What are the structural differences in the brain between animals that are self-aware (humans, apes) and other vertebrates?
—Emma Schachner, Salt Lake City
Robert O. Duncan, a behavioral scientist at York College, the City University of New York, responds:
Self-awareness distinguishes humans from most other species. In psychology, self-awareness is defined as metacognition, awareness of one’s own ability to think. In humans, metacognition and other advanced cognitive skills, such as social intelligence, planning and reasoning, are all thought to depend on a region of the brain called the prefrontal cortex.
If we assume that the prefrontal cortex permits metacognition, then the answer is simple: species that fail to demonstrate metacognition tend to lack brain areas that resemble the prefrontal cortex. But because this area serves many cognitive functions and is well connected to the rest of the brain, the region is probably not the sole locus of metacognition. In other words, the prefrontal cortex may be necessary but not sufficient for self-awareness. Some psychologists speculate that self-awareness may arise in animals with greater overall cognitive ability, larger brain size or a higher degree of connectivity among brain areas.
Identifying the precise structural differences that make some creatures self-aware and others not is quite challenging. Most important, it is difficult to pinpoint and compare subtle structural differences across species in the face of more dramatic differences in brain morphology. For example, dolphins and chimpanzees both demonstrate metacognition, but their brains look completely different.
Additionally, simply identifying which species exhibit self-aware behavior has proved tricky because no reliable behavioral tests for the trait exist. In 1970 Gordon G. Gallup, Jr., of the University at Albany, S.U.N.Y., developed the “mirror test” to assess metacognition in chimpanzees. A chimp passes the test if it uses the mirror to inspect a mark that has been painted on its face. Although the majority of chimps pass, some do fail, causing certain scientists to consider the test unreliable.
The difficulties we have assessing self-awareness demonstrate that it is a complex trait and support the idea that no single brain area is dedicated to it. Overall, the prefrontal cortex may be critical for metacognition, but self-awareness most likely emerges when this region is highly interconnected with the rest of the brain.
Rights & Permissions
See what we're tweeting about
25 Comments
Add CommentHow would you detect whether some other organism was self-aware? The mirror test does not detect this; it detects that an organism is both self-aware, and able to abstractly recognize that the image in the mirror is a reflection of itself. It is possible that a creature is self-aware without being able to realize that a reflection in a mirror is a reflection.
Reply | Report Abuse | Link to thisA mirror test is actually less than that. A robot could be programmed to inspect its body using a mirror or a camera on an arm, and that would not be an indication of self-awareness.
Mr Duncan should elevate his Science and state some where in his response the fact that is evident from his article - that Science simply does not know the answer to this question . . . yet.
Reply | Report Abuse | Link to thisScience is not religion and should not be afraid to say 'we do not know ... yet'.
Humans; they are so good at projecting their "This-is-my-view-so-it-must-be-THE-view" notions on the rest of the world! An amoeba has no social skills (or libraries) so they cannot possibly be self-aware. In another view, sentience goes down all the way to viruses, and relieves nothing/no entity of consequences. "This leaf is just a plant, so there are no consequences to its sense of self if I destroy it, consume it." Because it is a Human perspective, it must be the superior choice, the right thing. Homo Sapiens; a temporary bump in the fabric of evolution; better luck with the next model!
Reply | Report Abuse | Link to thisIt seems it should be more about rights of existence that establish any hierarchy than abundances of proofs of self-superiority. Perhaps this was funded by the beef industry, that cannot afford to EVER have cows seen as self-aware! OMG!
i hate the thought of killing and eating something that is self aware, so come on science and chemistry give us more non-sentient goop from the lab for food.
Reply | Report Abuse | Link to thisI agree with your sentiment, but it should also be considered that many if not all living creatures in some way experience pain. Whether or not the creature is self aware, killing it causes it pain. However, this is the way life, and I sure do love a good steak & potatoes, or fish & rice - the less I know of what they knew the easier it is to swallow...
Reply | Report Abuse | Link to thisQuestion: Are other species (including humans) still evolving? Are humans stunting our own evolution by intervening with drugs and not allowing natural selection to take place? It's cruel but have humans
Reply | Report Abuse | Link to thisallowed those with genetic diseases to procreate weakening the genetic pool?
Left alone could other species become cognitive?
Interesting questions - I can't answer them, but humans have certainly affected the evolution of domesticated animals such as cattle, sheep, horses, cats and dogs. Not that they might already be cognitive had we not influenced their development, but we'll never know...
Reply | Report Abuse | Link to thisOn the other hand, all animals have to varying degree affected the development of all other animals that they interact with, especially predators and prey.
Does this article actually contain any information? It does not ultimately say more than "Metacognition basically happens in creatures that are smarter" - and that's pretty empty!
Reply | Report Abuse | Link to this"Are other species (including humans) still evolving?"
