A Twins’ Tale
September 6th, 2007As regular readers of my blog already know, I’m an identical twin. It’s a source of constant curiosity to others, probably because there aren’t that many of us - The best estimate I found seems to put identical twins at about .4 percent of the population, or around 1 in every 250 births. Fraternal twins, by contrast, are much more common, at around 2.7 percent of births (around 1 in 37 births). So that means that there are almost 7 times more fraternal twins than identical twins out there. No doubt this is mostly due to fertility drugs, which increase the chance of having fraternal twins greatly, but not identical twins (other than giving you more “shakes of the genetic dice” through In Vitro Fertilization).
A quick biology refresher for those unsure of the difference between identical and fraternal twins: identical twins share all of their genetic material, whereas fraternal twins are like two separate babies growing at the same time. Identical twins are basically clones, while fraternal twins are basically regular siblings.
Since lots of people know all about having a brother or sister, but relatively few know much about having an identical twin, I’m going to focus on that for this article. And it certainly helps to be close to the research material, after all. (Sometimes too close.)
What kind of things are nature’s clones likely to share, then? Seems like an easy enough question, what with twin studies being a staple of psychology research and all. Surprisingly, I had a pretty difficult time finding twin correlations. In an in-depth search, I failed to locate even one authoritative site. (If you find one, please let me know.) Maybe I should write a blog about that instead!
For now, though, you’ll have to settle for this post, and after a fair amount of research I managed to dig up these correlations:
- Freckles (similar in occurrence and number)
- GERD (acid reflux disease) and IBS (irritable bowel disease)
- OCD (obsessive compulsive disorder)
- Autsim
Of course height, weight, and the like are correlated too. (For example, my brother is only a half inch taller than me.) One really interesting correlation I found is that when one twin is left handed, the other is often the opposite (and vice versa). That’s true for me and Ed too. Though me and my brother are both somewhat ambidextrous, he’s definitely a left hander and I’m a rightie.
One thing twins *don’t* share is fingerprints, interestingly enough. Ed used to joke that he could commit crimes and pretend he was me. (And you think YOU’RE paranoid.) He wouldn’t have to worry about DNA evidence, but he better wear his rubber gloves!
If you’ve ever pondered a scenario like that yourself, such flights of fancy are especially common by those who aren’t twins. There are evil twins, sorceror twins, and even a fictional place called Twinwirld, where almost everyone is a twin. They’re certainly interesting, but they vary widely in how well they capture the twin experience as I know it.
Speaking of my perspective, I tell everyone who asks me what it’s like to be a twin the same thing: It’s like a cross between a close friend and a brother (or sister). Part of the family politics are there, but the two of you can treat each other like peers, more or less. If that analogy doesn’t make sense, imagine having a cellmate for life in prison, but in a positive way. Except for the occasional stabbing or fight over a pin-up poster, you would eventually be like family to each other, but not quite. And if THAT still doesn’t make sense, here’s an excellent short story written by an identical twin girl who participated in a California twin study.
I don’t mean to beat a dead horse here. But people’s fascination from twins should be obvious from all the links above, and despite this a great many people seem to lack real insight into what being a twin is really like. For example, a lot of people tell me, “I wish I had a twin.” When pressed, though, many of them seem to think a twin would be like a personal slave or compulsory friend they could get to do whatever they wanted. (I only got away with the personal slave bit in high school. Sorry Ed!)
A lot of people seem to think it would be a really novel experience, too. Truth is, twins are regular people just like anyone else. As far as I can remember, the novelty was never even really present for me. (And Douglas Hofstadter makes much the same point in Twinwirld.) Since you don’t choose to be a twin, the whole situation seems almost accidental to me on the whole.
This point really gets driven home for me through reading about conjoined (Siamese) twins. Most people would say conjoined twins (of any type) lead inferior lives to “singletons”. Parents, doctors, and friends all believe that they are happier and better off separated. And besides, they argue, the abuse and ostracism they suffer is reason enough to risk potentially fatal surgery.
