Twisted faces

One of the most terrifying episodes The X Files ever did was called "Folie à Deux."  In the opening scene, a man sees his boss not as a human but as a hideous-looking insectile alien who is, one by one, turning the workers in the company into undead zombies.

The worst part is that he's the only one who sees all of this.  Everyone else thinks everything is perfectly normal.

The episode captures in appropriately ghastly fashion the horror of psychosis -- the absolute conviction that the awful things you're experiencing are real despite everyone's reassurance that they're not.  In the show, of course, they are real; it's the people who aren't seeing it who are delusional.  But when this sort of thing happens in the real world, it is one of the scariest things I can imagine.  As I made the point in my neuroscience classes, your brain is taking the information it receives from your sensory organs and trying to assemble a picture of reality from those inputs; if something goes wrong, and the brain puts that information together incorrectly, that flawed picture becomes your reality.  At that point, there is no reliable way to distinguish reality from hallucination.

I was, unfortunately, reminded of that episode when a friend and loyal reader of Skeptophilia sent me a link yesterday to a story in NBC News Online about a man with prosopometamorphopsia, a (thank heaven) rare disorder that causes the patient's perception of human faces to go awry.  When he looks at another person, he sees their face as grotesquely stretched, with deep grooves in the forehead and cheeks.

Computer-generated images of what the patient describes seeing [Image credit: Antônio Mello, Dartmouth University]

Weirdly, it doesn't happen when he looks at a drawing or a photograph; only actual faces trigger the shift.  A moving face -- someone talking, for example -- accentuates the distortion.

Some people with prosopometamorphopsia (PMO) have it from birth; most, though, acquire it through physical damage to the brain, such as a stroke or traumatic brain injury.  The patient who was the first subject of this study shows up in MRI images with a lesion on the left side of his brain that is undoubtedly the origin of the distorted perception.  As far as the origin of that, he had a severe concussion in his forties (he's now 59), but also suffered from accidental carbon monoxide poisoning four months before the onset of symptoms.  Which of those is the root cause of the lesion, or if it's from something else entirely, is unknown.

At least now that he knows what's going on, he has been reassured that he's not going insane -- or worse, that he's seeing the world as it actually is, and like the man in "Folie à Deux," become convinced that he's the only one who does.  "My first thought was I woke up in a demon world," the patient told researchers, regarding how he felt when the symptoms started.  "I came so close to having myself institutionalized.  If I can help anybody from the trauma that I experienced with it and keep people from being institutionalized and put on drugs because of it, that’s my number-one goal."

I was immediately reminded of a superficially similar disorder called Charles Bonnet syndrome. (Nota bene: Charles Bonnet is no relation.  My French great-grandfather's name was changed upon arrival in the United States, so my last name shouldn't even be Bonnet.)  In this disorder, people with partial blindness, often from macular degeneration, start putting together the damaged and incomplete information their eyes are relaying to their brains in novel ways, causing what are called visual release hallucinations.  They can be complex -- one elderly woman saw what appeared to be tame lions strolling about in her house -- but there's no actual psychosis.  The people experiencing them, as with PMO, know (or can be convinced) that what they're seeing isn't real, which takes away a great deal of the anxiety, fear, and trauma of having hallucinations.

So at least that's one upside for PMO sufferers.  Still, it's got to be disorienting to look at the world around you and know for certain that what you're seeing isn't the way it actually is.  My eyesight isn't great, even with bifocals, but at least what I am seeing is real.  I'll take that over twisted faces and illusory lions any day.

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The electric landscape

In his remarkable TED Talk "Can We Create New Senses for Humans?," neuroscientist David Eagleman describes the concept of the umwelt -- the part of the available stimulus space sampled by a particular animal's senses.  A simple example is the thin slice of the electromagnetic spectrum our eyes are sensitive to -- the familiar ROYGBIV of the rainbow.  There's plenty of electromagnetic radiation outside of that slice; gamma rays, x-rays, ultraviolet light, infrared light, microwaves, and radio waves are all ordinary photons, just like visible light is.  It's just that our eyes aren't sensitive to those frequencies, so they're outside of our umwelt.

