The effect of explanation on MMN presence in Mcgurk effect

The red line indicates the averaged brain waves in the deviant condition (audio playing “BA” while mouth pronouncing “FA”). The blue line indicates the averaged brain waves in the standard conditions ( audio playing “BA” and mouth pronouncing “BA”).

        Our experiment focused on the auditory illusions known as the McGurk Effect. The McGurk effect shows that visual cues can affect what a person hears. This is shown when  mouth pronunciations in a video can affect what a person hears. Even when the audio only plays “ba, ba, ba”, if the mouth pronounces “fa”, the person will hear “fa, fa, fa”. In cognitive science we can use certain brain waves as markers for certain activities in the brain. We wanted to see if explaining the McGurk effect to participants would affect the brain wave component known as Mismatch Negativity (MMN). The MMN is found in the 100-400 millisecond range after stimuli is shown.  When it appears, this component shows that the brain registered the mouth was pronouncing a different word than the sound playing- in other words, it was not fooled by the illusion.

We averaged the brainwaves found in two specific electrodes- FZ and OZ. The FZ electrode is found in the frontal lobe of the brain, which is where we would expect the MMN to show. The OZ electrode is in the occipital (back) of the head, which is where we should not see an MMN. No MMN was found in the OZ electrode area, as expected. We found that individuals who were not informed about the illusion did not have an MMN wavelength (top left graph), while individuals that did get it explained did show the MMN (top right graph).  This is interesting because although all participants reported experiencing the illusion, those who were explained the illusion had, on an unconscious level, not been fooled by the illusion. Their brain noticed the difference.

Research Justification

Here is an excerpt from the IRB we submitted for review before beginning the experiment. The original document contains 20 pages of content. This section describes our justification for our experiment:

        The McGurk effect, discovered by Harry McGurk and John MacDonald, is an audio illusion where visual information is powerful enough to cause a change in the perception of audio information. In the original study done by McGurk, different lip movements caused the perception of auditory stimuli to change. For example, if a person watched a video of a person mouthing the syllable “va”, but they played the syllable “ba”, they would  hear “va” instead of “ba”. It was also recorded that sometimes the perceived sound was a fusion of both the auditory and the visual information given:  playing the lip movements made for the syllable “ga” while playing the sound “ba” lead to the perception of the sound “da”.  The McGurk effect is very curious because even after participants are informed about what the McGurk effect is, they still experience the same perceptual illusion.

        Originally, the McGurk effect was evaluated using behavioral questions asking participants what syllable they heard. Another way to test for the McGurk effect is to use the ERP marker known as a Mismatch Negativity, or MMN. The MMN is an ERP component associated with higher order processing in the auditory cortex. The MMN has been successfully elicited in individuals from all ages, from newborns, to infants, to adults, and even in the womb. It is a well studied indicator of the auditory detection of changes in acoustic stimuli; in other words, it shows when the brain is detecting unusual changes in reliable, unchanging patterns. This type of stimuli uses the principle of the oddball paradigm, where in a sequence of the same stimuli there is is one deviant stimulus.  For example, an MMN would be elicited to “va” in the following auditory stream: “ba, ba, ba, va, ba, ba,…” This is used to the benefit of studying the McGurk effect, since a deviant sound perceived to sound the same as the repeating syllable will not elicit the MMN even though the actual acoustic stimulus is different.

        In the study done by Saint-Amour et al. (2006), the McGurk effect was used in conjunction with the MMN in the method outlined above. Participants listened to audio stimuli while watching lip movements while hooked up to an EEG cap recording the ERP information associated with each trial. In addition to looking at the ERP information the researchers used source analysis to determine from where in the brain these ERP components were being generated in order to give insight into the specific cortical areas that were associated with the tasks. This analysis allows a look into the systems needed to simultaneously process the visual and auditory information not only to stimulate the McGurk illusion, but also similar tasks like listening to music or participating in a conversation.

