HANDEDNESS By Elizabeth Johnson WHAT IS HANDEDNESS v

HANDEDNESS By: Elizabeth Johnson

WHAT IS HANDEDNESS? v the preferential use of one hand for most fine manual tasks. v reflects the greater capacity of one side of the brain, the individual’s dominant cerebral hemisphere, to carry out skilled motor action.

IS IT GENETIC? http: //www. youtube. com/watch? v=ln. Apgml. JMNA

CHANCE OF LEFT HANDEDNESS v Left-handedness is about three times as common in males as in females. v Statistically one twin in a set of twins has a 20% more chance to be left-handed. v Gay people may be up to 39% more likely to be left handed as straight people.

DEVELOPMENT OF HANDEDNESS v Slowness in developing hand preference or an enforced change from left to right handedness is noted in many, but not all, cases of stuttering. v Last year my mom noticed that the majority of the students that were being tutored in reading were left handed.

LEFT HANDEDNESS v Left handed parents only show a weak tendency to have left handed children. v If both parents are left-handed, 45 to 50 percent of their children will be left-handed (which also means that roughly half will still be right-handed)

AFFECTS OF LEFT HANDEDNESS v Left handedness is associated with prenatal and birth difficulties, like prolonged labor, prematurity, Rh incompatibility and breech delivery. v Authors of a study say that left handed individuals: have a smaller number of offspring, a higher number of spontaneous abortions, lower birth weight, higher rate of serious disorders and a shorter life span. Left-handedness has similarly been linked to neural tube defects, autism, stuttering, and schizophrenia.

AMBIDEXTROUS v The use of both hands equally v Most infants and children are ambidextrous v Then between the ages of two and six one hand the corresponding foot are used more than the other and by middle childhood there is usually no doubt about the dominant side. v True ambidexterity is rare.

TWINS: v twins are more likely to differ in hand preference, more than in regular siblings, this could be a result of them lying in opposite orientations of the uterus.