lol :)
I see a few assumptions in your reply that I'd disagree with off the bat:
1) that learning to use both hands is double the effort.
2) That my intention in promoting kids learn to use both hands has to do with their ability to record information
3) That it takes more time at all, at least when taught from a young age.
Let me explain those points in more detail. To #1 and #3, I find learning to use each hand does not mean you double train on all tasks. Typically once you train your other hand on any fine motor task at all (like writing) then it translates to fine motor skills for other tasks, like drawing. In other words you dont have to learn to write x2, then learn to draw x2, then learn to type x2, etc If you are taught to use both hands on all tasks all the time (switching between them) then you will learn at about the same pace as someone using one hand, once you gain basic motor skills at all.
Now to point #2, well as I covered in the last blip, it isnt about ways to record data, so much as physical skills: hitting a baseball, knitting, climbing a tree, writing, drawing, painting, playing the piano.
The more you train both hands well the better you are at many other similar tasks. When you prefer one hand over the other in most tasks, however, then you wind up at a deficit in physical skill.
Since it is no extra time if done from an early age (and only a minimal amount when learned as an adult) then I'd say it isnt wasted time since the amount of time investment is minimal and the advantages it bestows significant.
Writing is a bit of a unique case. While it doesnt translate hand to hand it also isnt a x2 effort. LEarning a new script with one hand takes a fraction of the time to learn with the other hand if it already is capable of fine motor skills. But the movements are fairly different so there is some relearning.
In the case of handwriting by nature of the fact english is left-to-right writing I tend to recommend learning to use your right hand for that. Only time you'd need to learn the left hand is if you do a right to left script too.
Though its good to learn despite the usefulness due to just training your brain in general.
@freemo @khird @jahnke I guess to make it less inflammatory or context dependent the message can be distilled down to "ambidexterity should be encouraged and rewarded (more)". I for one am often inconvenienced by finding myself with one tired/worn and another weak/fumbley hands, not even sure which one to consider "crippled" at that point... if not both.
@freemo @jahnke
I think handwriting is likely less similar hand-to-hand than you think. I'm right-handed and learning to handwrite Persian (a right-to-left language) gave me a lot of appreciation for the difficulty lefties experience in writing English - the tip of your pen tends to be at an angle where it digs into the paper rather than smoothly brushing against it, you drag your hand through the ink you've just written, etc. It seems probable that the muscle movements to guide a pen along a certain path with one hand are going to be quite different from those to guide it along the same path with the other hand, so much so that it's essentially a different skill.