        The goal of our study is to replicate the study done by Saint-Amour et al. using source analysis as well as their stimuli. We are interested in seeing if informing participants about the McGurk illusion will alter the strength of the MMN markers elicited during the experiment. We know that the effect is powerful enough to continue being perceived even after explanation, but we are curious as to how this knowledge might alter the MMN we record. Half of the participants will read an explanation on the McGurk effect (experimental group) while the other half will read a description of molecular gastronomy (control group). Both the MMN and the source analysis of each group will be compared to see if there is a significant difference between the two. We predict that individuals that read the McGurk illusion explanation will have a weaker MMN response than individuals who do not read the explanation of the illusion they are being presented with.


Kislyuk, D.S., Möttönen, R., and Sams, M. (2008). Visual processing affects the neural basis of auditory discrimination.  Journal of Cognitive Neuroscience, 20, 2175-2184

McGurk, H., and MacDonald, J.(1976).  Hearing lips and seeing voices. Nature, 264, 746-748.

Näätänen, R., and Kreegipuu, K.  (2011).  The Mismatch Negativity (MMN). In S. Luck & E. Kappenman (Eds.), The Oxford Handbook of Event-Related Potential Components.  Oxford University Press.

Rosenblum, L., Schmuckler, M.A., and Johnson, J.A. (1997). The McGurk Effect in infants. Perception and Psychophysics, 59, 347-357.

Saint-Amour, D., De Sanctis, P., Molholm, S., Ritter, W., and Foxe, J. (2006). Seeing voices: High-density electrical mapping and source-analysis of the multisensory mismatch negativity evoked during the McGurk illusion. Neuropsychologia, 45, 587-597.

Skipper, J.I., van Wassenhove, V., Nusbaum, H.C., and Small, S.L. (2007). Hearing lips and seeing voices: How cortical areas supporting speech production mediate audiovisual speech perception. Cerebral Cortex, 17, 2387-2399.

Yu, X., Lui, T., and Gao, D. (2015). The mismatch negativity: An indicator of perception of regularities in music. Behavioral Neurology, 2015, 1-12.



The truth is, you can’t trust what you see. Your body is fallible. Your mind is fallible. You are fallible. You never know if what you’re seeing and hearing is true. That’s obvious and simple if you consider it for even a moment, a cliché practically. But think it through. Think through what it means.

That ringing in your ears? Do you know what it is? Of course not – how could you. Standing where you are right now, surrounded by colors, lights, sounds, and the chaos of this room, how could you possibly pin down anything? It’s a disaster zone for your brain, an utter deluge of information, an overload so complete that you don’t even realize it.

Pause for a moment, please. Stand still and slow your breathing. Open your eyes and your ears. Take it all in. Really. Don’t give me any bullshit – actually try to absorb it all. Every single light and their varying shades; the shadows spawned by the folds of the fabrics; the reams upon reams of said fabrics, burying this space in their stitching; the graphs and charts and data points staring at you from that wall and that pillar; the music – no, no that track, but that other one instead; the voices whispering in your ears and the illusions taking place all around you at this very moment.

You cannot process all of that at once. There’s too much. At a certain point, your brain just stops letting you know that some of these things are even happening. You filter it out. Your brain lies to you.

You are drowning in a sea of deception and you can’t even tell.


By Conor Flanagan


She’s a perfectly ordinary girl, however you define that.

How can she fit everyone’s individual definition of ordinary, you ask? First off, you should perhaps confront the obvious strangeness and pointlessness of you, a disembodied placeholder entity asking me, a disembodied narrator, such a cliché question. Second off, you should consider why anyone would bother to ask this unnecessary and odd question in the first place.

With those questions in mind, we shall now move on to more relevant concerns. Please try to stay focused.

She’s a perfectly ordinary girl, however you define that. She is preparing to enter a very strange place. It’s completely safe, of course, just quite strange. It is an exploration of the senses – not her senses in the specific, but the senses, in the abstract. They’re very different things and exhibits on these two separate topics would be quite different experiences.

She, of course, does not know what to expect on her journey. She merely saw a sign that piqued her curiosity, a sign featuring the image of laughter. Not the image of a person laughing, mind you – the image of the sound waves produced by laughter. This image intrigued her, and so she followed its instructions and made her way over to this exhibit.

She walks down the stairs carefully, her flats creating a clacking sound that most would be more inclined to associate with heels. Setting this odd contradiction aside, for presumably she no longer noticed this mismatch, she proceeds down into the darkness.

