# Identical Twins: One's always left-handed, one's always right. **URL:** \ **Category:** Factual Questions\ **Created:** [October 1, 2001, 12:10am UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680 "2001-10-01T00:10:52Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![davejg](https://avatars.discourse-cdn.com/v4/letter/d/ec9cab/32.png) [@davejg](https://boards.straightdope.com/u/davejg)\ **Post date:** [October 1, 2001, 12:10am UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/1 "2001-10-01T00:10:52Z")
Okay, I know this is bunk, but a co-worker told me that in identical twins, one is always left-handed, and the other is always right-handed. She’s read this in a number of different places. You see, she thinks she might be left-handed because she “absorbed her twin”. It sounds like bunk, and I think I would have heard of this by now if it was a fact. Anyone heard of this? Any reputible links that I can give her to show it’s bunk would be real nice. ---
**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\ **Post date:** [October 1, 2001, 12:22am UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/2 "2001-10-01T00:22:08Z")
[http://boards.straightdope.com/sdmb/showthread.php?postid=1571074#post1571074](http://boards.straightdope.com/sdmb/showthread.php?postid=1571074#post1571074) > [@](#): > > But identical twin concordance for handedness is far from 100%…in fact it is rather low. Many identical twins are opposite in terms of hand dominance, which raises the question of neurological “mirroring.” Notice **Neurococ** says _many_ not _all_. ---
**Author:** ![samclem](https://avatars.discourse-cdn.com/v4/letter/s/a9a28c/32.png) [@samclem](https://boards.straightdope.com/u/samclem)\ **Post date:** [October 1, 2001, 12:33am UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/3 "2001-10-01T00:33:36Z")
You can’t trust those **Neurococ’s** 😃 ---
**Author:** ![Caprese](https://avatars.discourse-cdn.com/v4/letter/c/a9a28c/32.png) [@Caprese](https://boards.straightdope.com/u/Caprese)\ **Post date:** [October 1, 2001, 12:34am UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/4 "2001-10-01T00:34:50Z")
FWIW,both my mom and her twin were right-handed. ---
**Author:** ![GuanoLad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/guanolad/32/42_2.png) [@GuanoLad](https://boards.straightdope.com/u/GuanoLad)\ **Post date:** [October 1, 2001, 1:03am UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/5 "2001-10-01T01:03:19Z")
I have cousins who are mirror twins. Left handed, right handed, part their hair on opposite sides, that sort of thing. Otherwise they were close to identical except for subtle facial structure variation. So it’s hardly standard, and in fact is probably pretty rare. ---
**Author:** ![capybara](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/capybara/32/202_2.png) [@capybara](https://boards.straightdope.com/u/capybara)\ **Post date:** [October 1, 2001, 2:24am UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/6 "2001-10-01T02:24:21Z")
Always need to make an anecdotal appearance in twin threads-- my twin sister and I (identical) are both righties and part, etc, on the same side. ---
**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\ **Post date:** [October 1, 2001, 9:25am UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/7 "2001-10-01T09:25:20Z")
> [@](#): > > \*Originally posted by samclem \* > \*\*You can’t trust those **Neurococ’s** 😃 \*\* Oh, dear. I even previewed, so I have no excuses. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [October 1, 2001, 9:40am UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/8 "2001-10-01T09:40:19Z")
> [@](#): > > \*Originally posted by davejg \* > **You see, she thinks she might be left-handed because she “absorbed her twin”.** What does she mean by that? And is that something a doctor told her? ---
**Author:** ![mongrel\_8](https://avatars.discourse-cdn.com/v4/letter/m/e274bd/32.png) [@mongrel\_8](https://boards.straightdope.com/u/mongrel_8)\ **Post date:** [October 1, 2001, 3:25pm UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/9 "2001-10-01T15:25:41Z")
Isn’t always that the left-handed identical twin is pure evil? ---