The umwelt also has to do with the relative weighting of senses; how big a part of our sensory world a particular experience constitutes.  Most humans have a sense of smell, but my dogs live in a far richer olfactory world than I do.  But even how those inputs are utilized -- i.e., what kind of information they provide for making sense of the world -- can vary greatly.  Bats and dolphins use hearing in much the same way as we use our eyes, creating "sonic landscapes" of the objects around them.  What's kind of amazing, though -- and one of the main points of Eagleman's talk -- is that humans can train their brains to use other "peripherals" (as he calls them) to learn about the world, such as blind people who have learned to navigate the space around them by making clicking noises and listening for echoes from nearby obstacles.

It's always been fascinating to me to consider how the world would look to a night-flying echolocating bat.  Do they "see" their world through their ears and auditory cortex?

The topic of how other animals perceive their worlds -- and how different it could be from what we experience -- comes up because of a paper this week in the journal Nature about how elephantnose fish (Gnathonemus petersii), which live in murky streams in west and central Africa where eyesight doesn't serve much purpose, develop their visual picture of the world (including locating prey) using electric fields.  And not only do they gain information by creating and sensing electrical signals, they enhance those pictures using the signals created by nearby members of their species, making them one of the only known animals that relies on collective signal production and sensing.

Gnathonemus petersii [Image is in the Public Domain]

"Think of these external signals as electric images of the objects that nearby electric fish automatically produce and beam to nearby fish at the speed of light," said Federico Pedraja of Columbia University, who headed the study. "Our work suggests that three fish in a group would each receive three different "electrical views" of the same scene at virtually the same time."

The elephantnose fish's capacity for working in groups is a little like humans out on a search at night with flashlights.  One person with one flashlight would have a small illuminated field of view, but if there were twenty people it would go much faster, not only because of greater manpower, but because each person wouldn't be restricted to what is revealed by only their own flashlight beam.  Just as with twenty different flashlights in the night rather than a single one, in the case of elephantnose fish, the electrical fields produced by their neighbors clarify the picture they all receive.

"In engineering it is common that groups of emitters and receivers work together to improve sensing, for example in sonar and radar," said Nathaniel Sawtell, who co-authored the study.  "We showed that something similar may be happening in groups of fish that sense their environment using electrical pulses.  These fish seem to 'see' much better in small groups...  [They] have some of the biggest brain-to-body mass ratios of any animal on the planet.  Perhaps these enormous brains are needed for rapid and highly sophisticated social sensing and collective behavior."

To return to my original point -- how would the world look to an elephantnose fish?  Surely nothing like what we see.  Some sort of topography of electrical field strength, perhaps, creating an image of the obstacles they have to maneuver around, the prey they seek, and the predators they need to avoid.  But really, there's no way to know.  We're all trapped within our own umwelt.  I can't even imagine what the world is like for my dogs, who are a great deal more similar to me than these fish are.

To perceive the world like another living being does, you'd not only have to come equipped with their sensory systems, but put the information together using their brains.  We can only speculate, with all the inevitable biases that come from being locked in our own ways of knowing.  But this study did at least give us a hint of how different the world could appear -- if we were odd little fish living in muddy African rivers.

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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 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 had to.

"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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Sounding off

Ever have the experience of getting into a car, closing the door, and accidentally shutting the seatbelt in the door?

What's interesting about this is that most of the time, we immediately realize it's happened, reopen the door, and pull the belt out.  It's barely even a conscious thought.  The sound is wrong, and that registers instantly.  We recognize when something "sounds off" about noises we're familiar with -- when latches don't seat properly, when the freezer door hasn't completely closed, even things like the difference between a batter's solid hit and a tip during a baseball game.

Turns out, scientists at New York University have just figured out that there's a brain structure that's devoted to that exact phenomenon.

A research team led by neuroscientist David Schneider trained mice to learn to associate a particular sound with pushing a lever for a treat.  After learning the sound, it became as habituated in their brains as our own expectation of what the car door closing is supposed to sound like.  If after that the tone was varied even a little, or the timing between the lever push and the sound was changed, a part of the mouse's brain began to fire rapidly.

The activated part of the brain is a cluster of neurons in the auditory cortex, but I think of it as the "What The Hell Just Happened?" module.

