Perceptual psychology and the brain sciences emphasize the communality in the way that people experience reality. Leaving aside cases of brain damage or mental disease, we all see the sun rise in the east, enjoy the scent of a rose and experience a jolt of fear when we are woken up in the middle of the night by the sound of breaking glass. This is a reflection of the great similarities of our brains compared with the brains of our close cousins on the evolutionary tree, the great apes. Laboratory science reinforces this bias by lumping together the performance of its subjects on any one experiment and reporting only the average and the variation around this mean. This conflation is also true for the telltale hot spots that show up in functional magnetic resonance brain images that we are used to seeing in newspapers, in magazines such as this one, on television and in the movies.
Yet as we know from our own life, each one of us has his or her own preferences, likes and dislikes. Some people are acutely sensitive to flashing lights, some have perfect pitch, some cannot see in depth, some can introspect and analyze their own failures and triumphs, whereas others—remarkably frequently, public figures such as politicians—lack this knack. Take me. I am hopelessly attracted to brilliant colors. As a magpie is drawn to anything glittering, I am drawn to school-bus yellow, tangerine orange, burgundy red, rich magenta, electric violet, imperial purple and navy blue. My love of the garish is reflected in my flowery shirts and pants and, I’m sure, in an enhanced cortical representation of these hues.
It is obvious that if the apparatus that senses the world differs between two individuals, then the conscious experience of the brains wired to these sensors cannot be the same either. In a previous Consciousness Redux column, I discussed color blindness—the fact that about 7 percent of men lack one of the genes for the retinal photopigments needed to see hue. But what about differences in the brain proper? Do they influence consciousness in measurable ways? To answer this question, scientists must plumb the minds of many individuals and relate them to measures of their brains. The widespread availability of fMRI scanners makes such a project feasible today.
Cognitive neuroscientist Geraint Rees, a professor at the Wellcome Trust Center for Neuroimaging at University College London—undoubtedly the world’s leading fMRI center—published a trio of studies that relates differences in the way people experience things with differences in gross aspects of their cerebral neocortex, the highly convoluted part of the forebrain that crowns the brains of all mammals.
In one study 30 subjects looked at the Ponzo illusion while their brains were scanned. Whereas everybody who looks at the Ponzo perceives the upper bar as larger than the lower one, the magnitude of this effect differs substantially across individuals. (The size of the illusion is established by asking how much larger the lower bar has to be to make it look the same size as the upper one.) Surprisingly, these differences are reflected in the surface area of the primary visual cortex (V1) at the back of the head. For unknown reasons, the area of V1 can differ by a factor of three among people (unfolded, the size and width of a typical V1 compares with that of a credit card). Rees and his collaborators discovered that the smaller a person’s V1, the more powerfully he or she experiences the illusion. Those individuals with a large V1 judged the size of the bars to be more similar than those with a smaller V1. Curiously, the size of the two immediately adjacent visual areas did not influence the amplitude of the illusion.
Clues from Illusions
Bistable illusions are those delightful images that can be seen in one of two ways. Probably the best known is the Necker cube, or the “old woman, young girl illusion.” These two interpretations flip back and forth. The time it takes for the percept to flip differs consistently across individuals. One person might see the figure alternate every five seconds; another sees it flip every 10.
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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.