ser-quasoid

gen-spade-wound

mus-croissant

tec-wonder

art-mckloud

sys-tnr-std-cond

tec-gellix

gen-brody

mus-eckmannpsych

art-ballast

mus-wooden-nickel

ser-infini

ser-onyx

tec-ballpill

tec-tiny

tec-hobeaux

gen-manicotti

ser-landnama

mus-pixel-western

gen-neue-world

tec-belwe

tec-burko

art-margate

ser-fk-raster

gen-modern-ombra

ser-cheee

art-ehrie

gen-fk-screamer

ser-gliker

gen-buffon

sci-american-typewriter

ser-pipa

gen-excaliber-nouveau

art-ohno-fatface

mus-basteleur

sci-pipo

ser-ohno-blazeface

sci-ameliapro

Test          

art-strike

gen-fleya

art-roberta

art-tenpoint

ser-bradley

gen-puchakhon-magnifier

ser-hybryda

art-kenwyn

ser-herbus

mus-gooper-condensed

sci-twoblock

ser-scandia-stencil

art-cako

ser-blimone

ser-bb-standard

ser-guillotine

sci-eklektyk

gen-combat

sci-microgramma

tec-twobit

mus-french-typewriter

ser-taters

ser-clip-regular

mus-churchward-marianna

art-nichrome

tec-hunter

sci-borax

tec-booty-bold

test

art-churchward-tua

arch-catalog

till-melted

mus-antique-olive

ser-separat

mus-workbench

sci-boogie-school-serif

mus-robur

ser-ceraph

test-font

till melted

sci-joe182

sci-cirgeos

tec-boecklin

tec-sudety

sys-zipper

ser-martin

ser-marvin-visions

art-gopher

ser-bb-strata

sci-herold

sci-supera-gothic

gen-mondwest

ser-twopoint

In Scientific Controversies, we tackle complex, conceptual, occasionally amorphous topics like animal consciousness and string theory. To watch is a feast. 5 Takeaways is a snack, an amuse-bouche for the mind.

In Scientific Controversies, hosted by our own Janna Levin, we tackle complex, conceptual, occasionally amorphous topics like animal consciousness and string theory. These rich, hour-long conversations take place in person at Pioneer Works, and feature big thinkers engaged in big questions. To watch is a feast. “5 Takeaways” is a snack, an amuse-bouche for the mind. Because comprehension sometimes demands—or, at the very least, appreciates—distillation, and the internet loves a listicle. Below, for the benefit of lay science enthusiasts, 

 Assistant Editor Stella Belt serves up key takeaways from a conversation between Janna Levin and bird neuroscientists Erich Jarvis and Lauren Riters. Watch their full discussion on 

1. Birds aren’t the descendants of dinosaurs—they 

Birds are the last living dinosaurs, offering a glimpse into prehistory. Modern birds are embedded in the theropod group of the dinosaur family tree, within the same bipedal category as fearsome predators like the T. Rex. Songbirds and parrots are known to have evolved from the monstrous “terror bird,” a giant towering at 10 feet tall.

Could other dinosaurs sing, like birds do? Possibly. Learned vocalization evolved separately among birds and humans, so it’s possible that other species developed it, too. Regardless, language and speech are rare because they attract attention. A singing species has to be an apex predator of sorts (or at the very least, smart enough) to survive. All vocal-learning mammals—whales, dolphins, elephants—are at the top of their food chains; except for bats, who vocalize in an ultrasonic range that most other species can’t hear.

2. Pigeons can tell a Picasso from a Monet.


Humans long mistook the smoothness of the bird brain as evidence of a feeble intellect (hence the derogatory expression). The consensus was that the vastly increased surface area granted by our cranial folds gave us an unparalleled advantage. But avian behavior is far too complex to result from a simple mind. Most bird brains actually have twice the neurons per cubic millimeter compared to mammals, and songbirds have four times that neural density. 

organized differently than ours, it has many of the same neurochemicals. And their visual systems are far superior, with four cones (cells in the retina) to our three. Their capacities for visual memory are incredible, too: shockingly, pigeons can learn 700 different paintings and differentiate between artistic styles, remembering individual pieces better than humans do.

