>
NewScientist.com news service
> Graham Lawton
>
>
http://www.newscientist.com/channel/being-human/mg19526221.300-mind-t...
>
> 1 Seeing isn't believing
> TAKE a moment to observe the world around you. Scan the horizon with your eyes.
> Tilt your head back and listen. You're probably getting the impression that your
> senses are doing a fine job of capturing everything that is going on. Yet that
> is all it is: an impression.
>
> Despite the fact that your visual system seems to provide you with a continuous
> widescreen movie, most of the time it is only gathering information from a tiny
> patch of the visual field. The rest of the time it isn't even doing that.
> Somehow from this sporadic input it conjures up a seamless visual experience.
>
> What is going on? Bang in the middle of your retina is a small patch of densely
> crowded photoreceptors called the fovea. This is the retina's sweet spot, the
> only part of the eye capable of seeing with the rich detail and full colour we
> take for granted. This tiny spot - which covers an area of our visual field no
> bigger than the moon in the sky - feeds your visual system almost all of its raw
> information.
>
> To build up a big picture, your eyes constantly dart about, fixating for a
> fraction of a second and then moving on. These jerky movements between fixations
> are called saccades, and we make about three per second, each lasting between 20
> and 200 microseconds.
>
> The curious thing about saccades is that while they are happening we are
> effectively blind. The brain doesn't bother to process information picked up
> during a saccade because the eyes move too rapidly to capture anything useful.
> All in all, your visual system works like a man blundering around in the dark
> waving around a flickering torch with a very narrow beam.
>
> Despite the fact that you don't normally notice saccades, you can catch them in
> action. Look at your eyes close-up in the mirror and flick your focus back and
> forth from one pupil to another. However hard you try you cannot see your eyes
> move - even though somebody watching you can. That's because the motion is a
> saccade, and your brain isn't paying attention. Now pick two spots in the
> corners of your visual field and flick your gaze from one to the other and back
> again. If you're lucky you'll notice, just barely, a brief flash of darkness.
> This is your visual cortex clocking off.
>
> So how does your brain weave such fragmentary information into a seamless movie?
> This remains something of a mystery. The best explanation, according to Andrew
> Hollingworth of the University of Iowa in Iowa City, is that your short-term and
> long-term visual memories retain information from previous fixations and
> integrate them into a here-and-now visual experience (Visual Cognition, vol 14,
> p 781).
>
> There is also some guesswork going on. You can get a feel for this from the
> frozen-time illusion - the sensation that you sometimes get when you look at a
> clock and the second hand appears to freeze momentarily before tick-tocking back
> into action.
>
> This happens because of saccades. To compensate for the temporary shut-down of
> vision, your brain makes a guess at what it would have seen, but it does so
> retrospectively. So the 100 or so milliseconds of blindness gets back-filled
> with the image that appears after the saccade is over. If your eyes happen to
> alight on the clock just after the second hand has moved, your brain assumes
> that the hand was in that location for the duration of the saccade too. The
> "second" then lasts about 10 per cent longer than normal, which is enough for
> you to notice.
>
> The weirdness isn't confined to vision. Your auditory system is also full of
> gaps and glitches that the brain cleans up so we can make sense of the world.
> This is especially true of speech.
>
> In everyday life we encounter lots of situations that obscure or distort
> people's voices, yet most of the time we understand effortlessly. This is
> because our brain pastes in the missing sounds, a phenomenon called phonemic
> restoration. It is so effective that it is sometimes hard to tell that the
> missing sounds are not there.
>
> A good demonstration of this effect was published last year by Makio Kashino of
> NTT Communication Science Laboratories in Atsugi, Japan. He recorded a voice
> saying "Do you understand what I'm trying to say?" then removed short chunks and
> replaced them with silence. This made the sentence virtually unintelligible. But
> when he filled the gaps with loud white noise, the sentence miraculously becomes
> understandable (Acoustic Science and Technology, vol 27, p 318).
