Twin Studies

I note that Cal State Fullerton Psychology Professor Nancy L. Segal has a new book out on twins separated at birth or in early childhood, entitled Born Together, Reared Apart. I have not yet been able to get this book through my university library or local public library, but I’ve put in requests for this latest contribution by an important researcher on the genetic influences on human character and behavior.

 The historical origins of twin studies lie in the work of Sir Francis Galton, a cousin of Charles Darwin,  an early pioneer in the study of genetics, and a founder of the controversial theory of eugenics. Galton conducted some of the earliest systematic studies of human twins in the 1870's. He recognized the difficulty of identifying the extent to which human traits are biologically inherited and the extent to which traits are produced by diet, upbringing, education, and other environmental influences. Borrowing a phrase from William Shakespeare, Galton called this the "nature versus nurture" problem, a phrase that has become standard in the social sciences. Galton reasoned that he could attempt to find an answer to this problem by comparing similarities among people who obviously shared a great deal of biological inheritance with each other with similarities among people sharing less biological inheritance. Twins offered the clearest example of people who shared common biological backgrounds.

Galton contacted all of the twins he knew and he asked them to supply him with names of other twins. He obtained 94 sets of twins. Of these, 35 were sets of twins who were very similar, people that we would today call identical twins. These 35 pairs reported that people often had difficulty telling them apart and 9 pairs were so close to one another in appearance that the 18 individuals reported having mistaken their own images in mirrors with their twins.

Using questionnaires and interviews, Galton compared the 35 identical pairs with the other twins. He found that the identical twins were much more similar to one another in habits, interests, and personalities, as well as in appearance. They were even much more alike in physical health and in susceptibility to illness. The one area in which all individuals seemed to differ markedly was in handwriting.

Since Galton's time, researchers have learned how biological inheritance occurs and this has made possible an understanding of why twins are similar. It has also enabled researchers to make more sophisticated use of twins in studies that address various aspects of the "nature versus nurture" problem. Parents pass their physical traits to their children by means of genes in chromosomes. Each chromosome carries two genes for every hereditary trait. One gene comes from the father and one comes from the mother.

Any set of full brothers and sisters will have a good deal of heredity in common, since all of their genes come from the same parents. However, brothers and sisters usually also differ substantially. The cell that develops into a living creature, the zygote, is created when the ovum, or egg, is fertilized by the sperm. Each zygote will combine genes from the father and from the mother in a unique combination, so different zygotes will develop into quite different people. Even when two fertilized eggs are present at the same time, as in the case of dizygotic or fraternal twins, the two will be different combinations of genes from the mother and the father.

Identical twins are an exception to the rule of unique combinations of genes. Identical twins develop from a single zygote, a cell created by one union of egg and sperm. Therefore, monozygotic twins, twins from one zygote, will normally have the same genetic make-up. Differences between genetic twins, researchers argue, must therefore be produced by environmental factors following birth.

The ideal way to conduct twin studies is to take the approach of Segal in this new book and compare monozygotic twins who have been reared apart from one another in vastly different types of families. This is rarely possible because the numbers of twins separated at birth and adopted are quite limited. For this reason, researchers in most twin studies use fraternal twins as a comparison group, since the major difference between monozygotic and dizygotic twins is that the former are genetically identical. Statistical similarities among monozygotic twins that are not found among dizygotic twins are therefore believed to be due to genetic inheritance.

One of the main sources for twin studies is the Minnesota Twin Registry. A second major source of twin studies is the Virginia Twin Registry. This is a register of twins constructed from a systematic review of public birth records in the Commonwealth of Virginia. A few other states also maintain records of twins. Some other organizations, such as the American Association of Retired People (AARP) keep records of twins who volunteer to participate and make these records available to researchers.

Although twin studies are one of the best available means for studying genetic influences on human beings, questions about this approach do exist. Twin studies assume that monozygotic twins are biologically identical, but some critics have claimed that there are reasons to question this assumption. Even though these twins tend to show greater uniformity than other people, developmental differences may emerge even in the womb after the splitting of the zygote.

Twins who show a great physical similarity may also be subject to environmental similarities, so that traits believed to be due to genetics may in fact be a result of upbringing. Some parents, for example, even dress twins in matching clothing. Even when twins grow up in separate homes without being in contact with one another, their appearances and mannerisms may evoke the same kinds of responses from others. Physical attractiveness, height, and other characteristics often affect how individuals are treated by others, so that the biologically based resemblances of twins can lead to common experiences. Critics of twin studies point out that twins constitute a special group of people and that it may be difficult to generalize findings from twin studies to the population at large.

