Ben Henry: You’re listening to Consilience, a podcast from The Scientist magazine. This month, we’re bringing you stories about music and the brain. I’m Ben Henry.

Our first story is about why we like the music that we like. To help me untangle the research on this topic, I’m talking with Diana Kwon, a staff writer for The Scientist magazine. Diana, thanks for talking with me.

Diana Kwon: Thanks for having me.

BH: So, you wrote a piece in the March issue of The Scientist called “Musical Tastes: Nature or Nurture.” That story starts in the late nineteen nineties, with a study by two Harvard psychologists, Marcel Zentner and Jerome Kagan, who wanted to know whether four-month old infants preferred consonant musical chords over dissonant ones.

DK: From my understanding it’s the first time somebody actually sat down and said: Okay, let’s take some babies and see what type of music they like.

BH: What they would do is sit a baby down in front of a speaker. They played each kid two versions of a melody. One version contained consonant chords, a combination of notes that just sound nice together [C major plays]. The other version had slightly different chords that sound a little bit grating [C diminished plays]—dissonant chords.

Zentner and Kagan found that these very young children didn’t appear to like the dissonant music: they were fidgety, they wouldn’t look right at the speaker, they would cry. But when the consonant music played, they were much more likely to just sit contentedly and listen.

DK: And since then, researchers have done a bunch of other studies on kids who are even younger, and even in animals like chimps and baby chickens, and have found similar things. There’s just been increasing evidence building that maybe there’s some sort of preference at an early age.

BH: We think of our musical preferences as being highly personal and subjective. But maybe, some part of it is actually biologically hardwired in us.

Diana spoke to Josh McDermott, who studies this idea at MIT. Here’s a piece of that interview. He’s explaining another reason why we might have an ingrained preference for certain intervals, that is, combinations of notes.

Josh McDermott: I think it comes down to the fact that the particular intervals that are used in Western music, and arguably in music cross-culturally, are not random. The intervals that are most common, or most important, in Western music are typically defined by ratios between the pitches that are simple integer ratios, or approximately so.

So they’re not random, and so that seems to indicate, well, there’s got to be some force that’s responsible for the fact they’re not random. And so one possible force is that there’s an intrinsic aesthetic difference between different musical intervals, so people end up using the ones that are more pleasing.

BH: The problem with this argument, that there’s something inherently nice about certain combinations of notes, is that almost all of the studies supporting this idea took place in Western cultures, where we share a musical heritage. From classical music hundreds of years ago to radio hits today, we rely heavily on consonant chords and avoid dissonant ones.

So, maybe we’re just biased, and the infants in those studies absorbed just enough Western music to show that bias.

To get around that problem, McDermott joined a group of anthropologists and other scientists studying a group of people who don’t listen to Western music—or for that matter, any music other than their own.

The Tsimane’ live in a vast, remote swath of the Bolivian Amazon. They’re mostly isolated from surrounding cultures. McDermott and his colleagues wanted to know if they had the same aversion to dissonance that we do. Here’s McDermott again.

JM: The first part of the trip that summer, we did a bunch of recording sessions with the Tsimane’ musicians, so that was pretty fun and quite interesting. So we set up a little recording studio as best we could in this one building in this town. A few weeks before we arrived, we arranged for there to be a big announcement broadcast that we were looking for musicians. They just started showing up—some of them had traveled days basically to come hang out and play music.

BH: The music the Tsimane’ played for them sounded fabulously unlike anything you would hear on the radio.

So McDermott’s team had this unique opportunity to study people whose musical experience was completely different from those of us raised in Europe or North America. Diana can explain the experiments they did.

DK: What they would do is—kind of like what the researchers would do back in the nineties—they would play clips of music, and because they were adults they were able to just ask them whether they preferred one piece of music to another. Another important thing they needed to do was figure out whether this group of people could tell the difference between these two different types of tones.

BH: McDermott and his colleagues found that the Tsimane’ were perfectly able to tell the difference between consonant and dissonant sounds. But when they were asked to rate those clips of music on a scale according to how much they enjoyed it, they gave consonant and dissonant music the same ratings.

Unlike Westerners, the Tsimane’ didn’t have an ingrained distaste for dissonance. But the story is complicated, McDermott says.

JM: One cautionary note I would provide is that most people, myself included, would shy away from these black and white distinctions between being innate and learned. A lot of people would say nothing is completely innate . . . and in my mind, there’s a real vacuum in terms of having good experiments in pretty remote cultures.

BH: Even if we’re all born with a preference for consonance, the Tsimane are evidence that it can be overruled by culture. If there is something truly universal about musical tastes, we haven’t found it yet.

LJ Rich: I never listen to music voluntarily. I hear music everywhere, whether I like it or not. You see, I have this strange mixing of the senses called synesthesia.

BH: Synesthesia. That’s the subject of our next story about music and the brain. This is technology journalist and composer LJ Rich giving a TED Talk in 2014.

LJR: When I see, touch, or taste things, I hear sound. And when I hear sound, I hear music—My brain generates music. It’s really useful when I’m doing classical composing. However, it does mean that, in my other, day job as a TV reporter for BBC Click, the technology show, it can get a little overwhelming. I get distracted by reality.

BH: At this point, Rich walks over to a keyboard on the stage.

LJR: I’m going to let you into a secret, and explain why I’m so distracted. Going around a building, or going around a city, I kind of hear this. These are the cars. The buildings are kind of like this, and the people are kind of like this.

BH: There’s something else going on here. LJ Rich is not only a synesthete, she also has absolute pitch, meaning she can identify or play any given musical note by ear, without any sort of reference. Between these two gifts, her whole world is music.

LJR: It’s so overwhelming, that the way that I deal with it is by harmonizing with it. I make noises, I sing along, I probably look a little crazy when I do it. But it turns that noise into music.