Dimness is a slightly more applicable term in this context. It is very dark at the bottom of the stairs, but hints of light bled through from just around the corner. Being a human, it is in her nature to follow this light, and she thus promptly acted on her instinct and skittishly fled from the darkness.

I shall pause now and forewarn you, dear fellow disembodied presence, that we are, to say the least, entering an odd environment. In may indeed be so odd that words will not suffice to describe it. I shall thus only give the description a token effort, including enough information to orient you but not so much as to bury you. I do believe that you will appreciate this, especially as the space and effort I save in making that decision will allow us to spend more time on our primary subject.

Said subject is now following the path and wandering cautiously into the exhibit. The exhibit is a veritable cornucopia of stimuli, with fabric draped across the walls, strings zig-zagged across the room at eye level, a massive silken archway slung across the center of the space, and the eerie white glow of a projector against a distant wall. The visuals are accompanied by a soft music lazily drifting through the air, intercut with snatches of audio from what seems to be a person speaking. Tucked into a shadowy corner sits a small man, staring straight at the entrance and blinking slowly, typing methodically away on a remarkably loud keyboard.

Her reaction, unsurprisingly, is one of confusion and curiosity. The display is not so impressive as to elicit a truly awed response from her, but it certainly captures her interest from the very beginning. She looks around the room slowly and carefully, eyes sparkling, reflecting shreds of light from the weak sources in the exhibit.

Courteous and dedicated student of art that she is, she stands still, running through this examination process while rooted to the spot for several minutes. When she finally begins to move again, she does so quietly and carefully, showing appropriate deference to the piece.

The solitary nature of her visit likely contributes to her cautious movement as well; other than the small man sitting eerily in the corner, she is alone here. And with the almost-taboo aura emanating from that man, it appears that communicating with him in any way will be unlikely for her. Thus, she undertakes this journey alone.

To answer your obvious and immediate question – yes, of course we are here with her as well. But as this story should have made clear by now, the girl is not particularly aware of our presence. We are merely “along for the ride,” so to speak, floating along behind her and observing for our own purposes. Well, my own purposes, at any rate. I don’t know what you’re seeking here.

Regardless of your goals, however, you should make a better effort to respect this process and focus your attention on the subject’s reactions to the exhibit. At a bare minimum, if you insist on asking questions, please ask better ones than those you have thus far offered.

Now, in my efforts to address your curiosity, the subject has moved deeper into the room. She has taken a lengthy piece of string proffered by a nearby bowl and is weaving it through scattered hooks as she moves through the space, adding a small component of her own to the larger exhibit. In the process, she is pausing every so often to examine particular bits in greater depth. She lingers over a piece of fabric, hesitating for a moment before reaching out to run her hand along it. She absentmindedly loops her string multiple times around a single hook as she squints through the archway, trying to see past the shadows cast by the stark light of the projector.

Unsurprisingly, she waits only another moment before creeping forward through the archway, pausing only to slip the string across another hook. The man in the corner continues to clack away at his keyboard, but after a few nervous glances from the subject earlier (glances that we missed), she has resolved to ignore his presence. Further, the cloth archway muffles his clacking once she passes through it, rendering the question moot in the first place.

There is more to see beyond the archway – a recordplayer lurking in the lower folds of the curtains, mannequin heads dyed a half dozen colors mounted on the left wall – but she barely seems to notice these things.

No, the real attraction of this space is the buzzing projector that drew her attention in the first place. The bright white light glares harshly against the wall, cut through only by the small black text zipping across the display at lightning pace.

She steps forward, just as curious as you, trying to get a better look at what the text says, squinting now not for sight but because of the pain caused by the burning light. She pauses for a moment to take in the words and is greeted only by her own actions.

It would be more appropriate to call it an accounting of her actions in the exhibit thus far, an accounting that is being updated in real time. Every motion the subject has made since turning the corner into the space has been recorded, and even the slightest twitches are now being blasted onto the wall for anyone to read.

In some ways, that sounds less frightening than it actually was. And perhaps for you, such a thing was always going to be less frightening – you are not the subject of this text, after all. But she is. And as I mentioned earlier, she has no idea that she is not alone in here. As far as she knows, she is completely isolated. Utterly alone except for the man in the corner, clacking away, noting her movements and projecting each one onto this screen in some sort of warped show for her eyes only.

