Handedness and Brain Asymmetry: The Right Shift Theory
Brain asymmetry for speech is moderately related to handedness but what are the rules?
Are symmetries for hand and brain associated with characteristics such as intelligence, motor skill, spatial reasoning or skill at sports?
In this follow up to the influential Left, Right Hand and Brain (1985) Marian Annett draws on a working lifetime of research to help provide answers to crucial questions. Central to her argument is the Right Shift Theory - her original and innovative contribution to the field that seeks to explain the relationships between left-and right-handedness and left-and right-brain specialisation. The theory proposes that handedness in humans and our non-human primate relations depends on chance but that chance is weighted towards right-handedness in most people by an agent of right-hemisphere disadvantage. It argues for the existence of a single gene for right shift (RS+) that evolved in humans to aid the growth of speech in the left hemisphere of the brain.
The Right Shift Theory has possible implications for a wide range of questions about human abilities and disabilities, including verbal and non verbal intelligence, educational progress and dyslexia, spatial reasoning, sporting skills and mental illness. It continues to be at the cutting edge of research, solving problems and generating new avenues of investigation - most recently the surprising idea that a mutant RS+ gene might be involved in the causes of schizophrenia and autism.
Handedness and Brain Asymmetry will make fascinating reading for students and researchers in psychology and neurology, educationalists, and anyone with a keen interest in why people have different talents and weaknesses.
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The puzzle of handedness and cerebral speech
Discrete types or continuous
A right shift factor for left cerebral dominance
The single gene theory of right shift
Handedness with age sex and time
A single gene with variable expression for genotype
Other asymmetries of brain and behaviour
The theory of an agnosic
Independent tests and challenges
Alternative theories or variations on a theme?
What how and why?
Notes on the assessment of preferences with
Genotypes of lefthanders righthanders per 1000
Thresholds of the RL continuum measured from
actions AHPQ alleles analysis Annett assessed associated asymmetry atypical autism biases bilateral brain Broca's area cerebral asymmetry cerebral dominance cerebral speech chance chapter chi-square classified consistent right-handers depend dextrality dichotic listening difference disorders dyslexia dysphasia dysphasics evidence expected eye dominance eye preference factor females Figure findings frequency genetic model genotypes groups hand preference handedness heterozygote heterozygote advantage human hypothesis incidences of left-handedness indirect report Ladinos language lateralisation left CD left hemisphere left-handed children left-handers left-writers lesions males McManus mixed mixed-handers MZ twins non-right-handers nonhumans normal distribution numbers observed parental incidences patients pattern paw preferences peg moving percentages phonology poor population predictions primates questionnaire R-L hand skill random relative right CD right hemisphere right shift right-sided schizophrenia scores self-report shows side sinistral spatial ability species speech disorders speech laterality studies subgroup suggested Table theory thresholds twin pairs types variable versus writing
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