The Truth About Bird Brains

3. If you can talk you can sing. If you can sing you can dance. 


Only vocal learning species can learn how to dance. In birds and humans alike, vocal pathways are embedded in the brain regions that control movement, allowing us to synchronize our movements to rhythm. When the pathway that hears sound is rapidly integrated with the one that produces it, this contaminates the rest of the motor system, meaning that other muscles start moving to the music, too. This is epigenetic, meaning the DNA is pre-existing, but gene expressions are “turned on” when birds and humans sing and release oxytocin.

Birds Sing (and Dance!) Because It Feels Good

All vocal learning species must be raised by parents of a sort, because their skills require nurturing, listening, and models to imitate. Researchers discovered that birds learn songs from adult tutors, though they can typically only learn the melodies of their own kind. As languages are passed down through generations, it turns out that different birds of the same species can develop regional dialects.

In a cowbird study, an Oklahoman flock of males was moved to Indiana and housed with a native female. The researchers figured that the midwesterner would want to mate with her new southern companions, but she seemed disinterested. Despite being outnumbered, she didn’t assimilate to their ways, nor did she adjust her taste—rather, all the Oklahoman males began to sing Indianan carols to attract her. Perhaps among birds, opposites don’t attract. But geography clearly shapes the character of their communities, informing the way individuals speak, sing, and even who they desire.

Birds sing to attract mates and defend territories, but they also sing simply because it feels good. New York City’s skies fill with song in the spring, as seasonal breeders time their flirtations to match resource availability. Some birds take in daylight through their skulls rather than their eyes, allowing sun to reach deep brain structures and produce sex hormones in the warmer months.

While dopamine is partly responsible for reward-related processes, endogenous opioids (like heroin and fentanyl, but 

) play a strong hand in facilitating bird song, too. 

If you stimulate avian opioid receptors, they sing at high rates—but they aren’t singing mating songs. In fact, differences in song function can be intuited from the fact that they’ll stop singing altogether if you interrupt their romantic melodies with a dope hit. Breeding leads to an endogenous opioid release, so males will halt their tunes once they’ve received it. And as they practice in the fall, their songs are rewarded by a low-level endogenous release, which triggers different brain patterns than when they’re singing to attract a female. Alone, they’re able to explore different melodies without chasing an ideal, as we might while singing in the shower. And if you take a bird to a certain spot and let it sing, studies have shown that it will develop a strong attachment to that venue. ♦

5 Takeaways: Birdbrain

In our science programs, hosted by Janna Levin, we tackle complex, conceptual, occasionally amorphous topics like animal consciousness and string theory. These rich, hour-long conversations take place in person at Pioneer Works, and feature big thinkers engaged in big questions. To watch is a feast. “5 Takeaways” is a snack, an amuse-bouche for the mind. Because comprehension sometimes demands—or, at the very least, appreciates—distillation, and the internet loves a listicle. Below, for the benefit of lay science enthusiasts, the 

 editors serve up key takeaways from a conversation between Janna Levin and Venki Ramakrishnan. Watch their full discussion on 

Death may come for us all, but that doesn't mean it's programmed into our genes. Aging isn't a built-in shutdown sequence—it's the gradual result of wear and tear over time. Evolution favors traits that help us survive long enough to reproduce, but it has little interest in what happens afterward. Ironically, the same genetic traits that ensure our early survival often contribute to our decline later in life. Still, there are no genes made to age us. Death is simply the biological cost of being alive.

2. We live longer, but we don’t get older.

In the last 150 years, life expectancy has doubled, but the maximum human lifespan hasn’t budged much. The oldest person that ever lived is Jeanne Calment, who died at the age of 122 in 1997. She smoked for all but the last five years of her life, and ate more than two pounds of chocolate every week. She lived in Arles, the town in southern France where van Gogh resided near the end of his life. When she met the artist in her teens, she described him as “very ugly, ungracious, impolite, and sick.”

Despite her charms, it’s unlikely Calment was more than a genetically blessed miracle. Her habits aren’t lessons to emulate—sadly, there’s no evidence that chocolate will protect you from an early grave. No matter the advances in science and improvements in public health, nobody’s beaten her record of life in the 25 years since she died. We may be better at avoiding early death as a species, but we’re still not breaking the ceiling.

