Why are some people ambidextrous?

[petrushka.googol]

Earlier an over simplistic assumption was that equal development of both the hemispheres of the brain was directly related to the ability to use both hands equally well. This seems specious at best because if that was true then no specific talent could be registered in ambidextrous individuals. What is the current insight into this subject?

 

Thanks in advance.

[Ophiolite]

Well, on the one hand......

[iNow]

Handedness appears to be strongly correlated with brain lateralization, specifically which hemisphere is dominant for language ability (left hemisphere dominance for communication tends to correlate to right handedness whereas right hemisphere dominance for communication ability tends to correlate to left handedness).

 

It seems reasonable to me to suspect that ambidextrous people have similar communicative strengths and abilities across both hemispheres of the brain instead of the more common dominance in just one. Most likely, they express less lateralization of the hemispheres than most others.

 

However, one must be very cautious not to attribute something to an absence of brain lateralization when simple conditioning and training remains an entirely possible and valid explanation (i.e. it may just be that these people practiced using both hands to build the skill and have no relevant cortical differences from the general population).

 

 

http://www.apa.org/monitor/2009/01/brain.aspx

handedness has its roots in the brain—right-handed people have left-hemisphere-dominant brains and vice versa <snip> 95 percent of righties have brains that strictly divvy up tasks: The left hemisphere almost exclusively handles language and speech, the right handles emotion and image processing—but only about 20 percent of lefties have brains that divide up these duties so rigidly.

<...>

About 90 percent of people are right-handed, says Corballis. The remaining 10 percent are either left-handed or some degree of ambidextrous, though people with "true" ambidexterity—i.e., no dominant hand at all—only make up about 1 percent of the population.

However, according to this article there are some other complexities there to note and the above may be over-simplified to the point of inaccuracy: http://www.sciencedirect.com/science/article/pii/S0028393208000675

[zapatos]

'I'd give my right arm to be ambidextrous.' --- Yogi Berra

[Ringer]

I'll try to find some papers later, but from what I remember handedness seems to be largely environmental (eg genetic correlations tend to be very weak). Being left handed is a pain in the @$$, the world is backwards (power tools always want to kill you), so it would be interesting that handedness isn't genetic.

[dimreepr]

I think everyone is ambidextrous unless one side has Physiological issues.

We naturally tend towards a hand and then generally never bother with the other, unless circumstances dictate, a broken arm perhaps; if we were made to practice with each hand, writing for instance, from a young age we would all be ambidextrous, admittedly one side would be neater, so it depends on how it’s defined i.e. how equal does each side have to be?

[petrushka.googol]

how equal does each side have to be?

 

Symmetric...

[dimreepr]

By that standard, maybe, no one is truly ambidextrous.

[arc]

Handedness appears to be strongly correlated with brain lateralization, specifically which hemisphere is dominant for language ability (left hemisphere dominance for communication tends to correlate to right handedness whereas right hemisphere dominance for communication ability tends to correlate to left handedness).

 

It seems reasonable to me to suspect that ambidextrous people have similar communicative strengths and abilities across both hemispheres of the brain instead of the more common dominance in just one. Most likely, they express less lateralization of the hemispheres than most others.

 

http://www.classroomhelp.com/lessons/Presidents/garfield.html

 

 

"Garfield was the first ambidextrous president. He could even write Greek with one hand while writing Latin with the other."

 

 

However, one must be very cautious not to attribute something to an absence of brain lateralization when simple conditioning and training remains an entirely possible and valid explanation (i.e. it may just be that these people practiced using both hands to build the skill and have no relevant cortical differences from the general population).

 

 

http://books.google.com/books?id=pX92AAAAMAAJ&pg=PA349&lpg=PA349&dq=Thomas+Jefferson+was+ambidextrous&source=bl&ots=onnP5Z-X8a&sig=ZkxmN14QQGWSvyoPqA1iXM7IDoo&hl=en&sa=X&ei=bKDuUo-1NtjeoASXpYDwDw&ved=0CFwQ6AEwBQ