**Author:** ![davejg](https://avatars.discourse-cdn.com/v4/letter/d/ec9cab/32.png) [@davejg](https://boards.straightdope.com/u/davejg)\ **Post date:** [October 1, 2001, 3:37pm UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/10 "2001-10-01T15:37:08Z")
* * * ## Originally posted by davejg You see, she thinks she might be left-handed because she “absorbed her twin”. What does she mean by that? And is that something a doctor told her? It was something she’s “read in a number of places.” ---
**Author:** ![Kid\_Gilligan](https://avatars.discourse-cdn.com/v4/letter/k/b19c9b/32.png) [@Kid\_Gilligan](https://boards.straightdope.com/u/Kid_Gilligan)\ **Post date:** [October 1, 2001, 3:44pm UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/11 "2001-10-01T15:44:21Z")
**davejg** originally wrote: > [@](#): > > Any reputible links that I can give her to show it’s bunk would be real nice. The question I have is, “Why should we believe that someone who believes she ‘absorbed her twin’ would listen to a reputable link?” ---
**Author:** ![booklover](https://avatars.discourse-cdn.com/v4/letter/b/85f322/32.png) [@booklover](https://boards.straightdope.com/u/booklover)\ **Post date:** [October 1, 2001, 4:30pm UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/12 "2001-10-01T16:30:48Z")
Regarding the “twin absorption” thing—there are a fair number of people in medical history who have a “partial” twin attached to them (in other words, a set of twins that simply didn’t fully separate & develop properly). I’ve also seen this referred to as having a parasitic twin—check out the out of print book entitled “Very Special People”. It’s essentially a history of “freaks” in the circus, among them a number of people with the aforementioned condition. Saw something on unusual medical conditions (PBS) which featured a man who had a second, partial face on the side of his head that made its own faces (independent of the main man’s feelings/expression). Very creepy. Maybe this woman has some kind of hidden “thing” that gives her reason to believe she had a twin. ---
**Author:** ![half\_a\_person](https://avatars.discourse-cdn.com/v4/letter/h/8797f3/32.png) [@half\_a\_person](https://boards.straightdope.com/u/half_a_person)\ **Post date:** [October 1, 2001, 5:37pm UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/13 "2001-10-01T17:37:37Z")
From Cerebral mirror-imaging in a monozygotic twin. Lancet. 354(9188):1445-1446, October 23, 1999 : “Mirror imaging is estimated to occur in 25% of monozygotic twins.” – michael ---
**Author:** ![Cerowyn](https://avatars.discourse-cdn.com/v4/letter/c/82dd89/32.png) [@Cerowyn](https://boards.straightdope.com/u/Cerowyn)\ **Post date:** [October 1, 2001, 6:27pm UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/14 "2001-10-01T18:27:08Z")
I’d like to elaborate on what **half a person** (and if that isn’t an ironic name for this thread, I don’t know what is) posted. From the [Parents of Multiples](http://www.twinstuff.com/default.htm) website: > [@](#): > > Mirror-Image Twins are identical twins that scientists believe split later in the embryonic stage than usual. When the cluster of cells do finally split, there is already a formed right side and formed left side with one twin developing from each side. There are even medical examples where one mirror-image twin has internal organs on the right side of the body and the other on the left. For anyone who has or is having multiples, from experience I can recommend POMBA (Parents of Multiple Birth Association) as a great resource! ---
**Author:** ![shelbo](https://avatars.discourse-cdn.com/v4/letter/s/3d9bf3/32.png) [@shelbo](https://boards.straightdope.com/u/shelbo)\ **Post date:** [October 1, 2001, 9:03pm UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/15 "2001-10-01T21:03:46Z")
> [@](#): > > \*Originally posted by GuanoLad \* > \*\*I have cousins who are mirror twins. Left handed, right handed, part their hair on opposite sides, that sort of thing. Otherwise they were close to identical except for subtle facial structure variation. > > So it’s hardly standard, and in fact is probably pretty rare. \*\* I always figured that the side you part your hair on depends on which hand holds the brush. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [October 1, 2001, 10:14pm UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/16 "2001-10-01T22:14:29Z")