3. Your body dies, but your cells (kind of) don’t.

All of us came from an unbroken chain of living cells that stretches back billions of years. Your cells are therefore part of an immortal lineage, just renting your body for a while. You’re a disposable vehicle for ancient self-replicating molecules—which will survive so long as life continues on Earth.

Still, when we think of death, we’re generally thinking about our own: the end of our conscious existence as an individual. But if there’s a direct line of succession from us to our ancient ancestors, there is something about each of us that 

die. Our cells outlive our body by developing into our children and resetting the biological clock every time we procreate—babies always start at zero, no matter the age of their parents. Individuals die, but life goes on without end.

4. There’s a jellyfish that ages in reverse.

The probability that anyone will die tends to increase with age—but there’s one species of jellyfish whose chance of death never changes. When the 

 is faced with injury or stress, it metamorphoses into an earlier stage of development and lives its life all over again. Gerontologists may salivate at the possibility that these creatures are biologically immortal—but according to Venki Ramakrishnan, their regenerative capacities make them more like trees than us.

Progress in science isn't just about data—it's about funerals. People don’t discard false ideas and adopt new ones because they’ve changed their minds. Rather, scientists just die, and a new generation is able to look at the data more objectively. 

In other words, science advances one funeral at a time. Old ideas don’t fade quietly, they just die with the people who cling to them. ♦

A window display of various wooden coffins and caskets for sale at a funeral director's office in Warsaw, Poland.

5 Takeaways: Death

In Scientific Controversies, hosted by our own Janna Levin, we tackle complex, conceptual, occasionally amorphous topics like animal consciousness and string theory. These rich, hour-long conversations take place in person at Pioneer Works, and feature big thinkers exchanging on big questions. To watch is a feast. “5 Takeaways” is a snack, an amuse-bouche for the mind. Because comprehension sometimes demands—or, at the very least, appreciates—distillation, and the internet loves a listicle. Below, for the benefit of lay science enthusiasts, leading astronomy journalist Stuart Clark serves up key takeaways from a conversation on the 

between Wendy Freedman and John Mather, clips of which we've sprinkled throughout.

What’s with the buzz about this thing called JWST?

is the largest telescope we’ve ever sent into space. A joint effort between NASA, the European Space Agency (ESA), and the Canadian Space Agency, the telescope is so big, it had to be folded origami-style into the nose cone of ESA’s Ariane 5 rocket. Weeks after its launch on Christmas Day, 2021, NASA engineers and enthusiasts everywhere held their collective breath as the JWST successfully completed a series of maneuvers, with numerous single points of failure, each of which could have doomed the mission. Soon after separating from the rocket, it deployed its solar array and sped towards a special place in space called the second Lagrange Point (L2), almost a million miles from Earth. During the first week of its journey, JWST opened its sunshield, a tennis court-sized barrier that shelters the telescope from the heat of the Earth and the Sun. Made of five layers of polymer material, each about one thousandth of an inch thick each, the sunshield had to unfold perfectly, with no snags or tears. And it did. Its purpose is to create a temperature difference of about 570 degrees Fahrenheit between its sunward side and the telescope’s optics and instruments, which work in its shade. The JWST took a month to reach L2, at which point it had deployed its telescope tower, and the primary and secondary mirrors, all while powering up its instruments. At 6.5 meters across, the JWST’s primary mirror is now the largest telescope mirror in space.

John Mather on the Unfolding of the James Webb Space Telescope

It has 6.25 times the light collecting area of its predecessor, the 2.4-meter mirror of the Hubble Space Telescope (HST). Also, unlike the HST’s monolithic mirror, the JWST’s mirror has eighteen hexagonal elements, each made of ultra-light and stiff beryllium. JWST unfolded its mirror as it flew to L2, and once it arrived, NASA engineers aligned these hexagonal elements to a precision of about ten-thousandths of the thickness of human hair. This allows them to act as a single, large mirror. The mirror’s size, and the chill afforded by its sunshield, means that the JWST can observe light at infrared wavelengths. Compared to the HST, which sees mainly in optical wavelengths, JWST can detect cooler objects. Since infrared light can go through dust, much like X-rays through bodies, the JWST can peer through dust clouds, which often harbor newly-forming planets and stars. It might even see some of the earliest objects that formed in our universe, because the cosmos’ expansion would have stretched the light from these objects into JWST’s infrared range.