It is, to say the least, a disturbing, creepy trick. Shrouding the reveal of this element behind the silk archway just amps up the level of creepiness, creating a moment in which the subject’s stomach sinks as her brain puts the pieces together. The space twists on that moment, the added layer seemingly darkening the whole room. Her isolation in this room only enhances the effect, forming a brief window in which it seems that she is trapped in here with the observer.

For a moment, that window persists and we are able to observe a range of emotions struggle across her face as she processes the nature of the experiment.

But it is shattered by the sound of footsteps padding slowly down the stairs. Given our position closer to the door, we of course notice it before she does, but she’s not too far behind. She jerks in surprise and twists around, instinctively withdrawing deeper into the shade of the archway even as she cranes to see the source of the footsteps.

I see that you want this to further amp the pressure in the room, a new element brought into the exhibit at this exact moment to make the environment even stranger and creepier. The acoustics of the room promote your goals too – the footsteps seem heavy and dragging as the sound echoes through the room, distorting itself as it bounces across surfaces. It gives off the impression that something threatening is approaching.

Tragically for you, but fortunately for the rest of us, no such thing is occurring; the room is merely designed to take advantage of opportunities such as that. Had we been downstairs before our subject came down, you would have heard how the acoustics warped the clacking of her shoes, creating a sharper sound that would have caused many to jump.

In truth, it’s just another group entering the exhibit. It is a public installation, after all. No need for any of the subjects to be isolated and alone in there. Why, it would be the height of foolishness to enter such an eerie space all by oneself. In a space designed to make people uneasy, there’s no need to make that task simpler.

Getting back to the subject…

Once she sees the other group turn the corner and look around in wonder themselves, our first subject visibly relaxes. It seems that the brief spell she was under has broken. She looks around sheepishly at her crouched, hidden position, and gingerly extricates herself, turning her back on the projection on the wall and stepped out from under the archway. Once freed from the archway, the tension continues to spill out of her. The sight of the observer continuing to clack away, his attention now clearly flickering between her and the new group, gives her pause, but she shakes it off quickly. It’s just an installation.

The other group glances at her curiously as she strides out of the room, but she doesn’t bother to acknowledge them. She has clearly had her fill and is ready to leave.

Drinking Sounds

She tilts her head down and cracks an eyebrow, giving you all a wide-eyed, expectant look. “But you all didn’t come just for that stuff, right?” she says, dragging out the last word.

She turns away from you and throws her arms to her sides, tilting her head back up and exclaiming, “You came for the sound bar!”

A curtain opens as she raises her hands, revealing a small dark space, lit by clusters of sparkling lights weaved around the installations where light bulbs once sat. The dim lighting drew all focus to seven shot glasses arrayed across a bar, each with its own share of sparkling lights circled around it. Behind them, in the shadows, sat the mountains of bottles just waiting to be sampled.

She looks back at all of you, one eyebrow still raised, and bobs her head. “Yeah,” she says. “Pretty impressive, huh? We’ve got about a hundred different sounds here for you to sample.” She gives everyone a conspiratorial look and leans in as she says, “Best sound bar in the state, you know?”

You might not have known exactly what you were getting into by walking into this club, and this tour guide has been about equal parts helpful and enigmatic. But this you knew was here. The sound bar was the big draw after all, at least for you. There was something for everyone (well, maybe not quite) in here, but this was the thing for you.

There’s a moment of quiet as you and the other members of your group gawk silently at the display, no one willing to speak and pierce the eerie murmurings drifting down from the ceiling.

She isn’t standing for any of that though. She holds the conspiracy face for a moment, twisting her head back and forth between each of you, twitching her eyebrows occasionally for emphasis. But once the silent hesitation stretches out long enough (too long really), she pulls her head back and flashes a sterner, more expectant look. “Well, come on now!” she cries, gesturing forcefully toward the shot glasses. “Someone step up!” she orders.

Compelled by the force of her voice, you step forward, bringing yourself up to the center shot glass. She smiles and nods. “Good, good,” she says, “That’s just what we like to see. What do you want to sample today?”

