Question: Why do different sides of the brain do different things?

Helen O'Connor answered on 15 Jun 2011:

Scientists think that the hemispheres developed through evolution to keep us alive: so whilst our left “practical” left hemisphere allowed us to get on with general day to day, well known patterns of behaviour, 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 now, 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 is associated with negative emotions, like anger or sadness. This side also helps us tune into the emotions of other people.