Hubble Deep Space vs. James Webb Field Image

Why should astronomers study these earliest objects?

Scientific curiosity, for one. JWST is designed to look for the first objects that formed a few 100 million years after the cosmic microwave background (CMB) radiation, the big bang’s fossil radiation, flooded the universe. Were these objects stars or galaxies or black holes? JWST should see the first glimmers of such objects and thus help answer an astrophysical mystery: how did the supermassive black holes that we see today at the center of most galaxies get so big so quickly? Did they start forming soon after the big bang, or did they arise from processes we don’t yet understand? The JWST will look for the potential seeds of these supermassive black holes. Finding them could give astrophysicists further insights into the formation of galaxies, in particular, and the general evolution of structure in the universe.

What the James Webb Space Telescope Tells Us About Black Holes

What else can such observations tell us about the universe?

The JWST will also help solve another mystery that’s been exquisitely set up by the Hubble Space Telescope. Before the HST was launched in 1990, astronomers were struggling to put bounds on something called H0 (read that as “H-naught”), the Hubble constant—a single number that tells us how fast the universe is expanding today. Calculating this number requires precise measurements of the distances to objects such as Cepheid variable stars and type IA supernovae. Before HST, estimates of H0 varied wildly, landing anywhere between 50 and 100 kilometers per second per megaparsec. The HST’s observations have helped astronomers pin this number down to 73.04 ± 1.04. But an entirely different method, using precise observations of the cosmic microwave background, gives H0 to be 67.49 ± 0.53. Either one of these estimates is wrong or we are missing something crucial in our understanding of the universe and its evolution. The JWST will help resolve this debate by studying so-called red-giant-branch stars, which are stars at the end of their lives that have expanded and cooled somewhat. JWST will accurately measure the luminosity of such stars, which will help astronomers calculate the distance to galaxies that host these red giants and make a more precise estimate of H0.

James Webb Space Telescope Images of the Ring Nebula

Is there anything close by that the JWST will set its sights on?

Yes, among its targets are exoplanets in our own galaxy. The JWST has the instruments to analyze the spectrum of starlight that filters through the atmosphere of planets orbiting other host stars. The spectrum can tell astronomers about the chemical elements in the planet’s atmosphere: is there water, or carbon, or oxygen, or methane, for example? Already, the JWST has found carbon dioxide and sulfur dioxide in the atmosphere of WASP-39b, a Saturn-sized planet orbiting a star about 700 light years from Earth. JWST will soon study a system of seven rocky, Earth-sized planets orbiting TRAPPIST-1, a red dwarf star that’s a mere 40 light years away. A number of these planets could be potentially habitable. So even as we marvel at JWST’s ability to look deep into the distant past, its most momentous discoveries may come from closer to home. ♦

Stuart Clark is an astronomy journalist and author of several books about space, both non-fiction and fiction, including 

James Webb Space Telescope

5 Takeaways: James Webb Space Telescope

In Scientific Controversies, hosted by our own Janna Levin, we tackle complex, conceptual, occasionally amorphous topics like animal consciousness and string theory. These rich, hour-long conversations take place in person at Pioneer Works, and feature big thinkers exchanging on big questions. To watch is a feast. “5 Takeaways” is a snack, an amuse-bouche for the mind. Because comprehension sometimes demands—or, at the very least, appreciates—distillation, and the internet loves a listicle. Below, for the benefit of lay science enthusiasts, contributor Anil Ananthaswamy serves up key takeaways from a conversation on 

 between guests Yann LeCun and Max Tegmark.

Artificial Intelligence (AI) refers to software or hardware that attempts to mimic human intelligence in ways small and large. The current approach to building AI involves machine learning, in which computer systems learn about patterns in data, and then use this knowledge to make predictions about new data and take actions. An email spam filter, for example, uses machine learning: it examines a large sample of emails that have already been annotated as spam or not-spam and figures out patterns that typify spam. It then uses this knowledge to filter out spam from future emails, while continually learning to keep abreast of new tactics by spammers. Such machine learning systems have been extremely successful at tasks such as face and speech recognition, and language translation.