She leans forward over the bar and starts plucking out bottles. “We’ve got thunderstorm, we’ve got ocean, we’ve got forest, and jungle cats, and city and static and speech – make a call, we’ll give you just what you need.”

“Uh… how about city?” you suggest half-heartedly, simply landing on the first bottle label you see. You’ve never done this before, so you don’t really know your tastes yet.

She nods, her face lapsing into neutrality. “A wise decision,” she says sagely, in that way where you’re pretty sure she’s sincere, but she could be messing with you. She pulls out the city bottle again and tips it over your shot glass. A clear liquid spills and cascades into the glass, collecting more like thin syrup than a glass of water.

She pops the bottle back down and turns to you, raising both her eyebrows and offering her increasingly familiar expectant face. “Drink up!” she encourages.

You look down at the shot glass and shrug. Here goes nothing. You reach down, grab the glass, and down it just like any other shot.

You taste nothing as the liquid passes your lips, not even the taste of water. But the soundscape erupts, a city springing to life in your brain. The sounds start slow and weak at the first drops, but explode in power as the full shot washes down. Honking horns and shouting pedestrians, street vendors and protest groups, a thousand little conversations and a dozen huge ones – all of these envelop your mind in an instant at staggering volume.

You jerk back and gasp at the force of it, wincing in pain. But it passes as quickly as it came, the liquid sliding unnoticeably down your throat and the sounds instantly dropping off. The volume is like a crack of thunder, massive and dramatic for a split second before fading softly into the distance, leaving only dim rumblings in its wake.

You shake your head in astonishment and eye the shot glass as she sits next to you, waiting, still silent.

Curious, you lift the shot glass to your eye and examine it, noting the few remaining droplets. You tilt your head back and the glass up, coaxing a few stubborn drops onto your tongue.

Each individual drop offers the briefest flash of another city sound. Just a horn, not any shouts.  Three drops drip onto your tongue, and each brings the volume up a dial higher before sinking back down to normal, leaving behind an echoing memory.

“The shots give you that big burst of stimuli,” your tour guide says, eyeing you as she casually reaches out and tips another shot into your glass. “Try a slow sip. It’s more immersive.”

You nod breathlessly and take hold of the glass once more. You tip the liquid into your mouth, carefully this time. Again the sounds envelop your brain, surrounding you in the experience. But it’s less powerful this time, less destructive.

The screeches of car horns are distant flavor, undercurrents and background noise, not claxons in front of your face. The sounds of pedestrians walking and talking form the baseline of the taste, the thick, main current, as though you have a particularly good pair of headphones. Individual words and phrases slip through like dashes of spice, but they’re merely subtle hints, not forceful screams.

Without the intense pressure of the shot, you can focus too on other, slighter noises: echoes of the wind rippling between the skyscrapers; distant sounds of building construction and roadwork; the low buzz of neon street signs at night.

The drink disappears all too quickly, the experience rising up around your mind and receding back into the distance, leaving only slivers of sound behind as aftertaste. You open your mouth and breathe deeply, the air leaving tingles behind, as though you had just finished a mint.

“Come one, come all!” announces your guide, catching you off guard as she steps to the side and gestures to the array of sounds stacked at the bar. “There’s plenty for everyone!”

Sinking down from your high, you notice that the rest of the group is beginning to move forward now, emboldened by your successful experiment.

They all step forward and reach out for various drinks: Ocean Spray, Under-the-Sea, Soaring Sky, Warzone, Calvary Charge, Conversationalist – the list goes on and on. A cornucopia of sounds just awaiting your taste buds.

You eye them all carefully yourself and then reach out and resume your drinking.

Sensory Deprivation: Horror

It’s not there. My arm isn’t there.

I can feel it, yeah. The muscles are moving just fine. I feel pricks of cool air pierce the sheen of water on my skin. I even feel drops of water fall down from my arm and splash against my chest. I have nearly every sign I could imagine to confirm that my arm is right there working just as well as it always does.

But I can’t see it. It’s pitch black and I can’t see a thing, not even a shadow of a shadow, not even the angle between two walls, not even my own goddamned arm.

Okay, just keep calm, I’ve gotta just keep calm. Don’t let the breathing get out of control, don’t start the hyperventilation, just breathe in and out. There we go, there we go, a nice rhythm. That’s what we need. That’s what we need.

