Rees and his group used a dynamic version of such bistable illusions: a cloud of moving dots perceived as a cylinder rotating either to the left or to the right. Here the scientists correlated the width of the cortical sheet—the thickness of its gray matter—with how long each stable percept lasts before it switches. Scanning the brains of 52 subjects—in a field dominated by studies that come to grand conclusions by querying a handful of brains—they found only a single region, the left and right superior parietal lobe (SPL), in which the thickness of the gray matter (and its density) significantly and consistently correlated negatively with the perceptual duration. In other words, the thicker the SPL cortex, the faster two interpretations switch back and forth. It is known from other imaging and clinical studies that the SPL in the back of the brain controls selective visual attention, but how the thickness and density of SPL gray matter should be important is anybody’s guess.
Ask people what they believe to be the defining feature of consciousness, and most will point to self-awareness. To be capable of being aware of your hopes, to worry about your spouse’s illness, to wonder why you feel despondent or why he provoked you is taken to be the pinnacle of sentience. Self-awareness is, by and large, absent in nonprimates. Although my dog—as with many and, perhaps, all animals—experiences the sights, sounds and, in particular, the smells of life, she doesn’t worry why her tail isn’t wagging as it used to or whether tomorrow’s food will appear.
So can differences in this elusive higher-order aspect of consciousness be tied to differences in brain structures? Yes, as a just published third study by Rees and his colleagues concludes.
Thirty-two healthy volunteers carried out a difficult visual task in the scanner. They had to judge which one of a number of faint patches was a tad more salient than the other ones; this judgment was purposefully made demanding. Following each trial, subjects had to choose a number between one and six, indicating the confidence they had in their own judgment. A six indicated that they were very confident of their judgment, whereas a one implied a guess. That is, they were asked to introspect: Are you sure you just saw the bright patch here? Psychologists know this as meta-cognition: thinking about thinking.
Not surprisingly, subjects differed greatly in the accuracy of their judgments (independent of the level of their performance). Think of the game show Who Wants to Be a Millionaire, where contestants have to judge whether they want to use a lifeline before they know the answer, depending on their confidence. Some people are astute, using the lifelines wisely; other people fritter them away. The cognitive scientists extracted a measure of variability of introspection and discovered that this measure correlated with variability in gray matter volume in the right anterior prefrontal cortex. The more neurons you have in this region in the front of the brain, the better your introspection. Not that your performance goes up, but the insight you have into your performance—whether you thought you did well or not—increased. Patients with lesions in these regions typically lose the ability to introspect. And this part of the neocortex has expanded more than any other region in primates. Again, the neuronal mechanisms underlying this correlation remain unknown for now.
Rees’s studies establish that differences in the morphology, or shape, of our brains are mirrored in differences in the way we consciously experience and apprehend the world, including our own brains and bodies. In this way, neuroscience maps the physical structure of the material brain onto the inner geometry of phenomenal and ineffable experience.
This article was originally published with the title Think Different.
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7 Comments
Add CommentI find it very strange and somewhat irresponsible for a writer of a presumably scientific blog to present experimental attempts at deriving the commonalities among human perception as some sort of a "bias". Those are important scientific questions with wide ranging implications. I am also absolutely perplexed by you saying that presenting the variance around the mean - the measure of differences in the sample! - is somehow reinforcing the idea that everybody is the same.
Reply | Report Abuse | Link to thisThat cavalier introduction seriously took away from the article, in my opinion, - and it was not really necessary to make such colorful assertions.
I think if you were to edit all that first paragraph down to a simple phrase like "While typically researchers have concentrated on the commonalities,.." - and then talk about differences. This way you are writing about what's interesting to you, what's actually promised in the title of the article, and not making rash statements that make people cringe.
Reply | Report Abuse | Link to this"Ask people what they believe to be the defining feature of consciousness, and most will point to self-awareness."
Reply | Report Abuse | Link to thisAssuming you know this is true of "most people," why should self-awareness be considered "the defining" feature of consciousness? Certainly it is a very important feature, but are we not conscious whenever we experience a subjective sensation or thought, with or without concomitant self-awareness?