Current AI systems are good at specific tasks: image recognition, for example. Such AI is called weak or narrow AI. The effort is ongoing to develop artificial general intelligence, or AGI, which refers to AI that will ostensibly match or even exceed human intelligence, in that it’ll be capable of thinking and tackling a wide variety of problems, even those that it wasn’t explicitly trained to solve. Some worry that AGI will eventually become supremely intelligent and autonomous and pose a threat to human existence. But whether this will happen, let alone exactly when, is a topic of intense debate. Scientists also differ in their opinions about when we should start planning for such an eventuality. Some advocate that now is the right time, while others argue that we should wait until we know what such an AGI will look like.

Maybe. Certain materialist philosophers assert that humans are material beings and that everything about us—including our consciousness—can eventually be understood as the outcome of the interactions and organization of matter that comprises our brains and bodies. In this way of thinking, everything—from the tiniest to the most complex of lifeforms—is made up of a hierarchy of interacting systems built from the bottom up; and the mind—both the conscious and unconscious aspects of it—is the outcome of such machinery. In other words, we may be biological machines.

Could machines become sentient, and how could we tell?

If the materialist philosophers are correct—and that’s a huge 

—then our subjective feeling of consciousness as something non-material is simply an illusion. If so, it’s possible that we will one day build machines that will have similarly subjective experiences of consciousness. To tell whether or not a machine is conscious, we’d have to design a suitably aggressive Turing Test. Such an aggressive test would probe a machine’s claims of internal conscious experience to gauge if it is truly intelligent. Also, if neuroscience deciphers the brain processes that give rise to the illusion of subjective consciousness in humans, then we could simply look for similar processes at work in machines.

Is intelligence limited to carbon-based life?

Not necessarily. Carbon, it turns out, is an excellent element for engendering life. Each carbon atom can chemically bond with up to four other atoms, enabling the formation of biologically important long-chained molecules such as proteins and DNA. Carbon is the substrate of life on Earth. But there is no reason to think that machinery built out of other elements, such as silicon, cannot be imbued with intelligence and consciousness; there is no scientific basis for carbon chauvinism. Artificial general intelligence built using software and hardware could one day demonstrate that properties considered the purview of carbon-based lifeforms may indeed be substrate-independent. ♦

Anil Ananthaswamy is an award-winning journalist and author of

Artificial Intelligence

5 Takeaways: Artificial Intelligence

In Scientific Controversies, hosted by our own Janna Levin, we tackle complex, conceptual, occasionally amorphous topics like animal consciousness and string theory. These rich, hour-long conversations take place in person at Pioneer Works, and feature big thinkers exchanging on big questions. To watch is a feast. “5 Takeaways” is a snack, an amuse-bouche for the mind. Because comprehension sometimes demands—or, at the very least, appreciates—distillation, and the internet loves a listicle. Below, for the benefit of lay science enthusiasts, contributor Anil Ananthaswamy serves up key takeaways from two conversations: one on 

, with guests Elena Aprile and Peter Fisher, and another on 

, with guests Rachel Rosen and Pedro Ferreira.

The universe has a dark sector. What is it?

It’s easier to start with what it is not. It’s not normal matter, which is everything that’s familiar: we and all life on Earth, the solar system, the Milky Way, the hundreds of billions of stars in our galaxy, the hundreds of billions of other galaxies in the universe, and the gas and dust strewn across intra-galactic and intergalactic space, all of it, down to the last elementary particle. This normal stuff makes up about five percent of the universe. The other 95 percent comprises the dark sector, named so partly because we don’t know its exact nature and partly because it doesn’t interact with light—which technically makes it invisible, not dark. The dark sector has two major components: dark energy and dark matter.

Why do we think there’s dark matter out there?