It’s not enough though is it, no no no, it’s not enough to just control my breathing and still my body. I don’t know what’s happening. I still don’t know if my arm is there. I feel a choking, roiling cloud climbing up my body, seeping into my pores and clawing at my mouth to really strangle me properly, so I try to push it back. I try to take stock.

Think. Think it through. Break out of the haze, you can do something about this.

Okay, I can reach over and grab one arm with the other. Good. That’s solid, I can feel that. I still can’t see it, but I can feel it so I know it has to be there. Or, at least, I can tell myself I know that long enough to come down from the panic.

What about the rest of my body?

Yeah, okay, I can pat that down too.

My fingers dance shakily down my body, hitting everything they can. I pull my legs in tight so I can grasp as my feet. I raise my hands back behind my head and run my fingers through my hair. Everything is still there. I can’t see it, but it’s all still there.

My breathing is still labored, the hyperventilation just off the horizon, but that’s a layer of security down. That’s a step toward calm.

But there’s too much left to panic about. I can’t see anything. I don’t know where I am. I don’t even know if I’m alone. I make myself think back to stepping into the pod, seeing the lights and the contours of the tub, the height of the ceiling and the emptiness of the chamber. I was all alone then, I must be all alone now.

I can’t hear either though.

I can’t see and I can’t hear. The room directly outside the chamber is just as dark as the chamber itself. Someone could have slipped in from there without my even knowing. There’s no way to tell. 8 feet of darkness between the ceiling and me. 8 feet of nothing where anything could be hiding. I need to check. I need to look through every nook and cranny and make sure that I’m safe and alone here. That’s the only way I’m going to calm myself down.

But the ground is slippery. The walls are slippery. Everything is slippery and covered in water. And I’m still shaking. I can’t see my hand, but I can feel it shuddering like I just sprinted a mile. My legs won’t be much better if I stand up. I have to look though, I have to make sure that I’m safe and alone.

I jerk wildly all of a sudden, snapping out a wave of water to ricochet through the enclosed tub. I look around in a panic, searching for the sound of the voice that just whispered in my ear, look around wide-eyed for a minute before I remember that it’s impossible to see in this room.

My breath control begins to slip and I grit my teeth, trying to force my body back under my control. I heard that voice, yes, that familiar voice reproduced so terrifyingly here. Launching into another round of panic won’t do anything to help.

The panic gorges on itself though, feeding into a loop. I hear the voice again, flinch wildly and instinctively look. Before I can regain control of myself, a different voice is speaking in my other ear and I’m spinning in that direction, clumsily pulling myself into a sitting position in the shallow water.

My sight is going haywire now too and I see dark shapes spinning in pinwheels in front of me. There’s not a hint of light, but I see Ferris Wheels just above my head. I press my eyes as tightly closed as I can, so hard that my eyeballs begin to ache under the pressure.

It doesn’t help.

I see things crawling on the invisible ceiling, things clinging to the nonexistent walls. I hear drops of water and the sounds of bodies being dragged along the smooth surfaces of my prison. I hear whispered chatter spread through the room, expanding, growing, filling the room and drowning out everything else, the creatures on the walls moving in sync with the echo chamber.

I groan and flinch, my arm jerking against the wall to my right. The impact jolts me out my downward spiral, cutting off the cycle. The water ripples around me and I reach out hungrily, grasping for a way to ground myself. The feeling of the ripples on my skin calms me and the indistinct shapes and shuffling sounds fade away in my mind, heavy darkness sinking back over me.

The spell broken, I gasp and pant wildly, gulping down as much air as I can. My sense of normalcy gets some grip on my mind and I begin to relax slightly, my fists unclenching and my breathing ticking down in urgency.

But it’s still there.

I see it. In the corner up there. A shape, lurking between the walls and the ceiling, pressing itself against the sides of my little prison. I stare at the shape desperately, my breathing slowing until I’m nearly holding my breath, little inhalations and exhalations slipping in and out as quietly as I can let them. No matter how much I stare, I can’t identify what it is. It’s just sitting there. Watching me.