Trouble is, every interview I’ve read with conjoined twins suggests they prefer not separating. Reading what they have to say - as someone who partially shares in their experience - is fascinating to me. Many of these twins say, as I do, that if you’re born that way, it all seems to normal to you. And now that they’ve experienced life, conjoined, they wouldn’t want to be separated even if they could. Even though many of them have to deal with shocking insults and ignorance on a day-to-day basis, conjoined twins often say they’re perfectly happy.
That’s not to say I understand what it’s like to be a conjoined twin. I don’t. Ironically, I find them fascinating in the same way I imagine singletons find regular twins fascinating. For example, here’s an interesting link from Kur5shin about many legal issues involving conjoined twins. They even describe a conjoined twin who was denied a marriage license on the grounds that it would promote group sex! Reading about them dating/falling in love with two different people blew my mind. Can you imagine tuning out while your conjoined twin makes love to their significant other? Apparently it’s possible.
Anyway, there’s plenty of other twin-related issues I could write about. Do twins run in families? Should you separate them at school? Should you dress them alike? What should you name them? But, I’ll save those issues for another post. Right now my main worry is getting my clone Ed to help me edit this post. (Which he did, bless him.)
More twin links:
Ann Landers and Abigail Van Buren, identical twins
Laura and Jenna Bush, presidential twins
Identical twin women have twins much less often than fraternal twins
Women that have twins are more likely to have more
Twin birth rate is rising
Ohio twin convention
Popular twin names (also here)
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September 20th, 2007 at 12:23 am
Another great post. Keep up the good work, Dave.
Thanks for reading and for the kind words!
- Dave
October 5th, 2007 at 8:31 pm
A guy I work with has twin daughters in high school, and he gave them rhyming names! I’ve never asked, but the question has always nagged me: why would he do that to them? It seems like a gag. Not any less so than the names of any of Zappa’s kids though, I suppose.
January 27th, 2008 at 11:29 pm
Cool blog you have. I’m have lots of fun reading it… Pure curiosity: Do you and Ed share temperaments? Is he an INTJ as well?
Hey, thanks for reading Nadine! I appreciate the kind words - no surprise you’re an INFP (the Healer, if I remember right).
To answer your excellent questions, Ed and I probably do not share temperaments. He fancies himself the Teacher, or ENFJ. (Or as far away from you as he could be and still be an Idealist. :)) Makes sense since he taught English in Japan and all. Some time ago I felt much closer to him, as I originally tested as an INFJ (the Counselor). So much so that I got on the INFJ mailing list, which I still receive hundreds of emails from a month. Thus we were extremely similar, except he was the extrovert and I was the introvert. I attribute that to the then recent death of my father, which was a very emotional event that made it hard to be rational, for obvious reasons.
Over time I believe your personality can shift, and I think mine did. Or should I say, I think it returned to the mean, as I have always had a rational streak. As I got further away from my Dad’s funeral, I think my big bleeding heart F got turned back into my more normal cool-headed T. And thus I was back to my more core personality type, INTJ (the Mastermind) where I’ve sat happily ever since. Nowadays I play more of the yin to my brother’s yang, or in our worse moments, fire to his ice.
Anyway, you may want to check out the INFJ mailing list (since it’s so close to INFJ). They have a very unique perspective on things (since you so rarely hear them speak out) and they’re probably about the nicest people I’ve seen online. I haven’t read anything off the list in years (it’s ridiculously time consuming to keep up with), but I plan to go back and read some at some point. And thanks again!
- Dave
January 28th, 2008 at 11:15 pm
Hello Dave,
Thanks for your nice thorough answer.
I must confess, you just threw a wrench into my little theory temperament genetics. I’ve been toying for a while with the idea that temperament must be at least partly genetic. Like you, though to a far less extensive or scientific level, I entertain myself by collecting data on people. I love genetics and also love temperament theory so I’ve been mapping temperament family trees for people I know.