"We listen to the sounds our movements produce to determine whether or not we made a mistake," Schneider said.  "This is most obvious for a musician or when speaking, but our brains are actually doing this all the time, such as when a golfer listens for the sound of her club making contact with the ball.  Our brains are always registering whether a sound matches or deviates from expectations.  In our study, we discovered that the brain is able to make precise predictions about when a sound is supposed to happen and what it should sound like...  Because these were some of the same neurons that would have been active if the sound had actually been played, it was as if the brain was recalling a memory of the sound that it thought it was going to hear."

As a musician, I find myself wondering if this is why I had such a hard time unlearning my tendency to make a face when I hit a wrong note, when I first started performing on stage.  My bandmates said (rightly) that if it's not a real howler, most mistakes will just zoom right past the audience unnoticed -- unless the musician clues them in by wincing.  (My bandmate Kathy also added that if it is a real howler, just play it that way again the next time that bit of the tune comes around, and the audience will think it's a deliberate "blue note" and be really impressed about how avant-garde we are.) 

My band Crooked Sixpence, with whom I played for an awesome ten years -- l. to r., Kathy Selby (fiddle), me (flute), John Wobus (keyboard)

I found it a hard response to quell, though.  My awareness of having hit a wrong note was so instantaneous that it's almost like my ears are connected directly to my facial wince-muscles, bypassing my brain entirely.  I did eventually get better, both in the sense of making fewer mistakes and also responding less when I did hit a clam, but it definitely took a while for the flinch response to calm down.

It's interesting to speculate on why we have this sense, and evidently share it with other mammals.  The obvious explanation is that a spike of awareness about something sounding off could be a good clue to the presence of danger -- the time-honored trope in horror movies of one character saying something doesn't seem quite right.  (That character, however, is usually the first one to get eaten by the monster, so the response may be of dubious evolutionary utility, at least in horror movies.)

I find it endlessly fascinating how our brains have evolved independent little subunits for dealing with contingencies like this.  Our sensory processing systems are incredibly fine-tuned, and they can alert us to changes in our surroundings so quickly it hardly involves conscious thought.

Think about that the next time your car door doesn't close completely.

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The visual time machine

I don't know if you've ever considered what I'm about to describe; I know I had to have it pointed out to me.

Let's say you're walking down a long hallway, where there are other people, doorways, windows, pieces of art on the wall -- lots of stuff to look at.  As you walk, you move your head and your eyes to check out the surroundings, and also so you don't run into anyone.  Now, let's say that at the same time, you have a miniature videocamera attached to your forehead, so that it's recording the scene using the exact same perspective and movements as you.

Now, consider the difference between what you saw while walking, and what you'd see if you looked at the video of the same walk down the hall.

The recorded video would have incorporated every jolt from your feet striking the ground, every jerky movement of your head.  The visual field would bounce all over the place.  You know that show, Finding Bigfoot?  The one that's been going on for ten years, wherein despite the name, they have found exactly zero Bigfoots?  They're always showing video footage taken with hand-held video recorders, as the crew of the show run about in the woods excitedly not finding any Bigfoots, and those videos look like someone strapped the camera to a kangaroo on speed.  The movie The Blair Witch Project was filmed to look like it had been taken with a hand-held recorder, and they succeeded -- to the point that some people find it unwatchable, and end up feeling queasy or headachy from the scene being jostled around continuously.

The question is, why don't we see exactly the same thing?  Unless we're rattled way harder than usual -- like riding too fast in a car over a rutted and potholed road -- we have no visual sense of the fact that just like the video recorder, the scene we're looking at is jittering around continuously.

One possible explanation that has been given is microsaccades -- continuous minuscule back-and-forth jerks of the eyes that everyone has (but are so fast that you need a slowed-down video recording to see them).  It's possible that the brain uses these quick-but-tiny shifts in the visual field to smooth out the input and erase the sense that what you're seeing is bouncing around.

As an aside, there's another curious feature of microsaccades; they can be used to detect when someone's not paying attention.  I read about funny bit of research a few years ago, but unfortunately I can't find a link referencing it -- if anyone knows the source, please post a link in the comments.  The gist was that they took volunteers and attached head-mounted cameras to them, but the cameras weren't looking at the surroundings -- the lens was pointed backwards at the volunteers' eyes.  The instructions were that the volunteers were supposed to chat with the bartender, and not look around at anything or anyone else.  

Then, during the middle of the experiment, an attractive person of the volunteer's preferred gender walked in and sat down a few barstools over.  