Sensory Deprivation

It’s silent. Actually silent. Not the kind of silent that you get at night, where the house may creak or the wind may blow. Not even the kind of silent that’s broken only by your own movements. I can feel myself move, but I can’t hear it. Sound is just an enormous void; there’s nothing there.

It’s weird, yeah, but it’s also kind of cool. Where else can you feel that sort of isolation? You’re always hearing something, even if it’s just background noise, but in here? It really is empty.

On top of that, it’s perfectly dark. Just like with the silence, the darkness is complete. There’s not even the slightest hint of light. I can’t make out so much as an outline. I lift my hand into the air over my eyes and see nothing. I only know it’s there because I can feel the movement of my arm and the impact as drops of water fall from it onto my face. I cannot see any difference between opening and closing my eyes.

I can feel the water moving around me and if I push enough, I can bump into one of the walls of the tub, so the world isn’t completely blank for me. I can reenter it to some degree. But if I lie still, the tactile stuff starts to fade. I can’t tell what’s in the water and what’s in the air. I can’t feel any part of my body unless I’m actively moving it. Even breathing starts to fade into the background.

It’s an incredibly cool feeling, to be so completely alone. It’s an isolation of your choosing, like going camping so you can see the stars instead of the smog. But with sensory deprivation, you’re not just trading in one sight for another – you’re trading in light for darkness. It’s an escape from the entire world, not just the bits that bug you.

But here’s the secret – you can choose to perceive a new world inside the tank. I can decide if I want to experience something new, something of my own creation. If I let it, my brain can fill in the gaps. It’s difficult, yes. I have to be able to shut off everything in my mind and just let my brain do it’s own thing. Nature abhors a vacuum and all that.

It’s like a waking dream.

It starts out small, just snippets of voices cracking across your eardrums. You’ve got to train yourself not to resist them, to let the sounds in even as your instinct is to freak out and try to find out where they’re from. You’re not gonna succeed; you are gonna panic.

They’ll expand from there, once you get comfortable with the input from nowhere. Full sentences and even meaningful ideas will start to pepper your mind. There are voices you recognize, of course, friends and family and the like. I’m never alone in there if I don’t want to be. After a little while, I’ll enter a sort of trance – all I have to do then is let my mind drift to someone I want to think about and I’ll hear them speaking to me.

The eyes come next and they start out simple too, with flashes of light and color like cliché screensavers. But if I keep myself relaxed, just breathing in and out, letting the sight flow, it starts to organize itself better. The light forms shapes. It goes from a pulsing blob of bright yellow to split squares and circles, with spots of orange, green, and purple scattered all around. It becomes dynamic and dramatic, overwhelming my mind, burying me in a sea of chaotic beauty, as all the while, my friends chatter cheerfully in my ears.

If you give it long enough, you hit a new stage too – the merging. The wall between sight and sound falls. I stop hearing voices and start hearing other things, things I can’t even put into words. Sounds that spark explosions of color at the edges of my mind, sounds that open up gaping whirlpools in my imagination, storms of sound that rage like hurricanes, all smashing against one another and filling my mind with a tapestry of senses that pass beyond what I can even classify as a sense.

The world changes for me. It becomes something unutterably unique.

The wave I ride in that tank is breathtaking. It is an unparalleled trip, an unmatchable high. And all of it is right there, right now, hiding behind some jagged boulder in the trenches of my mind. All I have to do is flatten the landscape and clear the interference. Create an open, hospitable world. A canvas.

My brain will take me where I need to go.

What is a scale illusion?

A binaural scale illusion occurs when two different sequences of notes are played in each ear, and when they are heard together the listener hears an unbroken scale.

Here is a recording of the illusion, with each individual sequence of notes played separately, then combined. This is best experienced through stereo headphones. (from Diana Deutch)

What is the Shepard’s Tone?

The Shepard’s Tone is an audio illusion in which we seem to hear a constantly rising tone. Much like how the lines on a barbershop pole seem to constantly rise or fall, the tones in the Shepard’s tone seem to rise forever. In reality, there are new tones introduced in the lower regions as the tones in the higher regions extend out of audible range. The average pitch stays the same, but we perceive the scale to be constantly rising into infinity.

Example of a shepard’s tone:

Here is the spectrogram of that audio recording (both are from University of Wisconsin Eau Claire)