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Thanks to certain recent events, I wanted to have you guys look at an excerpt from Judith Rich Harris’s The Nurture Assumption. This is here to serve as a reminder to certain people (you know who you are, if not, don’t worry):
In Chapter 3 I recounted some stories of identical twins separated in infancy and reared in different homes. The Giggle Twins, both inordinately prone to laughter. The two Jims, who both bit their nails, enjoyed woodworking, and chose the same brands of cigarettes, beer, and cars. The pair who both read magazines back to front, flushed toilets before using them, and liked to sneeze in elevators. The pair who both became volunteer firefighters. There was also a pair who, at the beach, would only go into the water backward and only up to their knees. And a pair who were gunsmiths, and a pair who were fashion designers, and a pair who had each been married five times. These are not the imaginings of tabloid journalists; they were reported by reputable scientists in reputable journals. And there are too many of these stories for them all to be coincidences. Such spooky similarities are seldom found in the case histories of fraternal twins separated in infancy and reared apart.5
Behavioral genetic studies have proved beyond a shadow of a doubt that heredity is responsible for a sizable portion of the variations in people’s personalities. Some people are more hot-tempered or outgoing or meticulous than others, and these variations are a function of the genes they were born with as well as the experiences they had after they were born. The exact proportion— how much is due to the genes, how much to the experiences—is not important; the point is that heredity cannot be ignored.
But usually it is ignored. Consider the case of Amy, an adopted child. It wasn’t a successful adoption; Amy’s parents regarded her as a disappointment and favored their older child, a boy. Academic achievement was important to the parents, but Amy had a learning disability. Simplicity and emotional restraint were important to them, but Amy went in for florid role-playing and feigned illnesses. By the time she was ten she had a serious, though vague, psychological disorder. She was pathologically immature, socially inept, shallow of character, and extravagant of expression.
Well, naturally. Amy was a rejected child. What makes this case interesting is that Amy had an identical twin, Beth, who was adopted into a different family. Beth was not rejected—on the contrary, she was her mother’s favorite. Her parents were not particularly concerned about education so the learning disability (which she shared with her twin) was no big deal. Beth’s mother, unlike Amy’s, was empathic, open, and cheerful. Nevertheless, Beth had the same personality problems that Amy did. The psychoanalyst who studied these girls admitted that if he had seen only one of them it would have been easy to fetch up some explanation in terms of the family environment. But there were two of them. Two, with matching symptoms but very different families.
(pp. 276-277, emphasis mine)
There you are. Yet how many armchair psychoanalyses have you seen about Santa Barbara murderer Elliot Rodger, blaming some or another aspect in his life for his rampage, including his parents? And these are from people who know about heredity and hence should fucking know better! We can all point to some aspect in someone’s life circumstances we think is the thing (or things) that led to whatever outcome they happen to have. But as this should make clear, it is not so simple. That’s the whole reason behavioral genetic methods were invented!
On that, I refer you once again to this video (from here) featuring behavioral geneticist Nancy Segal (as previously seen in my post No, You Don’t Have Free Will, and This is Why). Pay close attention to the tests the twins had to take:
Indeed, as featured lately in Segal’s recent article about reunited twins:
Consider the case of the identical twin Brent Tremblay. Inadvertently switched with another baby at birth, Mr. Tremblay grew up with adoptive parents and their adopted son, while his twin brother, George Holmes, was raised by their biological parents with a child the family believed to be his fraternal twin. In a remarkable twist of fate, the real twins met by chance at age 20 and eased into a friendship that Mr. Trembley described as “natural and effortless.” They were friends for more than a year before discovering they were twins.
Imagine that you are agonizing over a choice — which career to pursue, whether to get married, how to vote, what to wear that day. You have finally staggered to a decision when the phone rings. It is the identical twin you never knew you had. During the joyous conversation it comes out that she has just chosen a similar career, has decided to get married at around the same time, plans to cast her vote for the same presidential candidate, and is wearing a shirt of the same color — just as the behavioral geneticists who tracked you down would have bet. How much discretion did the “you” making the choices actually have if the outcome could have been predicted in advance, at least probabilistically, based on events that took place in your mother’s Fallopian tubes decades ago?
Of course, none of this is to say (contrary to the accusations repeatedly leveled against me) that “genes are everything.” Though identical twins aren’t actually genetically identical, there are other factors, such as developmental stochasticity (noise) in utero, pathogenic and other biological insults, and plain old randomness that contribute to the differences between twins – and hence, the differences between all individuals. As well, the situation at hand (and the incentives in play) are also hugely important. Genes are the cards in your hand; the landscape of the day is the rules of the game.
But , this should make clear the foolhardiness of trying to identify causal factors – especially those from life experience – that are responsible for any given individual’s behavior. How interesting would it be if Elliot Rodger had a twin brother with similar difficulties – including one or more violent episodes – but was raised in some far away place in quite different circumstances?
But none of that stops people from trying, cooking up all manner of explanations for Elliot Rodger’s killing spree, and in so to doing, executing, broadly, the post hoc, ergo propter hoc fallacy in the process.
These include Heartise (who couldn’t resist blaming the dad despite the clear folly of this as per my earlier posts The Son Becomes The Father and More Behavioral Genetic Facts), who has his own 8-factor causal proclamation. It doesn’t occur to many of these people that Rodger had a special kind of crazy, and that his long diatribe describing his life and his motivations for the killings could have essentially blamed anything, but wouldn’t necessarily nail down the relevant factors for us. Indeed, the serial killer Ted Bundy blamed, among other things, pornography for his killing spree. Are we to believe that these things were more of a factor than the fact he was a murderous psychopath? It’s easy for people to make claims of what motivates their actions – which they themselves might actually believe. But as we see here, the true causes have more to do with the type of person the individual in question is. Elliot Rodger’s fictitious murderous twin brother might have given us a fairly different list of reasons for why he came to the same result.
This little article sums the problem up nicely:
As shots rang out across the courtyard, I ducked behind my desk, my adrenaline pumping. Enraged by the inexplicable violence of this complex and multi-faceted attack, I promised the public I would use this opportunity to push my own pet theory of mass shootings.
Only a few days have passed since this terrible tragedy and I want to start by paying lip service to the need for respectful remembrance and careful evidence-gathering before launching into my half-cocked ideas.
The cause was simple. It was whatever my prejudices suggested would cause a mass shooting and this is being widely ignored by the people who have the power to implement my prejudices as public policy.