>
> "The sounds we hear are not copies of physical sounds," Kashino says. "The brain
> fills in the gaps, based on the information in the remaining speech signal." The
> effect is so powerful that you can even record a sentence, chop it into
> 50-millisecond slices, reverse every single slice and play it back - and it is
> perfectly intelligible. You can listen to Kashino's sound files
athttp://asj.gr.jp/2006/data/kashi/index.html.
>
> "The sounds we hear are not copies of physical sounds"Another demonstration of
> the brain's ability to extract meaning from distorted signals is a form of
> synthesised speech called sine-wave speech. When you first hear a sentence in
> sine-wave speech it sounds alien and unintelligible, somewhat reminiscent of
> whistling or birdsong. But if you listen to the same sentence in normal speech
> and then return to the sine-wave version, it suddenly snaps into auditory focus.
> Try as you might, you cannot "unhear" the words that you didn't even realise
> were words the first time you heard them (listen to demos
atwww.mrc-cbu.cam.ac.uk/~mattd/sine-wave-speechandwww.lifesci.sussex.ac.uk/home/...).
>
> According to Matt Davis of the UK Medical Research Council's Cognition and Brain
> Sciences Unit in Cambridge, this happens because the brain has circuits that
> respond to speech, but doesn't switch them on unless it detects spoken language
> (Hearing Research, vol 229, p 132). Sine-wave speech isn't speech-like enough to
> trigger the circuits, but once you know it is speech they spring into action.
> "It's an example of top-down influence," says Davis. "What you know about what
> you're hearing changes the way you hear it."
>
> Given the tricks that your visual and auditory systems play, it probably comes
> as no surprise that when they get together, fights can break out. A good
> demonstration of this is the McGurk effect, in which listening to a series of
> identical syllables such as "ba ba ba ba" while watching somebody mouth "ba da
> la va" makes you hear "ba da la va". Try it for yourself
atwww.faculty.ucr.edu/~rosenblu/lab-index.html.
>
> Until recently, psychologists believed that the visual system always trumps the
> other senses, but in 2000 a team of psychologists at the California Institute of
> Technology in Pasadena proved that this isn't the case. They showed volunteers a
> single flash on a computer screen. If they accompanied the flash with two very
> short beeps, the volunteers saw two flashes - in other words, this time the
> auditory system wins (Nature, vol 408, p 788). See the illusion
atwww.cns.atr.jp/~kmtn/soundInducedIllusoryFlash2/index.html.
>
> 2 This is not my nose
> YOU may know the crossed-hands illusion. Hold your arms out in front of you and
> cross them over, rotate your hands so your palms face each other, then mesh your
> fingers together. Now slowly rotate your hands up between your arms so you're
> staring at your knuckles. Ask someone to point to one of your index fingers,
> then attempt to move it. Did you move the wrong one?
>
> If so, you've just experienced a minor failure of your body schema - your mental
> representation of the location, position and boundaries of your body. Your brain
> builds this up by drawing on data from vision, touch and a body-wide network of
> proprioceptive sensors that monitor position. Your body schema is a critical
> part of self-awareness, which is why it feels so odd when it goes wrong.
>
> In the crossed-hands illusion, the schema fails because of a confusing visual
> input. You don't normally see your hands in this convoluted position; the finger
> you move is the one that is pointing in the direction that the correct one would
> be pointing if you had simply clasped your hands as if in prayer.
>
> An even odder way of disturbing your body schema is an illusion that taps
> straight into your sense of body ownership. Known as the rubber-hand illusion,
> it fools you into thinking a rubber hand - or even a piece of wood, or a table -
> is part of your body.
