Based on the discussion in the comments here:

Is being left-handed going to be more difficult for my son?

Some of us are interested in knowing when hand dominance becomes firmly established.

I'm looking for a general timeline of the related developmental milestones. I know that there's ambiguity and fluidity regarding handedness in young children, but I'm not positive on when the switching becomes less common, and when it zeroes in on one or the other.

Some reports are that it happens quite early, but when 90% of the population ends up being right-handed, I think it's a bit of a self-fulfilling prophecy. Some research suggests it actually happens quite late. I'm not sure if there's more to back up/refute the information found here.

Both of these:

are related questions, but discuss the how/why, not the when.

  • 1
    @Dariusz We're both getting the same type of answers, although I want research not observation. Probably better off closing as dupe and I'll do my own research
    – user11394
    Commented Jun 6, 2016 at 11:58

3 Answers 3


See this article: http://www.encyclopedia.com/topic/handedness.aspx

Infancy In his pioneering work on child behavior, the American developmental psychologist Arnold Gesell claimed that infants as young as four weeks display signs of handedness and that right-handedness is clearly established by age one. However, it was as of 2004 commonly believed that babies are born ambidextrous. Although a hand preference may seem apparent towards the end of the first year, this is not necessarily due to right- or left-handedness and may change several times over the subsequent few years.

Toddlerhood Toddlers usually go through phases of using one hand for some activities and the other hand for other activities. Although many children exhibit clear left- or right-handedness from the age of two—and handedness usually is determined during the third year—it is not unusual for a child to repeatedly switch hand preferences well into their preschool years. Early hand preference may be due to a pathological problem (e.g. stroke ).


Our pediatrician told us that you can often tell which hand a baby will prefer by watching which hand it brings to its mouth most often, especially for a self-soothing effect. She even claims that if you watch a baby in utero long enough, you can observe the same phenomenon before some babies are born.

I don't have any scientific proof, but it has held true for all five of my kids (only one of which is left handed). So my answer is anecdotal, but I thought you might find it interesting to consider.


Another anecdote. I have fraternal twin boys. They were ambidextrous through the first year or so. I had a suspicion that one was left-handed, but he wasn't reliably left-handed. Going into year 3, one is reliably right-handed. The other one tends to left-handedness but will happily eat, brush his teeth, or draw using either hand. So I'm still not sure which he'll end up as!

"reliably" = almost always using the same hand for a task.