Clap your hands in front of your nose. Now cross your hands and touch your left ear with your right hand and with your left hand touch your nose. Clap again and switch over hands i.e. touch the right ear with your left hand and touch your nose with your right hand. Do this ten times. Rather difficult isnŐt it?
This movement requires you to use both brain hemispheres simultaneously. From this you can conclude that it is not an automatic response to use both brain hemispheres simultaneously, but a developed or learned response. This demonstration illustrates the value of development.
All people can learn to utilise both brain hemispheres simultaneously, but this will not happen automatically. It can only happen through the right development. Some people use both brain hemispheres, but the dominant brain hemisphere is still preferred and used more than the non-dominant hemisphere. The ideal is for a person to use both brain hemispheres simultaneously and equally.
http://www.neuro-link.org/Brain%20Information/Using_both_sides.aspx