BH: It seems like a total coincidence that Rich has both synesthesia AND perfect pitch—But it’s not. I’m talking with Catherine Offord, who wrote about this in the March issue of The Scientist. Hi Catherine, thanks for talking.

Catherine Offord: Thank you very much for having me.

BH: You spoke to LJ Rich about what her world is like and also about the neuroscience behind it. Before we even get into that, it’s just so hard for me to even imagine what living inside of her head feels like.

CO: Yeah, and it’s something she’s aware of as well. She was telling me that it’s difficult to have conversations with people because you want to use words like delicious, or tasty, to describe sounds. To somebody who doesn’t have synesthesia, that just sounds like you’ve made a bit of a slip-up.

BH: Can you just summarize, in general, what synesthesia is?

CO: Synesthesia is the linking of different senses when you get one stimulus. So for example, you have a taste, and that’s associated with a sound, or you see a word, and that’s associated with a color. So it’s basically crossing over these different sensory inputs.

BH: From your reporting, it sounds like there’s a lot more going on here. What have you learned?

CO: So, first of all, I wanted to chat with some people at the Feinstein Institute. They’d been conducting a study a few years ago where they managed to find all these people—hundreds of people—with absolute pitch. And they’d given them a few surveys to find what other kind of experiences they might be having. They discovered that around 20 percent also had synesthesia.

BH: Twenty percent—that’s not necessarily true of all people with absolute pitch; this was just one study after all—but it’s still a huge proportion, considering that synesthesia is relatively rare in the general population.

CO: That kind of led them to look at this overlap, between absolute pitch and synesthesia.

BH: That’s where LJ Rich comes in—she’s part of this overlap.

Another team of researchers, led by Psyche Loui of Wesleyan University, used MRI machines to compare the neural activity of people with synesthesia and people with absolute pitch. 

CO: They were finding, first of all, that the neural activity was kind of unusual in both groups. So both had this heightened neural activity known to be involved in processing music. But in the people with absolute pitch, there was more activity on one side, and in synesthesia, there was more activity on the other side. And so they had this little phrase that they coined in the title of their paper, which was that maybe these things are just two sides of the same coin.

BH: On one side of the coin: the ability to perfectly, and consistently identify any musical note, just by hearing it. On the other side: a world of bright sounds and loud shapes.

The two seem to have nothing to do with each other. But there’s a theory out there, that all of this has to do with a neurological concept called hyperconnectivity.

One of the ways that researchers can quantify what the brain is doing is to track the connections between different parts of the brain. A neurological roadmap keeps all of the separate parts connected to each other. But researchers have noticed, some people have more roads on their maps than others. When one part of their brain is active, it’s more likely to cause some other part of their brain to be active, sometimes parts that would normally be resting. That’s hyperconnectivity.

The concept shows up in a lot of different types of research. For example, studies have suggested that hyperconnectivity might explain some cases of depression. They’ve linked it to autism, and even schizophrenia.

Those brain scans of people with perfect pitch or synesthesia turned up a similar suggestion.

CO: Perhaps, heightened connectivity is partly leading to these extra modes of perception, like absolute pitch, or synesthesia, or extreme creativity, or things like that.

BH: It’s still a hypothesis, but maybe studying the brain’s connections could help us understand incredible gifts as well as disease. There’s another application to this field of research.

CO: Although this isn’t a disease—it’s not as though absolute pitch or synesthesia can be thought of as a disease model—it is a really great model for the interaction between genes and the environment. Because there is evidence that suggests that things like absolute pitch and synesthesia don’t necessarily come about just because of your genetics. So, it seems there are things early in life or during development that can make it more or less likely that someone will develop synesthesia and absolute pitch. And so they think it’s a really good model to use to study those overlaps.

BH: For now, the mind of LJ Rich is mostly a mystery.

Before we end the episode, we have one more interesting tidbit about the brain. I heard about this from Bob Grant, a senior editor at The Scientist. Here’s our conversation.

So, you were telling me that you were reporting a story about bats, but you had sort of inadvertently uncovered some surprising information about birds. So, what did you learn?

BG: Yeah, so I was talking to a guy at Texas A&M named Mike Smotherman who has studied bat song for quite a while, and now he’s transitioned and out of that. So I was kind of just talking with him about research, current research that’s uncovering some similarities between the neural substrates that drive bird song and bat song. There’s a couple different instances where some of the same brain regions give rise to the vocalizations, et cetera, et cetera.

What he told me was—and he said it in kind of a matter of fact way: You know how song birds regrow a part of their brain during the spring so that they can sing their mating songs, and then that part dies back, and then regrows again the next spring when they need to sing again? And I was like—wow—I didn’t know that.

BH: Out of curiosity, Bob looked into why a bird might lose and then regrow a part of its brain every year.

BG: Brains are very energetically expensive things. To run a brain, to maintain a brain, takes a lot of energy. A lot of the energy that human beings for example consume goes to the maintenance and running of our brains. So it makes sense, from an evolutionary perspective in these birds, that when it’s essential that they display this behavior, for the furtherance of their species and their population, that they grow that brain center to produce these songs.       

It’s interesting in and of itself, but it also was one of the first insight into neurogenesis in vertebrates that made people think—oh, wait a second, this old dogma where you’re born with the neurons you have, especially in the brain, and if you lose ‘em you lose ‘em. That dogma has changed over the past few years, to where people realize that neurogenesis is a real thing that happens in vertebrates and mammals, and humans even.

BH: So there you have it. We shut off the heat when we go on vacation, and some birds lose a part of their brain when they don’t need it.

That’s it for Consilience this month, the show is written, produced, and edited by me, Ben Henry, with help from Kerry Grens, Bob Grant, and Jef Akst. We’ll be back in April.