Ambidexterity is the state of being equally adept in the use of both left and right appendages (such as the hands). It is one of the most famous varieties of cross-dominance. People that are naturally ambidextrous are uncommon, with only one out of one hundred people being naturally ambidextrous. The degree of versatility with each hand is generally the qualitative factor in determining a person's ambidexterity.In modern times, it is more common to find people considered ambidextrous who were originally left handed and who learned to be ambidextrous, either deliberately or during childhood institutions such as schools, or jobs where right-handed habits are often emphasized or required. Since many everyday devices (such as can openers and scissors) are asymmetrical and designed for right-handed people, many left-handlers learn to use them right-handedly due to the rarity or lack of left-handed models. Thus, left-handed people are much more likely to develop motor skills in their non-dominant hand than right-handed people (who are not subjected to left-favoring devices). Right-handers may become ambidextrous due to an injury of their right hand or arm. Ambidexterity is often encouraged in activities requiring a great deal of skill in both hands, such as knitting, typing on a computer, juggling, swimming, percussion, keyboard music, baseball, paintball, lacrosse, surgery, boxing, martial arts, Parkour and basketball.