The volunteers all did what they were told -- none of them turned and looked toward the eye candy parked only a few feet away.  But their microsaccades reacted big time.  The little jitters in the eye suddenly all were aimed in the same direction -- toward the hot-looking person near them.  It's like the brain is saying, "No, I can't look, I told the researchers I wouldn't," while the microsaccades are saying "LOOK AT THAT SEXY PERSON!  LOOK!  I KNOW YOU WANT TO!"

[Image licensed under the Creative Commons Laurinemily at English Wikipedia, Hazel-green eye 2, CC BY-SA 2.5]

In any case, some research came out last week, by Mauro Manassi (University of Aberdeen) and David Whitney (University of California - Berkeley), that suggests that there's another smoothing effect at work in addition to microsaccades.  What the researchers found was that there is a feature of our brain that does the same thing in time that the microsaccades do in space; they blur out little jolts by averaging the input.  In this case, your brain coalesces the images we've received during the last fifteen seconds, so any small vibrations get blended into a sense of a smooth, continuous visual field.

What the researchers did was to show volunteers a thirty-second video clip of a face that was slowly morphing in such a way that it appeared to change age.  The volunteers were then asked what age the individual was at the end of the clip.  Across the board, they underestimated the age of the face. On the other hand, given a still shot of the face as it was at the end resulted in fairly accurate assessment of the person's age.  But when watching the video, the answer they gave was consistently the apparent age of the individual not at the end, but the average over the previous fifteen seconds of the video.

The authors write:

In other words, the brain is like a time machine which keeps sending us back in time.  It’s like an app that consolidates our visual input every 15 seconds into one impression so that we can handle everyday life.  If our brains were always updating in real time, the world would feel like a chaotic place with constant fluctuations in light, shadow and movement.  We would feel like we were hallucinating all the time...  This idea... of mechanisms within the brain that continuously bias our visual perception towards our past visual experience is known as continuity fields.  Our visual system sometimes sacrifices accuracy for the sake of a smooth visual experience of the world around us.  This can explain why, for example, when watching a film we don’t notice subtle changes that occur over time, such as the difference between actors and their stunt doubles.

So once again, our sensory-perceptive systems (1) are way more complex than we thought, and (2) are recording the perceptions we have in such a way that they're not necessarily completely accurate, but the most useful.  "I saw it with my own eyes!" really doesn't mean very much.  As my neuroscience professor told us many years ago, "Your senses don't have to reflect reality; they just have to work well enough that you can find food, avoid being killed, and find a mate."

And if that means losing some visual accuracy in favor of the world not looking like hand-held video footage from Finding Bigfoot, I'm okay with that.

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It's obvious to regular readers of Skeptophilia that I'm fascinated with geology and paleontology.  That's why this week's book-of-the-week is brand new: Thomas Halliday's Otherlands: A Journey Through Extinct Worlds.

Halliday takes us to sixteen different bygone worlds -- each one represented by a fossil site, from our ancestral australopithecenes in what is now Tanzania to the Precambrian Ediacaran seas, filled with animals that are nothing short of bizarre.  (One, in fact, is so weird-looking it was christened Hallucigenia.)  Halliday doesn't just tell us about the fossils, though; he recreates in words what the place would have looked like back when those animals and plants were alive, giving a rich perspective on just how much the Earth has changed over its history -- and how fragile the web of life is.

It's a beautiful and eye-opening book -- if you love thinking about prehistory, you need a copy of Otherlands.

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

Color my world

Our ability to perceive color is, when you think about it, a peculiar thing.

First, there's the rather hackneyed question of whether we all see color the same way (exclusive, of course, of people who are colorblind).  The way the question is usually phrased goes something like, "How could we tell if when you look at something red, what you see what I call green, but you still call it red because that's what you've learned?"  In other words, if I were to take a look through your eyes and brain, would the colors of objects be the same as what I see?

The answer is: we can't know for sure.  Thus far there's no way for one person to perceive the world through another person's sensory organs and brain.  But the great likelihood is that we all see colors pretty similarly.  All of our visual receptors are put together the same way, as are the visual cortices in our brains.  To assume that even with this structural and functional similarity, each person is still perceiving colors differently, runs counter to Ockham's Razor -- so without any evidence, it seems like a pretty untenable position.