>
> To experience the illusion, get hold of a model hand (it doesn't have to be very
> realistic) and put it on the table in front of you. If it is a left hand, put
> your actual left hand somewhere you can't see it, in the same pose as the rubber
> hand. Now get someone to touch and stroke your unseen hand and the rubber hand
> with identical movements. If you concentrate on the rubber hand, you will
> probably get the uncanny feeling that it is your own. (See a video of the rubber
> hand illusion here)
>
> What this illusion shows is that your sense of body ownership is less anchored
> in reality than you think. Your brain will happily override information from
> proprioception to conjure up an incorrect yet coherent body schema based on
> vision and touch.
>
> In fact, your mental body map is an absolute sucker for visual information. This
> year Frank Durgin of Swarthmore College in Pennsylvania set up the illusion as
> described above but instead of touching the rubber hand he merely "stroked" it
> with light from a laser pointer, leaving the unseen hand alone. Two-thirds of
> 220 subjects reported a sense of ownership of the rubber hand and said they had
> the sensation of heat and even touch from the laser pointer (Psychological
> Science, vol 18, p 152). "It's obvious the hand is rubber - no one is fooled at
> all," says Durgin. "But if your brain decides it's your hand, all the conscious
> awareness in the world won't change it."
>
> If you can't get hold of a fake hand, there are other (though less reliable)
> ways to experience the illusion. Some people can be fooled into believing a
> piece of wood has replaced their hand. Around half of people can even be made to
> feel a table top is part of their body. Sit at a table and put your hand out of
> sight underneath. Get someone to tap and stroke this hand while doing exactly
> the same to the table top directly above. If you watch the table top, you may
> experience the illusion that the table has become part of your body.
>
> Proprioception may be the junior partner to vision and touch in creating your
> body schema, but it still plays a key role. You can demonstrate this with an
> illusion that taps into proprioception alone. This Pinocchio illusion is hard to
> do without a specialist piece of equipment called a physiotherapy vibrator, but
> if you can get hold of one, try this. Close your eyes, touch the tip of your
> nose and then get somebody to apply the vibrator at about 100 hertz to skin at
> the very top of your bicep. This creates the strong sensation that you are
> straightening your elbow, and that your nose is simultaneously growing longer
> and longer, like Pinocchio's.
>
> Vibrating the skin above a tendon excites stretch receptors in the muscle,
> creating a powerful sensation that the muscle is stretching and the joint is
> extending. This confuses your proprioceptors, which revise your body schema
> accordingly. The result is rather like having a phantom limb: the sensed
> position of your arm in space doesn't correspond to its actual position.
>
> If you're touching your nose at the same time, this leads to a weird sensation
> that it is growing. Your brain integrates the touch sensation from your fingers
> with the "movement" of your arm and comes to the erroneous conclusion that your
> nose must be growing to fill the gap.
>
> The Pinocchio illusion is an important tool for understanding how the brain
> calculates the size and shape of our bodies. This isn't just an academic
> question. When it goes wrong, such as in body dysmorphic disorder, anorexia and
> phantom limb, the results can be devastating (PLoS Biology, vol 3, p e412).
>
> 3 A brain of two halves
> WOULD you consider yourself to be logical and analytical or creative and
> empathic? According to popular psychology you're one or the other, and it's all
> down to which half of your brain you use the most: the rational and calculating
> left or the intuitive, artistic right.
>
> It's a myth, of course, but like all good ones it contains a grain of truth.
> Your cerebral cortex - the outer layer of your brain that deals with higher
> functions - is indeed split into two halves. They are connected by a flat bundle
> of nerve fibres called the corpus callosum, but work in subtly different ways -
> and these differences occasionally flicker into your conscious awareness.
>
> The left-brain/right-brain myth arose from experiments done in the early 1970s
> on people who had had their corpus callosum cut as a last-ditch treatment for
> epilepsy. These "split-brain" patients showed some strikingly odd responses to
> information that was preferentially sent to one side of the brain or the other
> by presenting it to the extreme left or right of their visual field. This works
> because the right visual field is monitored by the right eye, which routes
> straight into the left brain, and vice versa.