In my current collection of data, I’ve noticed the following trends: two SJ parents mean all kids are SJs. SJ/SP couples get SJ, SP kids most of the time with the odd N thrown in. N/N couples get only N children. This would tend to indicate that the S gene is dominant while the N is recessive. I haven’t really been able to figure out any significant pattern on any of the other characteristics.
So, I expected that if temperament is genetically conditioned, identical twins would be of the same temperament… Clearly that’s not the case… I’m going to have to think about my little model a bit
Thanks for the suggestion on the INFJ mailing list. I’m not a big fan of mass emails though… and rarely participate in forums… I would much rather communicate with people one on one - that comes with being an introvert, I suppose -
cheers,
Nadine
Wow, temperament family trees, eh? That’s actually pretty interesting. I could understand SJs having SJ kids and SJs having SJs/SPs. I can also understand Ns having N kids. But Keirsey himself goes out of his way to say that any two people can have children of any other temperament, which is often the source of parent/child tension.
Still, I think you’re probably right that temperament is part genetics, despite what I’ve said. The problem is I see temperament as a responsive variable over time, with a person only having a vague “tendency” toward a particular personality type (the genetic part). My brother and I have been very alike at times, and other times we seem like we were born on different planets. Plus, many identical twins go out of their way to be different from each other (like me and Ed), so that may play a part.
Then again, you have a lot more practical experience with all this stuff, especially in family contexts, so what do I know? That’s really cool that you profile other families like that. Do you tell them the results? Do you have to explain MBTI/temperament theory to them first? Is it based on them taking personality tests? Or is this some semi-private endeavor that you engage in by yourself as a curiosity? You must really know people (and their families) well to do something like that. Sounds like you have a talent for it.
- Dave
January 29th, 2008 at 4:52 pm
I use my own knowledge to classify people rather than asking them to take a test. I find a lot of people find MBTI type questions confusing/difficult and often answer the question: who would you like to be, as opposed to who are you.
With some practice, you can get get pretty good at it… It’s amazing how powerful a tool the MBTI is when you can use that way. It’s a disturbingly accurate predictor of how people are going to react in a given situation and what they’re going to say. The amazing thing is that this is true regardless of cultural context. I’ve worked in many different countries using several different languages and the MBTI has never failed me…
I think that saying that temperament is a function of genetics and that it is responsive variable over time are not mutually exclusive. It really goes back to the old nature vs nurture argument. My take on this is that the two complement each other to make us what we are. Essentially, our genes would give us some natural aptitudes… while our experience shapes what we do with these aptitudes…
For example, I could have all the right genes to be a top violin virtuoso - I don’t - but if I never pick up a violin, I’ll probably never get very good at it and even maybe believe I’m a poor violinist. Conversely, I might have a natural ability to use my feelings to make judgements and start out doing just that. Then I find out, through a traumatic experience, that giving into these feelings is very painful. I will then use my ability to rationalize more and more… until maybe, if I have the right genes, my comfort level with using thinking and logic to make judgements exceeds my comfort level to make judgement using my feelings.
Also as you pointed out yourself, it often happens that a pair of twins are mirror images of each other - one left handed, the other is right handed -… We know, from scientific studies, that though they have the same genes, both twins do not experience gestation the same way: one twin almost always gets more nutrients and has a developmental advantage over the other… also, one twin always suffers more than the other at birth… so while the experiences of twins raised in the same family are very similar, they aren’t the same. The difference in these experiences accounts for example for why one of the twins might develop schizophrenia while the other does not. Indeed, it turns out that a twin that suffers from oxygen deprivation at birth is nine times more likely to develop schizophrenia that the one who does not. If you’re interested in learning more about this, I suggest you read “The agile gene” byt Matt Ridley. It’s a fascinating book… at least if you’re interested in how nature and nurture interact to make us who we are…
Let me stop here as this comment is starting to turn into a post of my own. This is supposed to be your blog
Feel free to contact me by email if you want to discuss this further. I believe you have my email address.
February 22nd, 2008 at 12:31 am
[…] few months ago I wrote about being an identical twin. Back then I’d done some research on twins, but I really didn’t find out that much. […]