More interesting is the comparison between how we see the world and how other animals do.  Once again, we run up against the issue that we can't see through another's eyes, but at least here we're on more solid ground because we can see that different animals have differently structured eyes.  Dogs, for example, have retinas with a much higher density of rods (the structures that operate in dim light, but only see in shades of gray) and a much lower density of cones (the structures that operate in bright light, and are able to differentiate by wavelength -- i.e., see colors).  Dogs aren't completely colorblind -- their two types of cones peak in sensitivity in the blue and yellow regions of the spectrum -- but they're relatively insensitive to colors outside that.  (This explains why my dog, Guinness, routinely loses his bright orange tennis ball in the bright green lawn -- to me, it stands out from fifty meters away, but he'll walk right past it without seeing it.) 

Then, there are bees and butterflies, which have eyes sensitive not only in the ordinary visible light spectrum but in the infrared and ultraviolet regions, respectively.  There are flowers that look white to our eyes, but to a butterfly they're covered with streaks and spots -- ultraviolet-reflecting markings that advertising nectar to those who can see it. 

A flower of the plant Potentilla reptans, photographed in ultraviolet light.  To the human eye, the flower looks solid yellow -- this is what it might look like to a butterfly.  [Image licensed under the Creative Commons Wiedehopf20, Flower in UV light Potentilla reptans, CC BY-SA 4.0]

But the winner of the wildly complex vision contest is the mantis shrimp, which has sixteen different color receptors (contrasted with our paltry three), rendering them sensitive to gradations of color we aren't, as well as detecting ultraviolet and infrared light, and discerning the polarization angle of polarized light.  How the world looks to them is a matter of conjecture -- but it certainly must be a far brighter and more varied place than what we see.

The reason all this colorful stuff comes up is because of a paper that appeared last week in Proceedings of the National Academy of Sciences, called "What We Talk About When We Talk About Colors," by Colin Twomey, Gareth Roberts, David Brainard, and Joshua Plotkin of the University of Pennsylvania.  The researchers looked at how words describing different colors vary from language to language.  "The color-word problem is a classical one," Plotkin said, in an interview with Science Daily.  "How do you map the infinitude of colors to a discrete number of words?"

And, more central to this research: does everyone do it the same way?  If you showed me a series of gradations from pure blue to pure green, at what point to I switch from saying "this is blue" to saying "this is green" -- or do I call the intermediate shades by a third, discrete name?

What the researchers found was that across 130 different languages, humans tend to group and name colors the same way.  Further, if you give people tiles with varying shades of red and asked them to pick out "the reddest red," the results show remarkable consistency.

Another interesting result of the research was that the sensitivity of our eyes to color variation isn't the same from color to color; we are much better at picking out subtle variations in red, orange, and yellow than we are at seeing differences in (for example) different shades of brown.  The researchers believe this is due to a difference in what they call communicative need; since reds, oranges, and yellows are the colors of ripe fruit, we've evolved eyes that are most sensitive to variations in those colors.  "Fruits are a way for a plant to spread its seeds, hitching a ride with the animals that eat them," Twomey said.  "Fruit-producing plants likely evolved to stand out to these animals.  The relationship with the colors of ripe fruit tells us that communicative needs are likely related to the colors that stand out to us the most...  No one really cares about brownish greens, and pastels aren't super well represented in communicative needs."

So it seems like the great likelihood is that we all see the world pretty much the same way.  Well, all humans, at least.  What the world looks like to a dog, with their better dim-light vision and better motion detection, but far poorer color discrimination, can only be guessed at; and what colors a mantis shrimp sees is beyond the ability of most of us to imagine.

Study lead author Colin Twomey wonders whether the same techniques could be used to study other facets of sensory perception.  "This is something that could be carried to other systems where there is a need to divide up some cognitive space," he said, "whether it's sound, weight, temperature, or something else."

One I wonder about is the sense of taste.  We know that taste differs a great deal between different individuals, not only because everyone likes (and dislikes) particular flavors, and those preferences differ greatly; but there are some people called "supertasters" who are sensitive to minor variations in flavor that the rest of us don't even notice.  (I am most definitely not a supertaster; the joke in my family is that I have two taste buds, "thumbs up" and "thumbs down.")  The daughter of a friend of mine, for example, has amazingly sensitive taste buds, to the point that she can discern whether the coffee was brewed with filtered water or ordinary tap water.