>
> For example, when a word or picture is presented to their right brain,
> split-brain patients are often unable to read or recognise it. This and similar
> experiments led to the idea that the left side of the brain deals with logic and
> facts while the right side is more intuitive and interpretive. We now know that
> this dichotomy is too simplistic, but its essence holds true. The latest view is
> that the two hemispheres have subtly different styles of information processing:
> the left has a bias towards detail, the right a more holistic outlook. You can
> watch a video of a split-brain experiment
atwww.youtube.com/watch?v=ZMLzP1VCANo&mode=related&search=.
>
> "Split-brain patients often can't read words sent to the brain's right side"Most
> people, of course, have a functional corpus callosum that shunts information
> between the hemispheres. Even so, subtle left-right differences exist. One task
> where the hemispheres operate differently is face recognition. When most of us
> see a face, our right cerebral hemisphere does the lion's share of the work
> recognising its gender and decoding its expression. And because the right
> hemisphere is fed by the left visual field, that means we have a notable
> left-sided bias in our judgement of faces.
>
> Look at this pair of faces (left). Which appears happier? Chances are you chose
> the bottom one. The two faces are, however, identical apart from being mirror
> images of one another. The picture is called a chimeric face and is made by
> taking two pictures of the same face, one with a neutral expression and the
> other smiling, chopping the pictures in half and joining the two mismatched
> pieces. Our general bias towards the left side of the face (as we look at it)
> makes us see the faces as different even though they are essentially equivalent.
>
> It isn't just visual processing that is lateralised. There is some evidence that
> emotion is too, with the right side of the brain more specialised for negative
> emotions and the left for positive ones. Amazingly, simply activating one or
> other hemisphere by moving parts of your body can noticeably change your
> emotional state.
>
> You can experience this by repeating an experiment first done in 1989 by Bernard
> Schiff and Mary Lamon of the University of Toronto in Canada (Neuropsychologia,
> vol 27, p 923). They asked 12 volunteers to perform a "half smile", lifting one
> corner of their mouths and holding it for a minute. Left-smilers reported
> feeling sadder afterwards, while right-smilers felt more positive.
>
> Other researchers have reproduced the effect simply by getting people to
> contract the muscles of their left or right hand a few times. More recent
> research has suggested that motivation is similarly affected: people who
> performed right-sided muscle contractions became more assertive and spent longer
> trying to crack an impossible maths puzzle.
>
> Unsurprisingly, these claims are controversial, with some teams failing to
> replicate the results. Last year, however, Eddie Harmon-Jones of Texas A&M
> University in College Station used EEG to confirm that flexing the hand muscles
> produces changes in emotion, but only when it is preceded by activation of the
> opposite cortex (Psychophysiology, vol 43, p 598). The left-brain/right-brain
> legend, it appears, is alive and well.
>
> 4 Probe your subconscious
> IT WAS a ground-breaking investigation into the nature of consciousness and free
> will. In 1983, psychologist Benjamin Libet of the University of California, San
> Francisco, hooked five volunteers up to an EEG machine and asked them to make
> voluntary movements, such as lifting a finger, whenever they felt like it.
> Watching the electrical activity in their brains, he discovered that his
> subjects only became consciously aware of their intention to act a few hundred
> milliseconds after their brain had initiated the movement. Libet was forced to
> conclude that what feels like a conscious decision may in fact be nothing of the
> sort (Brain, vol 106, p 623).
>
> This experiment was the first demonstration of what is now an established theory
> in neuroscience: a major proportion of your thoughts and actions - even things
> you believe you are in conscious control of - actually take place in your
> unconscious. Most of the time you are essentially flying on autopilot.
>
> Libet's experiment involved equipment that you're unlikely to have at home, but
> you can tap into a similar phenomenon using what is known as the "ideomotor
> effect". Make a pendulum out of a paper clip and a piece of thread and dangle it
> over a cross drawn on a piece of paper. Ask yourself a simple yes/no question,
> such as "am I at home?" or "do I have a cat?", and tell yourself that if the
> pendulum swings clockwise, the answer is yes, while anticlockwise means no.
