Watch your tone!

You probably know that there are many languages -- the most commonly-cited are Mandarin and Thai -- that are tonal.  The pitch, and pitch change across a syllable, alter its meaning.  For example, in Mandarin, the syllable "ma" spoken with a high steady tone means "mother;" with a falling then rising tone, it means "horse."

If your mother is anything like mine was, confusing these is not a mistake you'd make twice.

A pitch vs. time graph of the five tones in Thai [Image licensed under the Creative Commons Thtonesen.jpg: Lemmy Laffer derivative from Bjankuloski06en, Thai tones, CC BY-SA 3.0]

English is not tonal, but there's no doubt that pitch and stress change can communicate meaning.  The difference is that pitch alterations in English don't change the denotative (explicit) meaning, but can drastically change the connotative (implied) meaning.  Consider the following sentence:

He told you he gave the package to her?

Spoken with a neutral tone, it's simply an inquiry about a person's words and actions.  Now, one at a time, change which word is stressed:

• He told you he gave the package to her?  (Implies the speaker was expecting someone else to do it.)
• He told you he gave the package to her? (Implies surprise that you were told about the action.)
• He told you he gave the package to her? (Implies surprise that you were the one told about it)
• He told you he gave the package to her? (Implies the speaker expected the package should have been paid for)
• He told you he gave the package to her? (Implies that some different item was expected to be given)
• He told you he gave the package to her? (Implies surprise at the recipient of the package)

Differences in word choice can also create sentences with identical denotative meanings and drastically different connotative meanings.  Consider "Have a nice day" vs. "I hope you manage to enjoy your next twenty-four hours," and "Forgive me, Father, for I have sinned" vs. "I'm sorry, Daddy, I've been bad."

You get the idea.

All of this is why mastery of a language you weren't born to is a long, fraught affair.

The topic comes up because of some new research out of Northwestern University that identified the part of the brain responsible for recognizing and abstracting meaning from pitch and inflection -- what linguists call the prosody of a language.  A paper this week in Nature Communications showed that Heschl's gyrus, a small structure in the superior temporal lobe, actively analyzes spoken language for subtleties of rhythm and tone and converts those perceived differences into meaning.

"Our study challenges the long-standing assumptions how and where the brain picks up on the natural melody in speech -- those subtle pitch changes that help convey meaning and intent," said G. Nike Gnanataja, who was co-first author of the study.  "Even though these pitch patterns vary each time we speak, our brains create stable representations to understand them."

"The results redefine our understanding of the architecture of speech perception," added Bharath Chandrasekaran, the other co-first author.  "We've spent a few decades researching the nuances of how speech is abstracted in the brain, but this is the first study to investigate how subtle variations in pitch that also communicate meaning are processed in the brain."

It's fascinating that we have a brain area dedicated to discerning alterations in the speech we hear, and curious that similar research on other primates shows that while they have a Heschl's gyrus, it doesn't respond to changes in prosody.  (What exact role it does have in other primates is still a subject of study.)  This makes me wonder if it's yet another example of preaptation -- where a structure, enzyme system, or gene evolves in one context, then gets co-opted for something else.  If so, our ancestors' capacity for using their Heschl's gyri to pick up on subtleties of speech drastically enriched their abilities to encode meaning in language.

But I should wrap this up, because I need to go do my Japanese language lessons for the day.  Japanese isn't tonal, but word choice strongly depends on the relative status of the speaker and the listener, so which words you use is critical if you don't want to be looked upon as either boorish on the one hand, or putting on airs on the other.

I wonder how the brain figures all that out?

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The gift of a voice

I can think of no more terrifying disorder than locked-in syndrome.

Locked-in syndrome, also called a pseudocoma or cerebromedullospinal disconnection, is a (fortunately) rare condition where the entire voluntary muscle system shuts down but leaves the cognitive facilities relatively intact.  The result: you can't move, speak, or respond, but your brain is otherwise functioning normally.

You are a prisoner inside your own useless body.

The most famous case of locked-in syndrome was French journalist Jean-Dominique Bauby, who suffered a massive stroke at age 43 and lost control of his entire muscular system except for partial control over his left eye.  This at least allowed him to eventually communicate to his doctors that he was still conscious, and -- astonishingly -- he used that tiny bit of voluntary muscular movement to direct a cursor on a computer screen and painstakingly, letter by letter, write a book about his experience.  It's called The Diving Bell and the Butterfly, and it is simultaneously devastating and uplifting -- a paean to the human spirit's ability to rise above a level of adversity that, thankfully, very few of us will ever face.

Thanks to an article last week in IEEE Spectrum, I just found out about a new prosthetic device that will give people who have lost their ability to communicate their voices back -- by converting their brain waves into words.

A team at the University of California - San Francisco has done (successful) clinical trials of a device that is implanted through a small port in the patient's skull, and is able to detect the neural signals the cerebellum and motor cortex send to the patient's larynx and mouth when they think about speaking.  From the encoded electric impulses representing the movements the person would have made, had they been able to speak, the prosthesis is able to produce whole sentences of text -- at eighteen words a minute.

Pretty impressive, especially considering that this was just proof-of-concept, so as the technology is refined, it'll only get better.  And considering that Bauby was communicating at two to three letters per minute, this is an incredible leap forward.

"We’re now pushing to expand to a broader vocabulary," said Edward Chang, who led the team that developed the prosthesis.  "To make that work, we need to continue to improve the current algorithms and interfaces, but I am confident those improvements will happen in the coming months and years.  Now that the proof of principle has been established, the goal is optimization.  We can focus on making our system faster, more accurate, and—most important— safer and more reliable.  Things should move quickly now."

