Understanding Left-handedness

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Understanding Left-handedness

• Lau Ming Leong Robert
• Poon Cheuk Yi Louise
• Man Tsz Ho Marco
• Chan Pak Hong Gabriel

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Context

1. Definition
2. Assessment of Handedness
3. Genetic Explanations
4. Brain Functioning and Development Differences
5. Characters and Abilities
6. Difficulties in Daily Life
7. Conclusion

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Baseball
Boxing
Paul Gibson
Carmen Basilio
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Fencing
Laura Flessel-Colovic
Fabrice Gazin
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Musician
Sir James Paul McCartney
Riley B. King (B.B. King)
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U.S. Presidents
Barack Obama
Bill Clinton
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• In this presentation, we primarily
• focus on
• Why do left-handers usually seem talented?
• Why are right-handers more common than the left
  ones?

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Definition
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Definition

• Handedness
• -Vagueness in scientific field
• Using one hand to which handles almost all the
  daily matters. (e.g. writing, using chopsticks)
• Dominant / Preferred hand
• ? the more skillful hand
• Each skill involves different muscles and
  different parts of the brain to them

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The Assessment of Handedness

• Edinburgh Handedness Inventory
• Oldfield, 1971
• A inventory of 10 items (originally 20 items)
• Used to assess handedness in a simple way

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Instructions

• Indicate your preferences in the use of hands in
  the following activities
• Make ONE mark for your preference
• Make TWO marks if the preference is so strong
  that you would never try to use the other hand
  unless absolutely forced to
• Make marks for BOTH if you really have
  indifferent preference

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Edinburgh Handedness Inventory

• Writing
• Drawing
• Throwing
• Scissors
• Toothbrush

• Knife (without fork)
• Spoon
• Broom (uppder hand)
• Striking match (match)
• Opening box (lid)

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Scoring Formula

• ( Right Left ) / ( Right Left ) x 100
• Example
• 13 marks for right, 3 marks for left
• ( 13 3 ) / ( 13 3 ) x 100 62.5
• The index should be ranging from 100 to 100

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Result

• A) (- 100) X gt (- 40)
• ? Left handed
• B) (- 40) X ( 40)
• ? Ambidextrous(????)
• C)(40) X ( 100)
• ? Right handed
• X Your score

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Research results from Oldfield in 1970

• N1109 (400 males, 709 females)

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• Genetic Explanations

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Genetic Model of Handedness

• The Right Shift Theory (Annett, 1985)
• A dominant gene (RS) is responsible for a right
  shift (RS) for right handedness and development
  of speech in left hemisphere
• A recessive form of the gene (RS) results in the
  absence of systematic bias to one side

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Why More Right Handedness

• According to the Right Shift Theory, if both
  alleles (RS and RS ) occur equally often in the
  population and if mating is random with respect
  to this gene
• 50 will be RS
• 25 will be RS
• 25 will be RS

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Why More Right Handedness

• People with RS or RS would show a right
  shift and be right-handed
• People with RS would lack any right shift
• Environmental and social effects would
  determine their hand preference.

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Why More Right Handedness

• If any strong environmental or social bias is
  absent, one with RS is expected to have fair
  chance to be left-handed or right-handed
• In Annetts research, about 87.5 people would be
  right-handed (50 RS , 25 RS , 12.5 RS )
  and the rest 12.5 people would be left-handed
  (12.5 RS )

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Family Study of Sidedness

• Stanley Coren and Clare Porac
• Aim Studying families genetically passed on
  their off-springs

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Family Study of Sidedness

• Suppose that we have TWO type of handedness
  genes,
• R right-handedness L left-handedness
• All gene comes in pairs, one handedness gene
  from Mum and
• the other handedness gene from Dad.

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Family Study of Sidedness

• RR right-handed gene from each parent
• LL left-handed gene form each parent
• RL depend on which genes (R or L) is dominant
• Assume R gene is dominant in this study
  because of the vast majority of right-hand
  interviewers.

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• Eleven families studies on handedness between
  1913 and 1982
• No parents is left-handed
• ?10chance will be left-handed
• Only dad is left-handed
• ?nearly the same chance

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• Only mother is left-handed
• ?the chance of being left-handed is 20
• Both parents are left-handed
• ?the chance of being left-handed is 30-40
• 60-70chance that still being a right hander

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Family study of sidedness
DOUBLE
Left-handedness
Mother
Right-handedness

• ResultMother was left-handed , your probability
  of being left-handed was approximately
  doubleDads handedness didnt seem to matter
  that much.

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Study - Left-handedness family

• Kerr family (Scotland)
• Long history of left handedness
• In general population, 9 out of 10 are right
  hander
• In Kerr family, 7 out of 10 are right-handers

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• Brain Functioning
• and
• Development Differences

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Speech areas associated with left hemisphere

• -Brocas Area (Left inferior frontal gyrus area
  44 and 45)
• -Wernickes area (Left superior temporal gyrus
  area 22)
• Nearly all right handlers have speech control in
  their left hemisphere
• Some left handlers do so
• ?Left lateralization( not a mirror image)
• Some left handlers even use language in both
  sides of the brain.

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Brocas area
Wernickes area
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• Characters and Abilities

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General differences

• The slow growing process
• Learning
• ? the number of left-handers is greater in
  groups of learning disabled and dyslexic people
• Criminality and delinquency (Cesare Lombroso,
  1903)
• Billy the kid
• Jack the ripper
• Three times likely a male criminal is left handed
• Five timed likely a female criminal is left handed

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• Personalities
• Abraham Blau (former psychiatrist)
• ? left-handedness was a sign of emotional
  negativism
• Left-handers appear to be more anxious than
  right-handers (less emotionally stable)

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• Interpersonal Adjective Scale (IAS)
• Wiggins, Trapnell, Phillips, 1988
• 64 adjective words list
• With 523 young adults
• Left-handers tend to describe themselves as being
  introverted
• Bashful, shy, aloof,
• distant, unsympathetic,
• cold, quarrelsome

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• Difficulties in Daily Life

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Stereotypes of left-handers

• From Oxford English Dictionary
• French ? gauche
• German ? linkisch
• Spanish ? zurdo
• Italian ? manico
• Russian ? levja
• Latin ? luft

NEGATIVE
Those above words are negative meaning such as
clumsy, doubtful, illegitimate, questionable, and
even relate to devil.
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Differences between left- and right-handedness
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Tools for Left-Handers
Video
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Difficulties in Daily Matters
Video
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• Conclusion

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• Why do left-handers usually seem talented?
• - Graphical ? combination (brain function)
• ? higher probability to be
  Ambidextrous
• b) Why are right-handers more common than the
  left ones?
• - Genetic reason

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Supplement

• National Left-hander day
• 13th August
• Left-Handers Club
• Formed in 1990
• http//www.lefthandersday.com/

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References

• Annett, M. (1998). Handedness and cerebral
  dominance The right shift theory. The Journal of
  Neuropsychiatry and Clinical Neurosciences, vol
  10, pp 459-469.
• Springer, S. P. Deutsch, G. (1997). Left brain,
  right brain perspectives from cognitive
  neuroscience. W. H. Freeman and Company.
• Laccino, J. F. (1993). Left brain-right brain
  differences inquiries, evidence, and new
  approaches. Lawrence Erlbaum Associates, Inc.
• Oldfield, R. C. (1971). The assessment and
  analysis of handedness The Edinburgh Inventory.
  Neuropsychological, vol 9, pp 97-113.
• Norden, Jeanette (2007). Understanding the Brain.
  The Teaching Company, 2007