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There is a popular psychology myth which states that our brain hemispheres create different personality types: the rational, calculating left makes us logical and analytic, while the intuitive, artistic right brings out our creative and empathic nature. The myth arose in the early 1970s from experiments done on people who had had their corpus callosum cut as a last-ditch treatment for epilepsy (see video below showing what happens to patients as a result of such surgical intervention).

Today scientists have realised that this dichotomy is too simplistic. While the two hemispheres produce differences in information processing, they are much more subtle than previously suggested: the left seems to have a bias towards detail while the right seems to have a more holistic outlook. One example where both hemispheres operate differently is face recognition. For most of us seeing a face, the right hemisphere does the main work, recognising its gender and decoding its expression. And because the right brain is fed information by the left visual field, we have a left-sided bias when judging faces.

The image to the right is called a chimeric face; it is created by taking two pictures of the same face, one with a neutral expression and the other smiling. The pictures are then chopped in half and then rejoined as mismatches. 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; in this particular case it makes most of us interpret the bottom picture as showing a happier expression.

There is some evidence that emotional processing might be lateralised too, with the right hemisphere more specialised for negative emotions and the left for positive ones. Research to support this view needs to be treated with caution though as it might simply resurrect the old myth of right brain / left brain differences. Much of it seems to be based on getting people to move parts of body either on the left or right (e.g. the corner of their mouths or contracting their left or right hands) and then measuring emotional responses.

While claims of resulting happiness or sadness could not always be verified while replicating the tests, EEG has been used last year to show that flexing ones hand produces emotional changes - but only when preceded by activation of the opposite cortex. While the jury therefore is still out on how fundamentally different both hemispheres process information, we can say that differences seem to exist (as the picture to the left and the video below show). That again means that reality is not necessarily what we think it is.

The next post will look at the workings of the unconscious mind; the previous one dealt with the unreliability of our body self image.

[Source: New Scientist]

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I do remember the crossed-hands illusion: holding my arms out in front of me and crossing them over, rotating my hands so my palms face each other, then meshing my fingers together, and slowly rotating my hands up between my arms so I’m looking at my knuckles. Then either asking someone to point to one of my middle or ring fingers or to touch on of them with the tip of my nose and attempt to move it. It is rather hard not to move the wrong one or, in other words, to avoid minor failure of my body schema.

Body schema is the mental memory image of our body, built up from previous impressions of touch, vision and a body-wide network of proprioceptive sensors that monitor positions of the body and its parts. In the crossed-hands illusion the schema fails because the left hand has taken the position of the right hand; therefore when pointing to the left ring finger, the brain creates an impulse to move the right one.

But there is an even more strange schema failure in the rubber-hand illusion which fools people into thinking that a fake hand (or even a piece of wood or a table) is part of their own body (see video below).

What we have here is just another example for how our brain creates reality, even to a point where it totally diverges from what is perceived as reality - by overriding its own proprioception signals. In this particular case of concentrating on the rubber hand, our brain assigns a higher priority to visual input than to touch. This may not be surprising given that visual information seems its preferred mode when creating mental body maps as the following example affirms. In a variation of the rubber-hand illusion Frank Durgin of Swarthmore College left the unseen real hand totally alone, stroking only the rubber hand with a laser pointer. Two thirds of the research participants reported feeling heat sensations and even touch from the laser on the rubber hand, thus integrating it into their own body map. It’s obvious the hand is made of rubber, but this conscious awareness counts for nothing if the brain decides it’s your hand.

Proprioception though is not always the junior partner to vision and touch in creating our body schema; it can play quite a central role as the Pinocchio illusion demonstrates. To experience it, close your eyes and get somebody to apply a so-called physiotherapy vibrator at about 100 hertz to skin at the very top of your bicep while not stretching your arm. The vibration creates the strong sensation that you are straightening your elbow, giving the impression of having a phantom limb: the sensed position of your arm in space doesn’t correspond to its actual position. Touch your nose while applying the vibrator, and you get the feeling that it is simultaneously growing longer and longer, like Pinocchio’s; here the 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. Quite amazing.

All this might sound very academic or just quirky, but this kind of research is quite important. Body schema failures can be quite disorientating and in worse cases debilitating and devastating; a well-know example is anorexia, lesser known ones are dysmorphic disorder and phantom limbs. Understanding how the brain calculates size and shape of our bodies therefore might one day alleviate a lot of suffering.

