Can Twins be Left and Right Handed?

Once you become a twin parent, you lose track or the things you wonder before they come or the random questions strangers might ask you from time to time. One of those  is whether they will be left-handed or right-handed. If you are expecting twins then this article might very well be for you.

Numbers and Statistics of Left and Right Hand Preference in Twins

Generally speaking, there’s a very low chance for twins to be left-handed. In fact, less than 10% of the entire population is left-handed. We also know that females on average are more likely to be right-handed compared to males.  So based on this, we can confidently say that there’s a fair chance that your twins will most probably most be right-handed.

We now know that twins can be either left or right handed

Can one Twin be Left Handed and the Other Right Handed?

One interesting thing to note is that there is a 20% chance that one of twins will be left-handed and the other will be right-handed. This proves that hand preference is not entirely a genetic trait, because if it was both twins would always have the same dominant hand.

Why Can Twins Have Different Dominant Hands?

Research has shown that the factors determining the handedness of newborns are both environmental and genetic in nature. This has led to the birth of many theories regarding dominant hands in twins.

Trauma or Stress During Pregnancy?

One prominent theory proposes that left-handedness is a result of trauma or stress in women during birth or pregnancy. Of course, giving birth to twins is more ‘stressful’ than giving birth to a single child, due to the presence of multiple fetuses. Therefore, according to this theory the likelihood of left-handedness occurring in twins, is higher compared to lone children.

Position of the Babies in the Womb?

Another leading theory makes the case that handedness is largely determined by the position of the babies inside the womb. This theory explains the instances in which twins have different dominant hands from each other, as twins most likely lie in opposite directions in the womb.

Brain Hemisphere Development?

Last but not least, there is a leading theory that relates handedness to brain hemisphere development. A more developed left hemisphere, leads to a greater chance of right handedness, and vice versa. Higher levels of testosterone in the womb hinder the development of the brain’s left hemisphere, leading to a greater chance of left handedness. This theory explains why males are more likely to be left-handed than females.


None of the theories presented above are a hundred percent correct, or a hundred percent incorrect. All babies are different and coming up with a universal theory for determining handedness in twins, is nearly impossible. However, research in this domain does provide us significant insight and plausible theories that may explain why your twins ended up having a dominant hand preference.


Just so you know we’re not making this stuff up 😉 Here’s some references for statistics used in this article:


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