They are also working toward developing a wireless version that would be able to pick up the relevant brain waves from outside, thus obviating the need to place a port in the patient's skull.  With further refinements, it might become possible to create a device that could be used on any individual who is unable to speak -- the present ones require a training period during which they learn the patient's specific neural firing patterns.  Once those are generalized, it might be possible to create a "universal translator," something Chang calls "plug-and-play."

Even what they have now is amazing, however.  Imagine regaining your voice after months or years of muteness.  I never fail to be astonished at the progress we're making in science; it seems like everywhere you turn, there are new discoveries, new inventions, new insights.

In a time when so much seems hopeless, it's wonderful that we have such stories to remind us that there are people who are working to ease the burdens of others -- and that, in the words of Max Ehrmann's beautiful poem "Desiderata," "With all its sham, drudgery, and broken dreams, it is still a beautiful world."

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Chewing gum and talking about talking

Earlier this week I looked at three cool archaeological discoveries -- cave art in Indonesia, and two finds in Egypt, one of a bone from someone killed in the battle recorded on the Rosetta stone, and the other about a researcher who found that the practice of tattooing has been around for a very long time.

But we're not done with mind-blowing archaeological stories, apparently, because there are two more that I just found out about, and which (if anything) are even cooler than the ones I wrote about Monday.

I learned of the first one from my friend, novelist and blogger Andrew Butters, whose blog Potato Chip Math is a must-read.  In this one, we find out that a team of geneticists have sequenced the DNA of a girl who lived in Denmark 5,700 years ago...

... from a wad of chewing gum.

Well, technically, it was birch sap, but same idea.  They were able to extract her DNA from the gum and sequence her entire genome, which allowed them not only to figure out what ethnic group she was from, but to make a good shot at her appearance.  She had dark skin and hair, they found, and blue eyes.  Here's an artist's reconstruction of what she might have looked like:

[Reconstruction by Tom Björklund]

The authors write:

Analysis of the human reads revealed that the individual whose genome we recovered was female and that she likely had dark skin, dark brown hair and blue eyes.  This combination of physical traits has been previously noted in other European hunter-gatherers, suggesting that this phenotype was widespread in Mesolithic Europe and that the adaptive spread of light skin pigmentation in European populations only occurred later in prehistory.  We also find that she had the alleles associated with lactase non-persistence, which fits with the notion that lactase persistence in adults only evolved fairly recently in Europe, after the introduction of dairy farming with the Neolithic revolution.

The period she lived in was when northern Europe was taken over by people known as the "Funnel Beaker Culture," so named because of their characteristic narrow-based, highly-ornamented pottery:

The 5,200 year old Skarpsalling vessel [Image is licensed under the Creative Commons Nationalmuseet, Skarpsallingkarret DO-9665 original, CC BY-SA 3.0]

"It is amazing to have gotten a complete ancient human genome from anything other than bone,'' said study lead author, evolutionary geneticist Hannes Schroeder, of the University of Copenhagen, in an interview with Science Alert.  "The DNA is so exceptionally well preserved that we were able to recover a complete ancient human genome from the sample… which is particularly significant since, so far, no human remains have been recovered from the site."

The second story goes back a great deal further in time than the little Neolithic Danish girl, though.  In fact, it kind of crosses the line from archaeology into paleontology, because in a paper in Science Advances we find out that the ability to speak might have been around in primates for twenty million years.

The study, led by Louis-Jean Boë of the University of Grenoble, analyzes the mechanics of human speech, in particular how the morphology of the mouth, trachea, and larynx allow for the production of meaningful sound.  It's been thought for years that the advent of speech occurred when our ancestors' larynxes (voice boxes) gradually moved downward, pulling the back of the tongue backward and downward as well and giving the tongue more mobility to shape sounds.  But what Boë's team found was that even if you accept that as the hallmark of speech, it goes a long way further back than we'd realized.

"First, even among primates, laryngeal descent is not uniquely human," Boë and his team write.  "Second, laryngeal descent is not required to produce contrasting patterns in vocalizations.  Third, living non-human primates produce vocalizations with contrasting patterns.  Thus, evidence now overwhelmingly refutes the long-standing laryngeal descent theory, which pushes back 'the dawn of speech' beyond ~200 ka ago to over ~20 Ma ago, a difference of two orders of magnitude."

So that means that at least from a mechanical standpoint, our distant ancestors had the capacity for speech.  Whether their brains were developed enough to say anything particularly interesting is still a matter of conjecture.  But evolution is all about minuscule gains.  Once the upper respiratory tract becomes capable of modulating sounds in a meaningful way, this puts selective pressure on the brain to refine its ability to understand and convey meaning with those sounds -- which puts pressure on the vocal apparatus to become better at producing subtle differences in sounds, and so on and so forth.  Which, as comedian Paula Poundstone notes, may not be entirely a good thing:

Be that as it may, it's a pretty cool discovery.  As I pointed out in Monday's post, it's incredible how much we can infer about our distant ancestors' appearance, culture, and abilities from evidence that would have been a closed book only ten years ago.  Our techniques for carrying out this research are only going to improve, so keep watching the journals -- my sense is that the amazing discoveries in this field have only just begun.

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This week's Skeptophilia book recommendation is pure fun, and a perfect holiday gift for anyone you know who (1) is a science buff, and (2) has a sense of humor.  What If?, by Randall Munroe (creator of the brilliant comic strip xkcd) gives scientifically-sound answers to some very interesting hypothetical questions.  What if everyone aimed a laser pointer simultaneously at the same spot on the Moon?  Could you make a jetpack using a bunch of downward-pointing machine guns?  What would happen if everyone on the Earth jumped simultaneously?

Munroe's answers make for fascinating, and often hilarious, reading.  His scientific acumen, which shines through in xkcd, is on full display here, as is his sharp-edged and absurd sense of humor.  It's great reading for anyone who has sat up at night wondering... "what if?"

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