Reply | Report Abuse | Link to thisSome species are still evolving, others are not. Humans are still evolving. 10,000 years ago adult humans cannot digest milk. Now we can. This digestive ability evolved since humans domesticated animals for milk. The cockroach looks the same since it first appeared 100 million years ago. It hardly evolved.
"Are humans stunting our own evolution by intervening with drugs and not allowing natural selection to take place?"
We may have taken evolution in our own hands since our drugs and foods can change our genes.
"It's cruel but have humans allowed those with genetic diseases to procreate weakening the genetic pool?"
Maybe. But it cuts both ways. With the advent of genetic engineering, we can also strengthen the genetic pool.
"Left alone could other species become cognitive?"
Not all. Dinosaurs have 150 million years to get smart but didn't. Pre-human homonids became internet-surfing geeks in just four million years.
The test would be to NOT program the robot to do anything in particular, THEN paint it's face. If the robot uses the mirror to check out the new paint job, then you know!
Reply | Report Abuse | Link to this"Dinosaurs have 150 million years to get smart but didn't."
Reply | Report Abuse | Link to thisWe have no way of knowing just how intelligent that the dinosaurs commonly known, in general, as raptors might have been, but there are some indications that some of them may have hunted in groups, employing cooperative strategies. They along with other dinosaurs certainly did evolve, adapting in response to changing conditions. Please see: http://en.wikipedia.org/wiki/Dromaeosauridae
We certainly have no way of knowing how intelligent they might have become if they had not been annihilated. It's not too great a leap to argue that raptors, had they survived the past 65 million years, might have developed large brains rather then the hominids that preceded the development of modern humans.
"Pre-human homonids became internet-surfing geeks in just four million years."
Hominids did develop into modern humans (as well as modern apes), but I don't think that any subsequent evolutionary biological changes in modern humans can account for the development of atomic bombs, television or the wondrous internet.
Take away the infrastructure provided by the modern industrial, technological society and few modern humans could survive using their own wits. We have not evolved so far from early modern humans - without our accumulated societal knowledge there's little evidence that we are in any way superior.
To my knowledge there are two types of organism. Fist are those that are evolving and second are those that are extinct. As long as the environment is changing, species change too.
Reply | Report Abuse | Link to this@Nagnostic
Reply | Report Abuse | Link to thisI agree with your first comment, well done, I gave up.
"I tend to believe that all organisms are self-aware"
Me too. Occam's razor. Anytime I see something that contains the idea that self-awareness is restrained to a few animals the argument is always broken some way or another by various semantic sloppinesses.
Three examples of animal behavior, I have witnessed, are any of them signs of self awareness?
Reply | Report Abuse | Link to thisA gorilla in a zoo, behind bars. A man was deliberately teasing him, after a while, the gorilla shit in his hand and threw it in the face of the idiot.
A old dog in the garden snoozing in the sun, a cat walks by just in front of the dog, I see the dog looking at the cat, but snoozes on. I laugh out loud, the dog sees me, immediately he jumps up and runs after the cat, wildly barking.
My cat loved the smell of my sweat, once after I had been gardening in the sun, I left my shirt on the garden table, where I was sitting with my wife. The cat jumps up on the table, rolls around with the shirt and falls on the ground. I laugh (I do that a lot), my wife says poor kitty and tries to comfort her, the cat scratches her for the first and only time.
I am well aware, that these incidents are not scientific double blind tests, but to me all are examples of animals reacting to some kind of slight by humans, that possibly hurt their feelings? :-;
I remember when doctors agreed that babies were not smiling, it was gas. Somehow, when enough women became doctors, they suddenly realised that babies do smile!
"We have no way of knowing just how intelligent that the dinosaurs commonly known"
Reply | Report Abuse | Link to thisWe are sure they were not as smart as humans. I subscribe to SETI's definition of intelligent life: if you can build a radio transmitter, you're in. That may be too harsh as Shakespeare would not qualify as intelligent life.
"I don't think that any subsequent evolutionary biological changes in modern humans can account for the development of atomic bombs, television or the wondrous internet."
The biological change in homo sapiens compared to homonids is your three-pound brain that consumes 25 watts of power. A quarter of your calorie intake is consumed by your brain. No other animal has such big brain and enormous brain power relative to its body size.
And the effect of big brain is dramatic. If you have a two-pound brain, you walk upright and use stone tool. If you have a three-pound brain, you walk on the moon and invent the world wide web.
"It's not too great a leap to argue that raptors, had they survived the past 65 million years, might have developed large brains"
Reply | Report Abuse | Link to thisDinosaurs had 150 million years to get smart but didn't. Why would another 65 million years make them as smart as humans? They had such huge bodies if they evolved the same brain-to-body size ratio as humans, they would break their neck when they turn their head.
If dinosaur brain consumed as much energy as human brain relative to our body size, they would be eating all day just to keep up with the energy demand. They would have no time to think and develop civilization.
