What Determines Right/Left Handedness?

how old is your child? side preference shouldn't appear strongly until sometime around 12-18 months. My good friend's son showed a strong preference around 8 months and it turned out that he had cerebral palsey and a cyst was causing his brain to shift out of place and that was causing the side preference. If I were you, I'd look a bit further into side preference and when it normally appears.

There is some thought that ultra sound exposure can contribute to a left hand preference.

We were wondering about this too...I am ambidextrous, dh is a right-hander, and Charlie seems to be showing a preference for her left hand - she will reach out with that one, and feed herself, *but* she will wave and play pattycake with the right one! I guess it's one of those things that isn't 'hardwired' yet for them...interesting though. Would love to find out more about it...

I've read recently that handedness is an inborn trait, but it's not fully expressed until the preschool years.

Right now my 11mo goes through phases. For a few weeks she prefers to use her left hand, then she switches. She's been going back and forth like this for a few months now. She sucks her left thumb, though, so I'm pretty sure she will be right handed.