Me, as long as it's brewed with water and not turpentine, I'm fine with it.

But that's all potential future research.  For now, we have a better idea of how each of us colors our world.  And despite our individual differences, the answer appears to be that what you're seeing and what I'm seeing look very much alike.  

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As someone who is both a scientist and a musician, I've been fascinated for many years with how our brains make sense of sounds.

Neuroscientist David Eagleman makes the point that our ears (and other sense organs) are like peripherals, with the brain as the central processing unit; all our brain has access to are the changes in voltage distribution in the neurons that plug into it, and those changes happen because of stimulating some sensory organ.  If that voltage change is blocked, or amplified, or goes to the wrong place, then that is what we experience.  In a very real way, your brain creates your world.

This week's Skeptophilia book-of-the-week looks specifically at how we generate a sonic landscape, from vibrations passing through the sound collecting devices in the ear that stimulate the hair cells in the cochlea, which then produce electrical impulses that are sent to the brain.  From that, we make sense of our acoustic world -- whether it's a symphony orchestra, a distant thunderstorm, a cat meowing, an explosion, or an airplane flying overhead.

In Of Sound Mind: How Our Brain Constructs a Meaningful Sonic World, neuroscientist Nina Kraus considers how this system works, how it produces the soundscape we live in... and what happens when it malfunctions.  This is a must-read for anyone who is a musician or who has a fascination with how our own bodies work -- or both.  Put it on your to-read list; you won't be disappointed.

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

The scent of memory

When I was about nine years old, I went to live with my paternal grandmother for a year.

Ostensibly the reason was that my parents were in the process of building a house, and where they were living -- a room in my maternal grandfather's house -- there wasn't space for a kid.  My grandmother, on the other hand, lived in a rambling old house with tons of space.  Plus, I idolized my grandma, and had a rather fractious relationship with my parents, so the move resolved several problems simultaneously.

While living with my grandma, my bedroom was in the attic.  Don't think of a cramped, dark space; it was wide open, with dormer windows and lots of separate "rooms" with various nooks and crannies and alcoves and places to explore.  Got a little hot in the summer -- this was southern Louisiana, and there were lots of fans but no air conditioning except a single window-mounted unit down in the living room -- but it was a splendid retreat for a kid who was already a bit of a loner.

Because of the heat, I often slept with the windows open, and one of the two things that will always bring back memories of that year is the sound of church bells in the distance.  My grandma's house was a couple of blocks from Sacred Heart Catholic Church, and the bells ringing in the evening reminds me of those quiet nights in the attic room.

The other, and stronger, association is the smell of old books.

My grandma loved books.  The attic walls were lined with shelves, and filled with what looked to my young eyes like thousands of books, from old cloth-bound textbooks to paperback novels, and everything in between.  The dusty, dry smell of old books brings me back instantaneously; I can almost see the book sitting in my lap as I sat cross-legged on the attic floor, feel texture of the brittle, yellowed pages and the worn cover.  The memories are vivid, detailed, and immediate.

[Image licensed under the Creative Commons Tom Murphy VII, Old book bindings, CC BY-SA 3.0]

I've always wondered why smells can evoke such powerful memories.  It's a common response, but despite this, the underlying mechanism has remained elusive.  But now a study out of Northwestern University, published this week in Progress in Neurobiology, has shed some light on the relationship between olfaction and memory -- and found that it results from an underlying structural feature of the human brain.

The team, led by neuroscientist Guangyu Zhou, studied the connections between the olfactory centers and other parts of the brain, and also looked at activity levels using fMRI technology.  They found something fascinating -- that the olfactory centers have a higher degree of connectivity with the hippocampus (one of our main memory centers) than any other sense, and the activity level in those connections oscillates to match the rate of our breathing.

"During evolution, humans experienced a profound expansion of the neocortex that re-organized access to memory networks," said study co-author Christina Zelano, in an interview with Science Daily.  "Vision, hearing and touch all re-routed in the brain as the neocortex expanded, connecting with the hippocampus through an intermediary -- association cortex -- rather than directly.  Our data suggests olfaction did not undergo this re-routing, and instead retained direct access to the hippocampus."

