Neil deGrasse Tyson used optical illusions as an example of why we should be slow to accept eyewitness testimony.  "We all love optical illusions," he said.  "But that's not what they should call them.  They should call them 'brain failures.'  Because that's what they are.  A clever drawing, and your brain can't handle it."

(If you have some time, check out this cool compendium of optical illusions collected by Michael Bach, which is even more awesome because he took the time to explain why each one happens, at least where an explanation is known.)

It's even more disorienting when an illusion occurs because of two senses conflicting.  Which was the subject of a recent paper out of Caltech, "What You Saw Is What You Will Hear: Two New Illusions With Audiovisual Postdictive Effects," by Noelle R. B. Stiles, Monica Li, Carmel A. Levitan, Yukiyasu Kamitani, and Shinsuke Shimojo.  What they did is an elegant experiment to show two things -- how sound can interfere with visual processing, and how a stimulus can influence our perception of an event, even if the stimulus occurs after the event did!

Sounds like the future affecting the past, doesn't it?  It turns out the answer is both simpler and more humbling; it's another example of a brain failure.

Here's how they did the experiment.

In the first trial, they played a beep three times, 58 milliseconds apart.  The first and third beeps were accompanied by a flash of light.  Most people thought there were three flashes -- a middle one coincident with the second beep.

The second setup was, in a way, opposite to the first.  They showed three flashes of light, on the right, middle, and left of the computer screen.  Only the first and third were accompanied by a beep.  Almost everyone didn't see -- or, more accurately, didn't register -- the middle flash, and thought there were only two lights.

Sorry, I couldn't resist.

"The significance of this study is twofold," said study co-author Shinsuke Shimojo.  "First, it generalizes postdiction as a key process in perceptual processing for both a single sense and multiple senses.  Postdiction may sound mysterious, but it is not—one must consider how long it takes the brain to process earlier visual stimuli, during which time subsequent stimuli from a different sense can affect or modulate the first.  The second significance is that these illusions are among the very rare cases where sound affects vision, not vice versa, indicating dynamic aspects of neural processing that occur across space and time.  These new illusions will enable researchers to identify optimal parameters for multisensory integration, which is necessary for both the design of ideal sensory aids and optimal training for low-vision individuals."

All cool stuff, and more information about how the mysterious organ in our skull works.  Of course, this makes me wonder what we imagine we see because our brain anticipates that it will there, or perhaps miss because it anticipates that something out of of place shouldn't be there.  To end with another quote from Tyson: "Our brains are unreliable as signal-processing devices.  We're confident about what we see, hear, and remember, when in fact we should not be."

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This week's Skeptophilia book recommendation is from the brilliant essayist and polymath John McPhee, frequent contributor to the New Yorker.  I swear, he can make anything interesting; he did a book on citrus growers in Florida that's absolutely fascinating.  But even by his standards, his book The Control of Nature is fantastic.  He looks at times that humans have attempted to hold back the forces of nature -- the attempts to keep the Mississippi River from changing its path to what is now the Atchafalaya River, efforts in California to stop wildfires and mudslides, and a crazy -- and ultimately successful -- plan to save a harbor in Iceland from a volcanic eruption using ice-cold seawater to freeze the lava.

Anyone who has interest in the natural world should read this book -- but it's not just about the events themselves, it's about the people who participated in them.  McPhee is phenomenal at presenting the human side of his investigations, and their stories will stick with you a long time after you close the last page.

[If you purchase the book from Amazon using the image/link below, part of the proceeds goes to supporting Skeptophilia!]

In the blink of an eye

One of the things I love about science is how it provides answers to questions that are so ordinary that few of us appreciate how strange they are.

I remember how surprised I was when I first heard a question about our vision that had honestly never occurred to me.  You know how images jump around when you're filming with a hand-held videocamera?  Even steady-handed people make videos that are seriously nausea-inducing, and when the idea is to make it look like it's filmed by amateurs -- such as in the movie The Blair Witch Project -- the result looks like it was produced by strapping a camera to the head of a kangaroo on crack.

What's a little puzzling is why the world doesn't appear to jump around like that all the time.  I mean, think about it; if you walk down the hall holding a videocamera on your shoulder, and watch the video and compare it to the way the hall looked while you were walking, you'll see the image bouncing all over the place on the video, but won't have experienced that with your eyes.  Why is that?

The answer certainly isn't obvious.  One guess scientists have is that we stabilize the images we see, and compensate for small movements of our head, by using microsaccades -- tiny, involuntary, constant jitters of the eyes.  The thought is that those little back-and-forth movements allow your brain to smooth out the image, keeping us from seeing the world as jumping around every time we move.

Another question about visual perception that I had never thought about was the subject of some recent research out of New York University and the University Medical Center of Göttingen that was just published last week in Current Biology.  Why don't you have the perception of the world going dark for a moment when you blink?  After all, most of us blink about once every five seconds, and we don't have the sense of a strobe effect.  In fact, most of us are unaware of any change in perception whatsoever.

[Image licensed under the Creative Commons Mcorrens, Iris of the Human Eye, CC BY-SA 3.0]

By studying patients who had lesions in the cerebrum, and comparing them to patients with intact brains, the scientists were not only able to answer this question, but to pinpoint exactly where this phenomenon happens -- the dorsomedial prefrontal cortex, a part of the brain immediately behind the forehead.  What they found was that individuals with an intact dmPFC store a perceptual memory of what they've just seen, and use that to form the perception they're currently seeing, so the time during which there's no light falling on the retina -- when you blink -- doesn't even register.  On the other hand, a patient with a lesion in the dmPFC lost that ability, and didn't store immediate perceptual memories.  The result?  Every time she blinked, it was like a shutter closed on the world.

"We were able to show that the prefrontal cortex plays an important role in perception and in context-dependent behavior," said neuroscientist Caspar Schwiedrzik, who was lead author of the study.  "Our research shows that the medial prefrontal cortex calibrates current visual information with previously obtained information and thus enables us to perceive the world with more stability, even when we briefly close our eyes to blink...  This is not only true for blinking but also for higher cognitive functions.  Even when we see a facial expression, this information influences the perception of the expression on the next face that we look at."

All of which highlights that all of our perceptual and integrative processes are way more sophisticated than they seem at first.  It also indicates something that's a little scary; that what we're perceiving is partly what's really out there, and partly what our brain is telling us it thinks is out there.  Which is right more often than not, of course.  If that weren't true, natural selection would have finished us off a long time ago.  But that fraction of the times that it's wrong, it can create some seriously weird sensations -- or make us question things that we'd always taken for granted.

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This week's recommendation is a classic.

When I was a junior in college, I took a class called Seminar, which had a new focus/topic each semester.  That semester's course was a survey of the Book Gödel, Escher, Bach: An Eternal Golden Braid by Douglas Hofstadter.  Hofstadter does a masterful job of tying together three disparate realms -- number theory, the art of M. C. Escher, and the contrapuntal music of J. S. Bach.

It makes for a fascinating journey.  I'll warn you that the sections in the last third of the book that are about number theory and the work of mathematician Kurt Gödel get to be some rough going, and despite my pretty solid background in math, I found them a struggle to understand in places.  But the difficulties are well worth it.  Pick up a copy of what my classmates and I came to refer to lovingly as GEB, and fasten your seatbelt for a hell of a ride.

[If you purchase the book from Amazon using the image/link below, part of the proceeds goes to supporting Skeptophilia!]