So nice to see comments that question the significance and validity of the article. Especially if one considers that the brain is simply a device that consciousness ("mind") uses to interact with the physical world. Thus knowledge about each species is limited to observations about their outward interactions and leaves untouched the intrinsic experience which may be much more vast than the average myopic human might imagine.
Reply | Report Abuse | Link to this"the brain is simply a device that consciousness ("mind") uses to interact with the physical world."
Reply | Report Abuse | Link to thisYou mean you can think without your brain? Or you believe in ghosts and spirits? You can fantasize about the paranormal but if you have evidence for it, you can collect a million bucks from James Randi.
Correction
Reply | Report Abuse | Link to thisReplace "various semantic sloppinesses" with "excessive semantic sloppinesses"
Dr. Duncan,
Reply | Report Abuse | Link to thisRe: "Identifying the precise structural differences that make some creatures self-aware and others not is quite challenging. Most important, it is difficult to pinpoint and compare subtle structural differences across species in the face of more dramatic differences in brain morphology."
What is the evolutionary explanation for that admission?
Last correction
Reply | Report Abuse | Link to this"excessive semantic sloppinesses"
I'm not happy with the word sloppy, too much negative connotations, and context is missing. What may be ok in poetry or art in general may not be appropriate in more semantically rigorous fields like the sciences.
In addition, the asertion of self-awareness is vulnerable to conflation with our verbal method of socialization. Self-awareness would seem to be innate in any species in which a 3rd order theory of mind can be shown, whether their communication has a complex verbal component or not.
Reply | Report Abuse | Link to thisSocial learning is vital to many mammals. Imitation is a basis for creativity, and indeed, can be regarded as creative, and this would seem to have roots in memory, as well as perhaps needing some self-awareness for such behavior to function efficiently. Creative response - additive behaviors upon those learned, occur repeatedly in many species.
Many species use varied signals and communications; we might expect receivers of communications and other intentional behaviors to have response through amygdala/hippocampal areas. Since our own cognitions and memories are mediated (in the sense of metacognizing their relative seriousness or other validity - awareness & response to emotional response) through these structures, I suggest that a search for self-awareness begin following limbic system processes, rather than portions of the human brain that are not well- or completely developed until members of that species are near 20 years old or longer.
Some areas of our brain are involved with strategizing and emotion (cingulate gyrus), and several other species not closely related for over 60 million years show these areas extremely well-developed.
We should not conflate self-awareness with primate ability to grasp/finger dexterity, and a specific kind of intelligence related to body structure. To arrogate self-awareness only to species which physically manipulate may be serious error.
We see other species attentive to mirrors for an extremely short period, before ignoring those tools. Self-awareness may be so innate that some species quickly recognize reflections of their own selves as innocuous. "What's so important about a spot that doesn't itch?" might be a cognition useful to species whose senses may be (like neurons themselves) only harbingers, until corroborated by other senses. Then, when broad sensory evidence accumulates, it is time for a self-aware being (to be aware of hunger or danger certainly seem to be important self-aware responses) to act.
To think verbally is different than to be self-aware. It is neither necessary nor sufficient.
Self-awareness most likely concerns a spectrum of behaviors, not all of which are social.
I agree with Professor Duncan that neural interconnections are extremely important in self-awareness.
Regarding raptor dinosaur intelligence: they could have been comparably intelligent to hominids, and capable of evolving large brains just as the hominids' progenitors did. Why did't chimpanzees develop large brains? Perhaps some specific raptor would have adapted to changing conditions similarly to modern humans.
Reply | Report Abuse | Link to thisTo clarify: "I don't think that any [recent] evolutionary biological changes in modern humans can account for the [recent] development of atomic bombs, television or the wondrous internet."
Recent technological developments that have occurred at an ever increasing rate during the past perhaps few thousand years were not the results of any brain developments produced by biological evolution but the development of societal transmission and accumulation of
information through human generations.
Re. "Dinosaurs had 150 million years to get smart but didn't. Why would another 65 million years make them as smart as humans? They had such huge bodies if they evolved the same brain-to-body size ratio as humans, they would break their neck when they turn their head."
The raptors weren't around 150 million years - they were rapidly evolving and diversifying, adapting to many different environments before their catastrophic demise. Not all dinosaurs were sauropods - were they?
You can speculate all you want but the fact remains raptors didn't get smart in 150 million years and homonids got smart in 4 million years. That dinosaurs won't get smart given another 65 million years is not just my opinion, it is the opinion of paleontologists studying dinosaurs.
Reply | Report Abuse | Link to thisTechnological developments are the product of human's large brain. It's silly to argue it's technology not the large brain. If that is so, all animals with small brains would be surfing the internet.
You only have to watch "Jurassic Park" to know that raptors had been around since the Late Jurassic period 150 million years ago.
Raptors "only" had 85 million years to get smart. That's still long compared to 4 million years. And their evolutionary descendants the birds didn't get smart either despite another 65 million years. Look at the birds. They're still bird brain.
Reply | Report Abuse | Link to this