Astronomers have known since the late 1930s that something was amiss about the speeds at which galaxies move around in clusters, or the speeds at which stars and gases rotate about the center of a galaxy. Given the gravity of the discernible, luminous matter, the cosmic objects should be moving much slower than they are. By 1970, astronomer Vera Rubin had accurately measured such anomalous speeds in the nearby Andromeda galaxy. Her observations suggested that the gravity of an unseen mass was holding the galaxy together, preventing it from flying apart. This unseen mass has been termed dark matter. It doesn’t interact electromagnetically with normal matter, meaning it doesn’t emit nor engage with light. Multiple methods of estimating the amount of dark matter show that it makes up about 27 percent of the universe.

We don’t know. Astrophysicists once thought that dark matter could be non-luminous normal matter that’s hard to see. These would include: black holes; or neutron stars, which are the collapsed cores of supergiant stars; or brown dwarfs, which are small stars that cannot sustain the nuclear fusion needed to emit stellar light. These are collectively called massive astrophysical compact halo objects (MACHOs). Astronomical surveys, however, failed to find anywhere near enough MACHOs for them to be dark matter. Now, physicists, for theoretically plausible reasons, think dark matter is most likely made of particles known as weakly interacting massive particles (WIMPs), which would interact with normal matter only via the weak nuclear force and gravity. Efforts to create such particles at the Large Hadron Collider (LHC) at CERN near Geneva, Switzerland, have failed. It’s possible that their mass is beyond the reach of the LHC, and creating them would require more powerful particle smashers. Also, efforts to detect potential collisions of dark matter particles with nuclei of normal matter using ultra-sensitive detectors housed in deep underground mines have also failed. But the circumstantial evidence that dark matter exists is so strong that cosmologists continue to look for any clues as to what it might be.

If dark matter poses problems, dark energy compounds them. Through the 1980s and ’90s, cosmologists studying the expansion of the universe were expecting to find that spacetime had been steadily expanding for about ten billion years after the big bang, but this expansion would eventually have been reined in by the gravity of all the matter in the universe. But instead of slowing down, the universe’s expansion seems to have started accelerating about four to five billion years ago. Mostly, physicists attribute this to the inherent energy of spacetime, and call it dark energy. As the universe expanded, the amount of overall dark energy increased beyond a certain threshold, causing spacetime to blow apart—in a manner of speaking. Plug in the right amount of dark energy and dark matter into Einstein’s equations of general relativity and you can accurately model the universe’s observed initial unhurried expansion and then its recent acceleration. In today’s universe, dark energy makes up about 68 percent of the cosmos.

For starters, dark energy seems to have just the right value, in terms of the amount of energy per unit volume of space. Had it been less, the universe would have long since collapsed due to the gravity of matter; any greater and the universe would have blown apart before the stars and galaxies and planets could form, let alone intelligent planetary life pondering the mysteries of the cosmos. Physicists struggle to explain why dark energy has the value it does. It frustrates them that they cannot derive it from first principles. Also, quantum physics says that the emptiness of spacetime is not really empty: it’s a froth of virtual particles that constantly appear and disappear; this process gives spacetime an energy that’s about 120 orders of magnitude (=10

, or a trillion raised to the tenth power) greater than the observed value of dark energy. Something isn’t adding up. That’s why almost all the current and planned cosmological and astrophysical surveys of the cosmos are focused on deciphering the dark sector. ♦

Anil Ananthaswamy is an award-winning journalist and author of 

Dark Matter + Energy

5 Takeaways: Dark Matter + Energy

In Scientific Controversies, hosted by our own Janna Levin, we tackle complex, conceptual, occasionally amorphous topics like dark energy and string theory. These rich, hour-long conversations take place in person at Pioneer Works, and feature big thinkers exchanging on big questions. To watch is a feast. “5 Takeaways” is a snack, an amuse-bouche for the mind. Because comprehension sometimes demands—or, at the very least, appreciates—distillation, and the internet loves a listicle. Below, for the benefit of lay science enthusiasts, contributor Anil Ananthaswamy serves up key takeaways from a 

 between Janna and neuroscientists Anil Seth and Joseph LeDoux on the body, brain, and consciousness.