The next post will look at the curious consequences of the brain being split into two; the previous one dealt with discontinuity of perception.

[Source: New Scientist]

This week’s News Scientist’s cover story looks at the tricks our mind plays to create what we consider is reality. I always like this kind of information because of its philosophical implications: THERE IS NO OBJECTIVE REALITY! Everything we perceive, know and believe to be true is made up in one way or another by our subjective minds. I sometimes wonder what the world would be like, if all of us would live according to such understanding … the optimistic part in me likes to think we would have much more tolerance and acceptance of the other, and therefore less conflict and a more peaceful world …

Back to the cover story titled “Mind Tricks: Six ways to explore your brain”. As the headline suggests, it looks at what scientists just begin to understand as being the workings of our brain; it does that by ‘exploring’ aspects of perception, memory, attention, body image, the unconscious mind and the curious consequences of our brains being split in two. The six posts mentioned below will summarise those findings.

• Discontinuity of perception
• The unreliable body image
• Curious consequences of the split brain

Perceived reality is not at all reality; it’s a stitched up patchwork of selected impressions and guesswork. Take our visual impressions. In the centre of our retina we have a small patch of densely crowded photoreceptors called the fovea. This spot is the only part of the eye capable of seeing with the rich detail and full colour we take for granted. To get an idea of its size: it covers an area of our visual field that is no bigger than the spot the moon takes up in the sky - yet it feeds our visual system with almost all of its raw information.

So how do our eyes build up a picture? Not by continuously scanning our environment but by darting around, by fixating a certain spot 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. During those saccades we are effectively blind; the brain does not process the information picked up in between because the eyes move too rapidly.

Despite their short duration we can actually capture saccades visually. One way is to look in a mirror and flick our focus from side to side; however hard we might try though, we cannot see our eyes move; because the saccade is motion, our brain does not pay attention to it. Another way to catch saccades is the so-called frozen-time illusion: it’s the sensation we get when looking at a clock, the second hand appears to freeze for a brief moment before moving on.

This particular effect is quite interesting because some scientists believe that it partially explains how vision works: to compensate for the temporary shut-down, our brain makes a guess at what it would have seen, and it does so retrospectively. In other words, the 100 or so milliseconds of blindness gets back-filled with the image that appears after the saccade is over; the “second” then lasts about 10 per cent longer than normal, which is enough for us to notice. But it’s not only guesswork that is used to justify the idea of backfilling; short-term and long-term visual memories retaining information from previous fixations are also suggested as ways of filling gaps and creating a continuous here-and-now visual experience (Andrew Hollingworth, Visual Cognition, vol 14, p 781).

It is not only vision though that is affected by discontinuity of experience; our 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. “Phonemic restoration” is the a term to describe how our brain pastes in the sounds that obscured or distorted people’s voices in everyday situations.

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 or parts of the sentence being played reverse, the sentence miraculously becomes understandable (Acoustic Science and Technology, vol 27, p 318); the brain replaces the distortion based on the information in the remaining speech signal (Kashino’s sound files are available here).

It seems that the presence of this speech signal is of prime importance; the brain might not switch to possible speech responding circuits unless it detects spoken language (Hearing Research, vol 229, p 132). Another demonstration for this ability to detect meaning from distorted speech signals is a form of synthesised speech called sine-wave speech. Hearing it first it sound unintelligible, a bit like whistling or birdsongs; 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 below by clicking on the yellow triangles to download the associated wav files; more examples can be found here).

What happens when the two gap filing mechanisms come together? Sometimes the visual and other times the auditory system wins out. Take 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 here. On the other hand, when a team of psychologists showed volunteers on a screen a single flash accompanied by two short beeps, those volunteers saw two flashes (Nature, vol 408, p 788). See the illusion here.

The next post will look at the way the brain creates a body image.

[source: New Scientist]

Here’s another Bozmodo clip, this time boggling my non-mathematical mind totally: a video about “Imagining the Tenth Dimension,” based on a book by Rob Bryanton. Visit http://www.tenthdimension.com/mediali… and http://www.youtube.com/10thdim for more info. … I’ll have to look at it a few more times before I maybe get it .