• Question: why do brains have two halves, and why is information crossed over?

    Asked by hilmyrwh to Helen, Jenni, Mark, Martin, Stu on 24 Jun 2011.
    • Photo: Helen O'Connor

      Helen O'Connor answered on 24 Jun 2011:

      http://ias.im/48.779

      Scientists think that the two sides of the brain (the left and right hemispheres) developed through evolution to keep us alive: so our “practical” left hemisphere allowed us to get on with general day to day, well known tasks and patterns of behaviour, and our right hemisphere developed out of the need to be aware of our wider surroundings and to sense things like predators in our peripheral vision, and then react quickly.

      So through evolution, we have two very distinct hemispheres:

      The left is technical and linear, and specialises in helping us do things that we do a lot of the time (that we don’t have to think about too much): so it deals with speech and language and mathematics problems like calculation. It also helps us perform familiar movements like writing or making a hot drink.

      The right is more visual and spatial and is involved in helping us with new situations and tasks: we use the right hemisphere for mathematics problems like geometry, or for working out how to do new movements that have a visual element, like building a tower of bricks or fitting a puzzle together.

      The biggest difference between hemispheres is in emotions. We use the left hemisphere to process positive emotions like happiness and to control our emotions, so we don’t have huge outbursts for every emotion we experience. The right hemisphere deals with negative emotions, like anger or sadness and also helps us tune into the emotions of other people.

      The corpus callosum is a bundle of nerve fibres that send messages between the two sides of the brain. The reason information needs to cross over is that we process different types of information on each side. So, for instance, when you start doing a maths problem you might use the left side of your brain as it looks like simple calculation – then you realise its a trigonomotery question, so you might want to bring in your right hemisphere to help “picture” the problem.

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