"Self-awareness is, by and large, absent in nonprimates. Although my dog—as with many and, perhaps, all animals—experiences the sights, sounds and, in particular, the smells of life, she doesn’t worry why her tail isn’t wagging as it used to...."
Assuming you have achieved mind-meld with your dog and you know this to be true, it's not clear some other dog would and could not be aware and have an emotional reaction to a loss of function of an appendage.
Also check out this link: http://www.sciencedaily.com/releases/2008/08/080818220557.htm
for stories about birds, elephants, dolphins showing evidence of self-recognition.
Every man is unique,what may gene he brought, what kind of software developed in his brain all thing are unique so every one behave in his own way, think in his own way Only western civilization donot believed man`s uniqueness.Using statistical survey they erasing man`s uniqueness
Reply | Report Abuse | Link to thisMark, great comment and thanks for the link.
Reply | Report Abuse | Link to thisWe can enjoy the article, reporting to us in a newsy way, findings and skewing bias resulting from averaging. Well-written (thank you, Prof), it must, as commentators noted, gloss over information, and doing so appear biased or inaccurate should one exclusively focus on the content, ignoring the extent of information gathered on neurobiogy and other realms of inquiry.
Reply | Report Abuse | Link to thisI do take issue with the contrast of a domestic dog brain and cognition, as dogs are bred from a species which shows (The wolf now waiting for me, I have biases of my own, resulting through years of observation)significant cognition.
Wild canids show clearly third-order theory of mind, communicate purposely desires, needs, and seek social and physical affective behaviors from others. They have been shown to have an acute sense of fairness, and personal or shared property(!)at various levels, from individual to pair-limited, and pack-limited.
Their cognitions are generally easily recognized as traits evolutionarily useful; we know that traits, cognitions, and behaviors, tend to arise through selection.
Some useful selections arose as long as 65 mya or more, and are shared, as they were useful for the highly variable behavior required for success in an already profoundly evolutionarily sophisticated environment.
And of course, many traits are products of convergence - they arose due to being efficient ways to thrive.
So we must be extraordinarily careful when making assumptions of any inherent different brain activity differing from or mirroring that of another species - or lacking entirely in one or another social mammal.
Every living thing is unique by virtue of its complex gene mix, its uniquely differing environment and experiences, its varying cast of symbiotes.
Mark, it is clear that some species protocols and behaviors (possibly cognitions) are heavily diminished by breeding for specific phenotypic traits. A deep look at traits accomplished, diminished, or seemingly stochastically changed (boy, do I need an editor!), can afford a beginning for inference of what's going on in other minds.
I mean what is bred for is by no means what is achieved, and emotions may well be significant differentials, affecting perceptions.
Humans are a wild species: we have highly variable alleles, phenotypes, behaviors. This variablity is highly useful for generalist species, and this is why the wolf was breedable into such immense variety of dogs.
Strange though, that it all runs opposite to genetic results of niche occupation. Oh, efficiency , oh, economics!
Thanks Mark. As soon as the article hit a part where it was espousing dark age rhetoric, I began to discredit most of its content. The idea that only humans are self aware is an ancient and ignorant excuse for cruelty and brutality and isn't supported by any unbiased research. Indeed it has been proven that some plants are able to recognize individual animals or humans that have caused them harm up to a year previously and will emit an ultrasonic scream when such an individual approaches. These plants have no central nervous system but still differentiate between individuals. If a plant can be that advanced, what then are the real limits of mammals?
Reply | Report Abuse | Link to thisWe have discovered that a wide variety of animals use tools and do actually plan for the future so just where do we embrace science and find a working definition for "self aware"? Self aggrandizing is unscientific despite its frequency among scientists.
If I'm hungry I'm going to chomp on some cooked cow. That does not in any way justify asserting that cows don't feel pain or recognize self or offspring. It is nice to see that some people want actual facts.