> Spookily, the pendulum will generally start rotating in the direction of the
> correct answer.
>
> It looks supernatural, but it's not. The reason it works is that, as soon as you
> ask the question, your unconscious brain fires up motor preparation circuits in
> anticipation of the answer it expects to see. These circuits initiate subtle
> muscle movements that you are not normally aware of - except when they are
> amplified by a pendulum (or dowsing stick or Ouija board). This is your
> unconscious brain in action.
>
> A different aspect of your mental underworld is reflected in your "implicit
> assumptions". Your subconscious mind isn't just planning and executing actions,
> it also spends a great deal of time analysing the world, looking for patterns
> and relationships that can help you navigate through life. The conclusions it
> comes to are called implicit assumptions - subtle prejudices about people and
> events. For example, if you hear on the radio that a teenage boy has been shot
> dead in a car park near his home, it's almost impossible not to make assumptions
> about his family background and the area where he lived.
>
> "Everybody has implicit assumptions," says Brian Nosek, a psychologist at the
> University of Virginia in Charlottesville who played a big part in their
> discovery. "They're a necessary part of how the brain operates and they
> generally serve us very well."
>
> But not always. Nosek and colleagues argue that because we are not in control of
> our implicit assumptions, and are seldom aware of them, it is possible to
> develop unconscious prejudices that your conscious mind would find unappealing
> or even abhorrent - such as associating men with science and women with the
> arts, preferring thin people to fat people or assuming that blonde women are
> stupid. "You may think you're egalitarian, yet your associations are often quite
> different," says Nosek.
>
> Nosek and colleagues have devised a way to access these implicit assumptions
> (take the test
athttps://implicit.harvard.edu/implicit). The tests are based on
> the idea that people find it easier to recognise pairs of stimuli that fit their
> unconscious assumptions - white people and positive words or black people and
> negative words, for example. People often find the results of their tests
> "provocative", says Nosek. "The most common implicit associations are race and
> age - they're quite profound."
>
> Maybe sometimes it is better to ignore your unconscious mind.
>
> 5 Pay attention!
> IMAGINE you are walking down the street and a passer-by asks you for directions.
> As you talk to him, two workmen rudely barge between you carrying a door. Then
> something weird happens: in the brief moment that the passer-by is behind the
> door, he switches places with one of the workmen. You are left giving directions
> to a different person who is taller, wearing different clothes and has a
> different voice. Do you think you would notice?
>
> Of course you would, right? Wrong. When researchers at Harvard University played
> this trick on 15 unsuspecting people, eight of them failed to spot the change.
>
> What this demonstrates is a phenomenon called "change blindness". It happens
> because of a chronic shortage of a crucial mental resource: attention. You are
> blithely unaware of most of what is going on around you, to the point where you
> can fail to notice "obvious" changes in your surroundings.
>
> Attention is not well understood, but whatever it is, we have a limited amount.
> Of all the information entering or being generated by your brain at any one time
> - sights, sounds, memories, ideas and so on - only a tiny fraction enters your
> consciousness. Object-tracking studies suggest that the maximum number of items
> we can attend to at any one time is around five or six (see demos
athttp://ruccs.rutgers.edu/finstlab/demos.htm).
>
> Scientists studying attention spend a lot of time playing with change blindness
> because it provides direct access to the attentional system. In the door
> experiment, the subjects fail to see the change because their attention is
> elsewhere and the door conceals what would otherwise be attention-grabbing
> motion.
>
> You can experience the same thing by watching "flicker images". These consist of
> two consecutive images that differ only in one key feature - two cowboys who
> swap heads, say. If the images are flashed up in quick succession with a brief
> blank screen between them (which acts like the door), most people take an
> astonishingly long time to spot the difference (see demos
atwww.psych.ubc.ca/~rensink/flicker/download, or try flicking your attention
> between the two images in the diagram below).