Well, that’s a tough question. There are probably as many answers as there are philosophers and neuroscientists theorizing about consciousness. To help keep our feet planted on scientific ground, let’s talk about consciousness as the brain-generated subjective experience of something, anything: the smell of a flower, the color of the sky, even the feeling of being someone with a body and a story. You could imagine building a robot with today’s technology that has the sensors to sense the electromagnetic spectrum of the sky. Does it have an internal experience of the sky being blue on a clear winter’s day? Very likely not. But we do. Let’s call that a conscious experience. It doesn’t matter what one is conscious 

; the contents of one’s consciousness aren’t important. The subjective feeling, the experience of that content, can be attributed to consciousness.

Because each one of us is a distinct individual with a distinct body and brain. The brain has no direct access to the world outside or even to the rest of the body, except via the information carried by nerves from within the body and without. The brain has to infer what’s out there based solely on such incoming information. Computational neuroscientists think that the most efficient way for the brain to make such inferences is by predicting the external causes of incoming information, using internal models it builds of the body and of the environment. These predictions are what we perceive, consciously or otherwise. Let’s say you and I are looking at a rose. Firstly, each of our brain’s predictions of the rose’s redness may not tally with objective reality. Also, because our brains are different, in their wiring and biochemical makeup, their predictions will likely differ ever-so-slightly. We just agree to call the rose ‘red’; we have no idea if we are talking of the same kind of redness. Also, the experience is being had by an experiencing self. So, in all these ways, it’s subjective.

The self is another thorny word, with myriad meanings. We can start by distinguishing the self from self-consciousness, which is the awareness of being a self. Let’s worry about the former; the latter can be understood as some higher order outcome of the former. The basic self is best thought of as the entity that experiences. Again, the exact experience is not important: it could be a color, a sound, or pain in one’s left foot. But in all cases, there seems to be an entity experiencing it. So, the self, in its stripped-down form can be thought of as the subject of an experience. Of course, then the question arises: is such an experiencing entity itself a construction or prediction? Some neuroscientists think so. It might be that it’s the outcome of an internal model or self-schema built by the brain.

Do animals have selves and are they conscious?

Opinions vary. Before talking of animals, consider the Roomba scuttling about in your living room. It certainly has a self-model, meaning a model of its shape, size, speed, etc. situated within an internal model of the room. Almost no neuroscientist or philosopher in their right mind would say that the Roomba is conscious or has self-consciousness. But such statements become blurrier when talking about apes, dogs, cats or more primitive animals. Given that animals navigate physical spaces and survive, they most certainly possess a self-model. They are also most likely conscious, but the contents of their consciousness—meaning what it feels like to be a cat or a dog or a bonobo having some experience—will be different from ours and indeed from each other’s. Self-consciousness, however, is harder to pin down; the great apes are almost certainly self-aware. Opinions begin differing when considering other animals. And then there are octopuses, with a highly distributed nervous system; their behaviors have all the hallmarks of highly intelligent, conscious beings. No one disputes their intelligence, but are they conscious? The honest answer: we don’t know.

How can we tell if an animal is conscious, or has a self?

It’s well-nigh impossible to tell if an animal is conscious. For that matter, we cannot be sure of each other’s consciousness. Maybe one day there will be an objective measure of consciousness, based on brain activity. For now, we can agree that humans are conscious beings, because we can say so to each other. Interrogating the presence of a self is somewhat easier, but only just about. There’s the mirror self-recognition (MSR) test: while an animal is under anesthesia, an experimenter puts a colored dot on the animal’s forehead. When the animal comes to, it’s shown a mirror. If it recognizes in the mirror a reflection of itself, the animal will touch its forehead and the dot, maybe even remove the dot. If it does so, it clearly has a form of self-awareness. A handful of species pass the test, including the great apes, dolphins and a species of magpie. Most fail the test. But the MSR test is controversial. For starters, a mark on the forehead may not elicit the desired response simply because the mark isn’t threatening. So, failing the test doesn’t imply lack of self-awareness; it just means that the animal couldn’t be bothered. Also, MSR only tests for whether or not animals have visual self-awareness. Maybe most don’t. Maybe they use other sensory information, such as smells or sounds, to construct self-models and distinguish themselves from others. Simply put, consciousness and the self remain enigmatic. ♦