handedness and cerebral lateralisation

Question 1

what is ‘handedness’

Answer 1

the WRITING hand of a person, not correlated with other abilities/tendencies eg grasp or folding arms- behavioural assymetries

Question 2

left-handedness stats

Answer 2

‘Watham forest 96; large scale study of children; LH is ‘10% so lot less prevalence
ratio 5:4 M:F
‘MA showed asians are less LH
‘average IQ lower, more musical, and more mathematical
‘not linked to pathological handedness

Question 3

what evidence is there for RHD over time?

Answer 3

Coen; 70-90% people used RH from 3000bc, lookngat historical artifacts, paleolithic records and ethnographic records
Toth 85: early ancestors 1;5-2mil years ago; used RHD shown in rock/tool trajectory

Question 4

Is this unique to humans?

Answer 4

mice seem tto be 50% dominant, and chimps maybe more RHD (60%) but no where near human domimance, so yes.

Question 5

Who argued for a nurture approach to RHD?

Answer 5

Plato, said it was a result of teaching people to use right hand

Question 6

Aristotle said..

Answer 6

RHD due to nature; superior by natural distinction

Question 7

what evidence is there for twin correlations and innateness of RHD?

Answer 7

Twins have concordance of 75% RH, 21% discordanta and 3% LH

• Foetuses suck right hand in womb and correlate to when out so innate not learnt
• HE parents; 2RH; 9.5%; 1RH; 19.5%, 2LH; 20%.

Question 8

Explain mendalian genetics (mcmanus 9)

Answer 8

2 alleles: domiant: D (dextrous/R), recessive: C (chance/ L) DD: 100%. DC: 75%
grandparnets: 2RH grandparents predicts 10.4%, 1LH gp=15-20% LH

Question 9

evidence against handedness lateralisation?

Answer 9

nearly 80% have bilateral handedness (Taylor and Taylor 90) and no one is ‘left brain only’ unless had a hemispheroctomy (Goswami 06)

Question 10

what does cerebral lateralisation mean?

Answer 10

brain function is dominated by one side of the brain, Grodinsky – very lateralised for some aspects eg grammar and syntax; and language function

Question 11

what techniques are good for measuring handedness?

Answer 11

• fMRI is good for seeing function
• dichotic listening task isn’t effective
• functional transcranial doppler: ultrasound beamed through middle of cerebral artery; shows doppler shift

Question 12

Knecht 2000

Answer 12

used function transcranial doppler: 326 healthy participants right hemisphere dom linearly increased with degree of LH– 4% in RH, 15% in ambiguous, 27% in LH. natural phenomenon of relationship.

Question 13

Schonweisner 05: ear preference

Answer 13

also shown in r/l ear preferance; domiance for processing auditory on one side- assymetric processing shown by fmri

Question 14

How might this differ for different languages?

Answer 14

Eviatar- reading arabic may lateralise as depends on local features which are specific to left side; right is global

Question 15

gender differences in lateralisation?

Answer 15

males more lateralised than females (Tomasi 12)- but challenged by nielson 13 using mri

Question 16

Rogers 90– animal study

Answer 16

lateralisation provides an adaptive advantage- share load and localise function; exposed chicks to light before hatching and able to control brain and eyes separately to feed and watch for danger simultaneously.

Question 17

support of differences in ability?

Answer 17

Choudhary: Left more likely to develop PTSD
American Journal of psychiatry: more likely to be creative, but 10% lower salary (wall st journal)
SAGE journal; 20% correlation with psychosis and SCZ are 40% left handed