It does make me wonder a bit about my own case, though, because after decades of sinus problems, my sense of smell is pretty lousy.  It's not gone completely, but I certainly don't have the sensitive nose that many have.  (Which has a variety of downsides, including explaining why I was assigned to clean up when our septic tank backed up, and also give our dogs baths the time they got skunked at five AM.)  Now, there's the additional complication of COVID-19 infection wiping out people's senses of smell entirely.  "Loss of the sense of smell is underestimated in its impact," Zelano said.  "It has profound negative effects of quality of life, and many people underestimate that until they experience it.  Smell loss is highly correlated with depression and poor quality of life...  Most people who lose their smell to COVID regain it, but the time frame varies widely, and some have had what appears to be permanent loss.  Understanding smell loss, in turn, requires research into the basic neural operations of this under-studied sensory system."

I'm a little dubious that my poor sense of smell has anything to do with my tendency toward depression, but that they correlate in my case is at least interesting.  It's reassuring that I still do have memories triggered by smells, so even if I might not be having the full experience of the sense of smell, that part of the system still seems to be working just fine.

Especially the smell of old books and memories of living with my grandmother.  That one is intact and fresh, and (fortunately) a very positive association.  Add it to some sounds -- church bells, the rhythmic drone of an oscillating fan, the song of whippoorwills at night -- and I can close my eyes and for a moment, be nine years old again.

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I've always been in awe of cryptographers.  I love puzzles, but code decipherment has seemed to me to be a little like magic.  I've read about such feats as the breaking of the "Enigma" code during World War II by a team led by British computer scientist Alan Turing, and the stunning decipherment of Linear B -- a writing system for which (at first) we knew neither the sound-to-symbol correspondence nor even the language it represented -- by Alice Kober and Michael Ventris.

My reaction each time has been, "I am not nearly smart enough to figure something like this out."

Possibly because it's so unfathomable to me, I've been fascinated with tales of codebreaking ever since I can remember.  This is why I was thrilled to read Simon Singh's The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography, which describes some of the most amazing examples of people's attempts to design codes that were uncrackable -- and the ones who were able to crack them.

If you're at all interested in the science of covert communications, or just like to read about fascinating achievements by incredibly talented people, you definitely need to read The Code Book.  Even after I finished it, I still know I'm not smart enough to decipher complex codes, but it sure is fun to read about how others have accomplished it.

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

Canine illusions

I've always had a fascination for optical illusions.

The enjoyment of bizarre trompe-l'oeil is connected to a persistent theme in my fiction; how do we know what's real?  If something occurs that challenges our notions of how things are, by what criteria could we know if we're seeing reality -- or if it's a malfunction in our frequently errant sensory-perceptual systems?

My favorite optical illusions are ones where even once you know what's going on, your mind just won't accept it.  Our brains, apparently, are very prone to hanging on to a solution to a perceptual anomaly even once it's been conclusively demonstrated that they've got it wrong.  The best example of this I know of is the checker shadow illusion:

In the above image, which square is darker, A or B?

If you know anything about optical illusions, you've probably guessed that they're the same darkness, and you'd be right if you did.  But I'd bet cold hard cash that even once you know the two squares are the same darkness, you can't actually see it that way.  (In fact, if you doubt they are of equal darkness, use some scraps of paper to cover up everything but a vertical strip of the image, to eliminate the green cylinder and most of the checkerboard.  The fact that they're the same will be obvious.  Then remove the paper, and voilà -- you'll be back to seeing A as darker than B.)

Another fine example of this phenomenon is the hollow-face illusion, which seems to occur because our brains have a finely-developed ability to see nuances of other human faces, but the concept of an inside-out face is so far out of anything we typically experience that we just can't process it.  Check it out:

A lot of optical illusions have to do with the fact that we often interpret what we see based upon comparisons, and those comparisons persist even once we know they're inaccurate.  (That's the key to the checker shadow illusion; because we think square B is in shadow, it must be intrinsically lighter in color than square A.)  It's also what made the infamous blue dress/white dress illusion so maddening; apparently it works because we judge something's color not only by the intrinsic frequencies of the light striking our eye, but by comparison to the color(s) surrounding it.  So someone who focuses on one part of an image and judges the rest of the image based upon that will come to a different conclusion than someone who does the same thing but starting with a different part of the image.

