Also in this week's column:

• If whales can communicate by telepathy, why can't humans?
• Why do we like to scratch a wound when it's healing?

You think you know about the brain?

• Korsakoff's Syndrome is an inability to form new memories because of damage to the brain's temporal lobes after years of alcohol abuse. Sufferers make up stories and then make up new stories to cover the mistakes and falsehoods in the first series of stories.

  According to Drs G d'Ydewalle and I Van Damme of the Department of Psychology at the University of Leuven in Belgium, writing in the Neuropsychologia (Epub September 2006), the "more critical" problem Korsakoff's sufferers face is a "deficient involuntary conscious memory". Nevertheless, they perform much better in memory tests when "guessing" is allowed.

• More electrical impulses are generated in one day by a single human brain than by all the telephones in the world.
• It is estimated that on an average day the human brain produces 70,000 thoughts.
• Women's brains are smaller than men's brains by an average of about 12 per cent.
• Arachibutyrophobia is the fear of peanut butter sticking to the roof of your mouth.
• The average adult human brain weighs three pounds and uses 20 per cent of the body's oxygen.
• Abused children have smaller brains. Parts of the brain of a severely abused and neglected child can be substantially smaller than that of a healthy child.
• Babies lose half their neurons at birth. It is estimated that a baby loses about half their neurons before they are born. This process is sometimes referred to as pruning and may eliminate neurons that do not receive sufficient input from other neurons.
• Baby talk increases vocabulary. A study showed that when mothers frequently spoke to their infants, their children learned about 300 more words by age two than did children whose mothers rarely spoke to them.
• Birdsong and human speech have similar characteristics. Like humans, birds learn their complex vocalisations early in life and imitate their adult counterparts to acquire these skills. These two species have evolved a complex hierarchy of specialized forebrain areas where motor and auditory areas interact continuously in order to produce detailed vocalisations.
• The optic nerve exits the retina as a single bundle. The exit point within the retina has no receptor cells. This location forms a blind spot in each eye. We rarely notice these spots because they do not overlap within the image formed by the two eyes. Your ophthalmologist can only detect your blind spots by having you close the eye not being tested.

Stephen Juan, Ph.D. is an anthropologist at the University of Sydney. Email your Odd Body questions to s.juan@edfac.usyd.edu.au

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