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We’ve got identical girls and often rely on their mannerisms and personalities to tell them apart.
If you rely on this too, or hope to, be careful: twins switch personality traits at will.
For example, one of our infant girls would be shy one week while the other was a social butterfly. Just when you thought that was the pattern, they switched and the social standout would cry hysterically with strangers. Go figure.
We’ve seen switching of twin personalities and traits from an early age in all these cases:
- who is a good eater
- who is a wiggle worm
- who wakes up first
- who takes good naps
- who drinks her bottle in one sitting
- who smiles at strangers
- who makes what sounds (when our girls weren’t talking yet)
- who steals toys from the other
So if you want to keep your twins straight, particularly if they are identical, combine multiple data points in identifying each. Combine personality traits and even subtle visual clues to properly identify who is who.
It is fascinating to watch the switcheroo happen. Just keep your eyes open and enjoy the journey.
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Twin dad Todd Courtney observed that his identical twin boys would “flip back and forth” in terms of being empowered or following, with “role reversals that happened throughout their childhood”
Jonathan Snowden, father of twin girls, noted that his daughters, Elizabeth and Lucy, do not “stick to, like, one characteristic or act a certain way” but “interchange with each other”. He explained that one day Elizabeth might be the loud and active one, and the next day Lucy would take on that role, as “they just interchange with each other with their personalities.”
Andy Slinger, a father of identical twin boys, observed that his twins’ personalities would switch over time. He noted that as his boys grew up, they “jumped between different personality types”, with one sometimes being the leader and then the other taking on that role.
What Does the Science Say About Twin Personalities?
Personality is about 50% heritable. Extensive twin studies have consistently found that roughly half of the variance in personality traits is attributable to genetics. This is based on comparing identical twins (who share 100% of their genes) to fraternal twins (who share about 50% of their genes). Identical twins are consistently more similar in personality, even when raised apart, which provides strong evidence for the role of genetics.
The remaining half of personality variance is attributed to “non-shared environment.” This refers to unique experiences that one twin has that their twin does not. These are not shared family events, but individual experiences like different friendships, teachers, illnesses, or even a different reaction to the same shared family environment. This is the key factor that causes even identical twins to have distinct personalities.
I’m noticiing this more and more as my identical twins get older. It’s getting more and more distinctive, and lasts from 2-3 weeks everytime…. then they just snap back.
@Danielle – thanks for sharing the experience with your twins. Each of our girls has some core personality traits that remain constant but they definitely still switch other characteristics back and forth.
This is SOO true!!! We are experiencing it as we speak! For the umpteenth time, our identical twin girls are acting opposite each other and it is crazy!
I dread it because it messes with my head when they do and it seems so intense when it’s opposite actions!
@Penny – It does mess with your head! Enjoy the adventure.
I’m hearing you. I have ID twin boys and just when you think you know which twin is who BAM take this mum they swap
oh Wow! My identical twin grandsons switch personalities regularly. One will brood while his brother socializes, then the other will get his brooding time in while his brother is socializing. We just go with the flow. If I am around them I can tell them apart. I have no clue how I do it, there is obviously something that I’m subconsciously aware of with each of them. However, now that they are older and don’t require as much of grandma’s gushing over them and preferring High School activities instead, I am embarrassed when I ask them “what is your name,” and they smirk and tell me their name. Once they tell me their name my “subconscious twin indentifying mechanism” kicks in, and I know who is who. It’s always so much fun! :)
@Debby – that is fun to watch their similarities and differences!
Nice thanks for sharing we experience this everyday its weird i thought we need an exorcist lol
@Moe – Haha! I know, right? It can be weird!
My twins are doing this as Im reading this. I can tell the day it happens because they are so opposite. It usually lasts about a week.
Good luck with the switching!
This is not an identical twin thing. Our fraternal twins do the same thing, which is how I found this website- searching for answer as to why. It drives me nuts.
@Lynn – that’s interesting your fraternal twins do the same thing!
My fraternal twins switch too!! Their switching lasts for about 2 months though!
Yes my fraternal twin boys does sane thing hence I came searching. Lol
My identical 2-year-old girls do this. But for long stretches at a time. For a long time, twin A was more assertive, aggressive, less obedient and more outgoing and twin B was docile, more passive, super sweet. And literally the week after we had our first parent-teacher meeting where we discussed Twin A’s challenges in the classroom, they switched personalities and have been that way ever since. It is trippy. Keeps us on our toes and is very confusing.
@Darragh – that is interesting timing (right after the teacher meeting). It is like our twins know we are strategizing ways to parent/teach them and they change things on us to keep us off balance.
So our guys used to do this… then things settled for several years. Just now (age 16!!) it happened again! This week, the rude cranky one had become kind and loving, and the one with whom I’ve really bonded over the past few years had become disrespectful and distant – It is the weirdest thing! Now we’re working to bring the despondent one back into the folks while enjoying newfound cuddles and love with the other. :-)
@Vera – thanks for sharing what is happening with your twin teenagers. It is interesting to see that this pattern continues even as the twins get older.