A lot of size-based illusions work in a similar fashion, such as the Ebbinghaus-Titchener illusion, in which the question is to determine which of the two orange circles is larger:

You've undoubtedly already guessed that they're the same size, but it's a remarkably persistent illusion even when you know that.  The right-hand circle looks larger because we're judging its size by comparison to the small dots surrounding it; and the opposite holds for the left-hand circle.

The topic of optical illusions comes up because of a cool study out of La Trobe University (Australia), led by psychologist Sarah Byosiere.  Byosiere became interested in optical illusions a few years ago, and wondered whether humans' advanced brains made us fall for them more easily -- we're always calculating, comparing, weighing options, which brings with it some pitfalls -- and whether other animal species might not be fooled.

So she decided to test dogs.  Using copious amounts of dog cookies, she trained some dogs to interact with a touch screen, rewarding the dogs if they touched their noses to the larger of two circular shapes shown.  Once they got good at it, she threw the Ebbinghaus-Titchener illusion at them.

And they fell for it.  Apparently dogs think the right-hand circle is larger, too.

What's even more fascinating is that dogs didn't fall for the Delboeuf illusion...

 ...which you'd think would work precisely the same way.  Getting tricked by the Delboeuf illusion is apparently pretty ubiquitous in humans, which is why restaurants have discovered that a medium-sized entrée looks like a more generous serving in a small plate than in a larger one.  But dogs presented with two plates of food, which differ in the plate size but not in the quantity of food, showed no preference whatsoever for the smaller plate.

As a side note, however, I do wonder if the apparent failure of dogs to get taken in by the Delboeuf illusion isn't because of faulty experimental design.  I know my own dogs don't seem to respond to portion size in their (equal-sized) food bowls.  I can fill one to overflowing and put only a handful of kibble in the other, and my dogs will generally go for whichever bowl is closer.  "Oh, well, I can always go for the other bowl once I'm done with this one," seems to be their general attitude, along with "Any food is a good thing."

Byosiere and her colleagues have expanded their research into other illusions, and I encourage you to go to the link I posted and check out what she and others have done.  She's also started a citizen-science effort called “What the Fluff!?” to study how animals respond to an illusion you probably have seen on YouTube -- where a pet owner holds a sheet up in front of them, and drops the sheet while simultaneously ducking out of sight, and seeing how the pets respond to their owners' apparent vanishing act.  "We’re asking owners to do this at home with their dogs," Byosiere said.  "We’ll be analyzing the footage and seeing if we can make any conclusions about object permanence and violation of expectation in that kind of magic trick."

So if you're inclined, try playing some mind games with your pets, and send her your results.  I may try it with my dogs and see what happens.  My guess is Guinness might fall for it and try to figure out what happened, but our hound Lena, who shows the level of energy and intelligence usually associated with a plush toy, would probably not notice if I mysteriously vanished.  Or if she did notice, she'd kind of shrug and go, "Oh, well, I'm sure he'll be back at some point" and resume the very important nap she'd been taking before I started bothering her.

Either way, it might be interesting to see how they respond.  If you try it, let me know in the comments section what your results were.  And now, I'm off to play a round of Confuse-a-Dog.

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What are you afraid of?

It's a question that resonates with a lot of us.  I suffer from chronic anxiety, so what I am afraid of gets magnified a hundredfold in my errant brain -- such as my paralyzing fear of dentists, an unfortunate remnant of a brutal dentist in my childhood, the memories of whom can still make me feel physically ill if I dwell on them.  (Luckily, I have good teeth and rarely need serious dental care.)  We all have fears, reasonable and unreasonable, and some are bad enough to impact our lives in a major way, enough that psychologists and neuroscientists have put considerable time and effort into learning how to quell (or eradicate) the worst of them.

In her wonderful book Nerve: Adventures in the Science of Fear, journalist Eva Holland looks at the psychology of this most basic of emotions -- what we're afraid of, what is happening in our brains when we feel afraid, and the most recently-developed methods to blunt the edge of incapacitating fears.  It's a fascinating look at a part of our own psyches that many of us are reluctant to confront -- but a must-read for anyone who takes the words of the Greek philosopher Pausanias seriously: γνῶθι σεαυτόν (know yourself).

[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!]