Face forward

Life with prosopagnosia is peculiar sometimes.

Better known as "face blindness," it's a partial or complete inability to recognize people's faces.  I'm not sure where I fall on the spectrum -- I'm certainly nowhere as bad as neuroscientist and author Oliver Sacks, who didn't recognize his own face in the mirror.  Me, I'm hampered by it, but have learned to compensate by being very sensitive to people's voices and how they move.  (I've noticed that I'm often more certain who someone is if I see them walking away than I am if they're standing right in front of me.)

Still, it results in some odd situations sometimes.  I volunteer once a week as a book sorter at our local Friends of the Library book sale, and there's this one guy named Rich who is absolutely a fixture -- he always seems to be there.  I've seen him and spoken with him at least a hundred times.  Well, a couple of weeks ago, I was working, and there was this guy who was behind the counter, messing with stuff.  I was about to ask who he was and what he was doing, when he said something, and I realized it was Rich -- who had shaved off his facial hair.

Until he opened his mouth, I honestly had no idea I'd ever seen him in my life.

Then, a couple of nights ago, my wife and I were watching the Doctor Who Christmas episode "Joy to the World," and afterward got to see a thirty-second teaser trailer for season two, which is being released next spring.  Well, in season one, there was this mysterious recurring character named Mrs. Flood (played by British actress Anita Dobson) whose role we have yet to figure out, and who has the Who fandom in quite the tizzy.  And in the trailer, there's a quick clip of an old woman in formal attire watching a theater performance through opera glasses, and until another fan said, "What did you think about the appearance of Mrs. Flood in the trailer?" I had no clue -- not the least suspicion -- that it was her.

So it's kind of inconvenient, sometimes.  When people post still shots from movies or television shows on social media, I usually not only don't know who the actors are, I have no idea what film it's from (unless there's an obvious clue from the setting).  And as I've related before, there are times when even my voice-recognition strategy hasn't worked, and I've had entire conversations with people and then left still not knowing who it was I'd been talking to.

The reason the topic comes up (again) is some research out of Toyohashi University of Technology that was the subject of a paper in the Journal of Vision last week.  The researchers were trying to figure out if humans have a better innate ability to filter out extraneous visual distractions when it comes to facial recognition than they do for recognizing other objects.  Using a technique called "continuous flash suppression" (CFS), they presented volunteers with fast-moving high-contrast images in one eye, and a target image in the other, then using an fMRI measured how long it took the brain's visual recognition centers to "break through" the distraction and recognize the target image.

If the target image was a face -- or "face-like" -- that breakthrough happened much faster than it did with any other sort of image.  And, interestingly, the breakthrough time was significantly slowed for faces that were upside-down.

We're wired, apparently, to recognize right-side-up human faces faster than just about anything else.

"Our study shows that even vague, face-like images can trigger subconscious processing in the brain, demonstrating how deeply rooted facial recognition is in our visual system," said Makoto Michael Martinsen, who co-authored the study.  "This ability likely evolved to help us prioritize faces, which are critical for social interaction, even when visual information is scarce...  [However] we didn’t consider factors like emotion or attractiveness, which can affect facial perception...  Despite this, our study highlights the brain’s incredible ability to extract important information from minimal cues, especially when it comes to faces.  It emphasizes the importance of facial features in both conscious and subconscious perception and raises interesting questions about how this mechanism evolved."

Naturally, I found myself wondering how face-blind people like myself would do in this task.  After all, it's not that we can't tell something is a face; it's that the visual information in a face doesn't trigger the same instantaneous recall it does in other people.  When I do recognize someone visually, it's more that I remember a list of their features -- he's the guy with square plastic frame glasses and curly gray hair, she's the woman with a round face and dark brown eyes who favors brightly-colored jewelry.  This, of course, only takes me so far.  When someone changes their appearance -- like Rich shaving off his beard and mustache -- it confounds me completely.

So I'm curious whether I'd be like the rest of the test subjects and have faster recognition times for faces than for non-face objects, or if perhaps my peculiar wiring means my brain weights all visual stimuli equally.  I'd be happy to volunteer to go to Japan to participate, if anyone wants to find out the answer badly enough to spot me for a plane ticket.

No?  Oh, well, perhaps that'll be the next phase of Martinsen et al.'s research.  I'm willing to wait.

Until then -- if I know you, and happen to run into you in the local café, keep in mind I may have no idea who you are.  It helps if you start the conversation with, "I'm _____" -- I'm not embarrassed by my odd neurological condition, and it's better than spending the day wondering who the person was who came up and gave me a hug and asked about my wife and kids and dogs and whatnot.

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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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