>
> Similarly, we often fail to notice blatant continuity errors when films cut from
> one scene to another. We also usually fail to detect gradual changes to a static
> scene, such as the addition of a large building (see demos
athttp://viscog.beckman.uiuc.edu/djs_lab/demos.htmlandhttp://nivea.psycho.univ-paris5...).
>
> "Basically, the explanation is that attention is needed to see change," says
> psychologist Ronald Rensink of the University of British Columbia in Vancouver,
> Canada. "Attention is drawn automatically to the motion signals that accompany a
> change. But if these are swamped, then the observer can't rely on automatic
> control, but needs to hunt around with their attention."
>
> A similar phenomenon is motion-induced blindness, in which concentrating on a
> moving pattern causes what should be very prominent static objects - such as
> bright yellow dots - to disappear (see demos
athttp://pantheon.yale.edu/%%7Ebs265/demos/MIB-percScotoma.html). Motion-induced
> blindness was only discovered in 2001 and it is still unclear why it happens,
> but most researchers think it has something to do with attentional resources.
>
> There is a related and even more counter-intuitive demonstration of our limited
> capacity for attention. If you are deliberately concentrating on something, it
> can render you oblivious to other events that you would normally have no trouble
> noticing. This "inattention blindness" is probably the reason why motorists
> sometimes collide with objects such as pedestrians and buses that they simply
> "didn't see".
>
> The most famous demonstration of inattention blindness was staged in 1999 by
> Daniel Simons and Christopher Chabris of the University of Illinois at
> Urbana-Champaign. It involves a game of basketball. Chances are you've seen it
> or read about it before. If not, have a look
athttp://viscog.beckman.uiuc.edu/grafs/demos/15.html. The task is to count the
> number of passes made by the team in white. You won't believe your brain.
>
> 6 Made-up m emories
> A FEW years ago, the actor Alan Alda visited a group of memory researchers at
> the University of California, Irvine, for a TV show he was making. During a
> picnic lunch, one of the scientists offered Alda a hard-boiled egg. He turned it
> down, explaining that as a child he had made himself sick eating too many eggs.
>
> In fact, this had never happened, yet Alda believed it was real. How so? The egg
> incident was a false memory planted by one of UC Irvine's researchers, Elizabeth
> Loftus.
>
> Before the visit, Loftus had sent Alda a questionnaire about his food
> preferences and personality. She later told him that a computer analysis of his
> answers had revealed some facts about his childhood, including that he once made
> himself sick eating too many eggs. There was no such analysis but it was enough
> to convince Alda.
>
> Your memory may feel like a reliable record of the past, but it is not. Loftus
> has spent the past 30 years studying the ease with which we can form "memories"
> of nonexistent events. She has convinced countless people that they have seen or
> done things when they haven't - even quite extreme events such as being attacked
> by animals or almost drowning. Her work has revealed much about how our brains
> form and retain memories.
>
> While we wouldn't want to plant a memory of a nonexistent childhood trauma in
> your own brain, there is a less dramatic demonstration of how easy it is to form
> a false memory called the Deese-Roediger-McDermott paradigm. Read the first two
> lists of words and pause for a few minutes. Then read list 3 and put a tick
> against the words that were in the first two. Now go back and check your
> answers...
>
> "List 1
>
> apple, vegetable, orange, kiwi, citrus, ripe, pear, banana, berry, cherry,
> basket, juice, salad, bowl, cocktail""List 2
>
> web, insect, bug, fright, fly, arachnid, crawl, tarantula, poison, bite, creepy,
> animal, ugly, feelers, small
>
> (Now wait a few minutes)""List 3
>
> happy, woman, winter, circus, spider, feather, citrus, ugly, robber, piano,
> goat, ground, cherry, bitter, insect, fruit, suburb, kiwi, quick, mouse, pile,
> fish"From issue 2622 of New Scientist magazine, 19 September 2007, page 34-41
