Question: What makes us left or right handed and why do younger siblings copy or act like the elder one, ie the younger one being left handed like the older one?

Keith Siew answered on 28 Jun 2013:

Monkey see monkey do!

Regarding copying… the great apes learn by a process of mimicking… and we tend to try mimic those with greater authority… (i.e. the older sibling).

We have things called mirror neurons that allow us to in our brains re-enact a motion we see… so if I see someone kicking a ball… the same neurons that would fire in my brain to kick the ball would also fire in my brain but get inhibited so that they don’t actually make my leg kick… but its the brain’s attempt to understand what’s going on and learn from it! It also gives us a biological basis for empathy… as the neurons can mimic emotions and sensations like pain… that’s why it looks so painful when someone maybe falls over and hits there head cause your brain is recreating it in your head.

Genetics and then some environmental factors in the womb decide right/left handedness… so it can run in families… There was an entire clan in Scotland who were left handed… they built all their spiral staircases going in the opposite direction to make it easier for a left handed person to win the fight and disadvantage the left handed person!