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Believe Your Brain, Not Your Eyes?

By Shlomo Maital


  Fake Hand Experiment

 A BBC Horizon TV documentary presents a fascinating glimpse into research on how our eyes, ears and brain interact.  It presents findings by researcher Beau Lotto and others.  A massive 30 per cent of our brain is occupied by our visual cortex – which interprets what we see.  But sometimes, we can’t always believe what we see, because our brain is so efficient at interpreting (sometimes misleading) contextual clues. 

     In one great experiment, we hear a woman saying the syllable “Bah Bah Bah” clearly.   But at the same time we are shown a video of her saying “Gah Gah Gah”.  What do we believe? Our ears? Or our eyes?    The sound track? Or the video? 

    Our eyes of course.  We respond that she is saying “Gah” when in fact we are hearing “Bah”.   Believe your brain.  Sometimes….

    In another amazing experiment (you need to follow this closely):   Subjects place one arm and hand on a table, visible, and the other (right) hand and arm, on a part of the table blocked by a partition from their vision.  So they can see only their left hand and arm.  Next to that hand and arm is placed a fake rubber hand and arm, visible.  The researcher strokes the visible fake hand with a paint brush, and at the same time strokes the (out of sight) hand with a paint brush, so that the brain establishes a link between the two.   The subjects, of course, feel only the real right hand. 

   But suddenly, the researcher takes a hammer and brings it down hard on the fake rubber hand.  Subjects feel pain, shock and distress!   Why?  They can’t feel the rubber hand!   Well, indeed they can. (At least, 90 per cent of subjects can; 10 per cent feel nothing).  We have mirror neurons – brain cells whose specialty is to feel, literally feel, what others are feeling.  These mirror neurons are crucial, because they help us build empathy, a key component of social skills.    

There is an enormous number of optical illusions, based on our brains employing visual cues from the context of something, rather than the object itself.  It turns out, then, that we can neither (always) believe our eyes, our ears, or even our brains. 


Blog entries written by Prof. Shlomo Maital

Shlomo Maital
May 2012
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