Handedness is the preference for using either the left or the right side of the body for certain things. People are described as left-handed or right-handed when they prefer to write with their left or their right hand. They may prefer the use of certain hands for certain tasks.
Laterisation is caused because one side of the brain is stronger (more dominant) than the other. The left side of the brain controls the right side of the body and the right side of the brain controls the left side of the body.
Until fairly recently most scientists thought that the reason that humans preferred the left or right sides of their body was because they could speak. Language is controlled by the left side of the brain, so they thought there was a connection between language and laterisation.
The scientists changed their minds when they found that it was not just humans who have laterisation. Many animals have it, too. For example: elephants often have preferences for whether they swing their trunks to the left or the right. Honeybees have right antennas that are more sensitive to smells. Parrots can be left- or right-footed, and some don’t mind (they are “ambidextrous”). Animals as different as chickens and minnows like to look for food with one eye and look out for predators (animals that might eat them) with the other. This seems to help them to do two things at once.
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- Article “Southpaws” by Nora Schultz: New Scientist 1 May 2010 pages 36-39