I am right-hand dominant.  I use my right hand to write, to cut, to turn the door knob, to scroll on my phone (but I usually use both hands when composing an SMS) and to even hold a gun.

I use my right thumb to press the space bar when typing.  (How about you?)  

One time my thumb was kind of aching (texter's thumb syndrome I suppose) and so I tried tying my right thumb to my index finger buddy tape-style and tried using my left thumb instead for pressing the space bar when typing.  I tell you it is super hard.  My typing speed was cut down to probably more than half.  I was so frustrated because there is this slight nanosecond pause every after word.

I ended up freeing my right thumb and taking pain medication and typing away using my right thumb.  Fail.  I'll try it some other time. ^^

So my challenge for you guys, try it!  Use your non-domninant thumb to press the freaking space bar.  Try it!

(I'm hoping I'm not the only one who will find this really difficult.) ^^