> [@](#): > > \*Originally posted by davejg \* > \*\*It was something she’s “read in a number of places.” \*\* Still unclear about this; she read that **she** ‘absorbed her twin’, or she read that it’s not impossible and **thinks** this is the case, or does she have some solid evidence that this might be the case? 😕 In any case, from what I read, absorption of a twin doesn’t mean that the brain/personality of the two individuals merges, just the bodies. ---
**Author:** ![fiddlesticks](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fiddlesticks/32/18129_2.png) [@fiddlesticks](https://boards.straightdope.com/u/fiddlesticks)\ **Post date:** [October 1, 2001, 10:16pm UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/17 "2001-10-01T22:16:25Z")
My mother and her twin brother are fraternal twins (obviously!) but are oppositely handed. Mom always said that this was because her right side was crowded out in the womb so she developed as a lefty. But my Mom ain’t a scientist so take that with a grain of salt, but it seems from the previous posts that handedness is not a strict genetic trait. ---
**Author:** ![slipster](https://avatars.discourse-cdn.com/v4/letter/s/df705f/32.png) [@slipster](https://boards.straightdope.com/u/slipster)\ **Post date:** [October 1, 2001, 10:51pm UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/18 "2001-10-01T22:51:59Z")
There are, in fact, three types of twins: fraternal, identical and (the rarest) symmetrical or “mirror”. Fraternal twins occur when there are two ova in the womb and both are fertilized. Aside from being the same age, frternal twins are no more similar than any other pair of siblings. Identical twins occur when the fertilized ovum splits into two surviving parts early in its development. Symmetrical or mirror twins occur the same way, except that the split happened differently, so that one of the two halves got turned around, and developed “in reverse”. One can, arguably, classify mirror twins as a sort of subset of identical twins. In the case of mirror twins, one is left-handed and the other is right handed. One has the pulmonary muscle to the right side of the heart, so that his or her pulse can be felt on the right side of the chest. There is an ABC soap opera (I don’t remember which one, not being a daytime drama fan), which has (or used to have) an actress who was a mirror twin. Her sister appeared from time to time on the show. There was a character called the “Bay City Strangler” or some such on the program for a while about ten years back, and there was a cliffhanger where it appeared that the regular character had been murdered. Eventually it developed that, instead, her sister had paid an unannounced visit and had been killed in her place. The two characters–like the two actresses in real life–could be distinguished by the fact that one had a birthmark on the right side of her face, and the other had it on the left. “Absorbing” a twin would not turn one left-handed. Either one would develop an autosome (an extraneous growth, like a great ugly tumor" or a parasite (like an autosome only grosser), or, as happens in the great majority of cases, you would simply have a few extraneous cells here and there that you never notice or even have reason to suspect. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [October 1, 2001, 11:07pm UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/19 "2001-10-01T23:07:46Z")
Trouble is, you’ll never find information to debunk **every** crazy idea that people can possibly cook up. Might be better just to say “mmm” and leave it at that, she is your mother, after all. ---
**Author:** ![Dirty\_Dingus\_McGhee](https://avatars.discourse-cdn.com/v4/letter/d/b38774/32.png) [@Dirty\_Dingus\_McGhee](https://boards.straightdope.com/u/Dirty_Dingus_McGhee)\ **Post date:** [October 1, 2001, 11:16pm UTC](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680/20 "2001-10-01T23:16:54Z")
I’m an identical twin and both of us are left-handed. I’m pretty sure the chances are exactly the same as with any normal baby as to which hand they’ll use more. [Next page](https://boards.straightdope.com/t/identical-twins-ones-always-left-handed-ones-always-right/84680.md?page=2)