Week
3 Answer:
Last
week Science Spark looked at right and left-handedness.
We asked you to let us know whether you are left
handed or right handed, and your age. The aim
was to survey how many people in Singapore are
left or right handed, and whether there are more
left handed young people compared to older people
(this will indicate whether left handedness is
on the increase).
From
the results we have collected, 21% of the people
are left handed and 79% right handed. However,
the sample size of this pool is relatively small
so we cannot use it to determine whether there
is an increase or decrease in left-handedness.
Estimates of the prevalence of left-handedness
depend on sex, age, and the cultural/genetic background
of the group of interest. Here are some general
trends, taken from a study by Gilbert and Wysocki
(1992) that surveyed 1,177,507 people:
- Men
are more likely (12.6% of men) to be left-handed
than women (9.9% of women)
- Young
people (i.e. 10-20 years old) are more likely
to be left-handed (14% of men, 12% of women)
than are the elderly (near 6% of both sexes)
- People
of Asian (9.3%) or Hispanic (9.1%) lineage are
slightly less likely to be left-handed than
whites, blacks, or North American Indians.
Left-handedness
has not always been widely accepted. In the past,
left-handedness has been associated with witchcraft
and sorcery, and lefthanders were burned at the
stakes. Although less violent associations exist
today, left-handedness still carries certain stigmas
and parents still want to force their left-handed
children to use their right hands.
How
does left-handedness arise? There is some genetic
link, but not 100%. So even if booth parents are
left handed, the child does not have a 100% chance
of being left-handed. Even for identical twins,
only 76% of the expected 100% identical twins
are both left-handed. Your right hand is controlled
by the left brain, and the left hand is controlled
by the right brain. It has been suggested that
developmental changes affecting the brain can
result in left-handedness.
Left
and right-handedness is not limited to humans
alone. Throughout nature there is a trend towards
either left or right-handedness. For example,
cats and parrots have general tendencies toward
their left paws and claw; rats and monkeys tend
to be right-pawed. Amino acids, the building blocks
of proteins also exist in mirror image forms (i.e.
right-handed and left-handed).
To
find out more, try some of the links below:
http://www.nature.com/nsu/030901/030901-7.html
http://hcs.harvard.edu/~husn/BRAIN/vol2/left.html
http://duke.usask.ca/~elias/left/
http://www.geocities.com/Athens/Acropolis/1684/lefthand.html
Recommended book:
Right Hand, Left
Hand: The Origins of Asymmetry in Brains, Bodies,
Atoms, and Cultures by
Chris McManus
The
WINNER
for this week 3 Science Spark Quiz is:
Mr
Mushahrin Shah
IC: S8623017H
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