Despite the concerns about twin studies, these have provided evidence that a substantial amount of human character and behavior may be genetically determined. In 1976, psychologists John C. Loehlin and Robert C. Nichols published their analyses of the backgrounds and performances of 850 sets of twins who took the 1962 National Merit Scholarship test. Results showed that identical twins showed greater similarities than fraternal twins in abilities, personalities, opinions, and ambitions. A careful examination of backgrounds indicated that these similarities could not be explained by the close treatment received by identical twins during upbringing.

Later twin studies continued to provide evidence that genes shape many areas of human life. Monozygotic twins tend to resemble each other in probabilities of developing mental illnesses, such as schizophrenia and depression, suggesting that these psychological problems are partly genetic in origin. A 1996 study published in the Journal of Personality and Social Psychology used a sample from the Minnesota Twin Registry to establish that identical twins are similar in probabilities of divorce. A 1997 study in the American Journal of Psychiatry indicated that there is even a great resemblence between twins in intensity of religious faith. Twin studies have offered evidence that homosexual or heterosexual orientation may be partly a genetic matter.

For my own part, I’ve concluded that much of the variation among individual human beings can be attributed to genetic predispositions, and I see the study of separated twins as the best evidence for this conclusion, which is why I’m eager to obtain Dr. Segal’s new book. Beyond this, though, I’m curious about several other “nature versus nurture” (or “nature interacting with nurture”) questions. One of those concerns just what genetic identity means among highly adaptable human beings. The same individual will react in dramatically different ways to different circumstances, so one of the meanings of “socialization” could be how genetically shaped personalities respond to varying social environments.

One of the biggest issues, opening great possibilities for controversy, is whether significant genetic variation exists at the aggregate or categorical levels, as well as at the individual level. Even twins separated early in life generally grow up within the same cultural and national settings. Even if we could find individual sets of twins reared in different countries or within different racial or ethnic groups, we would not have a large enough number to draw conclusions about the extent to which variations at group levels result from genetic predispositions, shared historical legacies, or environmental influences.

Review of Soul Dust by Nicholas Humphrey

Daniel C. Dennett’s 1991 book Consciousness Explained has often been jokingly re-titled “Consciousness Explained Away,” since the book attempts to account for all mental phenomena in neurological terms and to discard the Cartesian subject as an illusion. Nicholas Humphrey’s Soul Dust: The Magic of Consciousness shares Dennett’s fundamental perspective on consciousness, although Humphrey’s poetic style also manages to communicate its author’s joy in the supposed illusion. Humphrey argues that consciousness, understood as the sense of self-awareness in experience, is essentially an echo created by continuous feedback cycles in the brain. The perception of a self, the observer of one’s sensations and actions, is ultimately only a sensory feedback loop.

Humphrey attributes this illusory theater of self to evolution. Creatures that enjoy existing have a greater commitment to continuing existence than those driven by mere instinct to live. Consciousness, then, is evolution’s way of intensifying the attachment to life. Human beings, with the most highly developed feedback loops, are “connoisseurs of consciousness,” as Humphrey describes us, who take the most intense pleasures in their perceptions. The author supports this claim by drawing on his impressive knowledge of literature, as well as philosophy and the social and physical sciences.

Although I found the book interesting, I remain unconvinced by its claims. On the subject of consciousness, I think I will have to list myself among those that Colin McGinn has described as “mysterians,” who believe that the ultimate nature of the phenomenon will always remain mysterious and cannot be solved (or explained away).  Most broadly, this is because I do not think that one can completely account for any system from inside of that system. Unable to move outside the boundaries of our own minds (at least in scientific terms), we can never trace the circumference of mind.

On the issue of consciousness as a feedback loop, I have two major concerns. The first and lesser one is that Humphrey’s description of how the loop supposedly works is highly abstract and schematic. He does not provide enough of an account of how this might happen as a matter of neurological connections within the brain. The second and greater concern is that I do not see that we can move from analyzing how something works (assuming we could) to saying what it is.

To say that consciousness is an “illusion,” moreover, strikes me as deeply problematic. There can only be an illusion if there is someone to perceive something incorrectly. The magician’s illusion depends on the presence of an audience that can be misled. But Humphrey, like Dennett, argues that the audience itself is an illusion in the Cartesian theater.

Finally, I remain skeptical of the evolutionary argument about the survival value of the pleasures of consciousness. Kierkegaard identified human consciousness with the sense of dread and a great deal of human awareness is not much fun. To the best of my knowledge, human beings are the only creatures who kill themselves out of existential despair. I can’t see much evolutionary survival value in that.

Humphrey does give some attention to anxiety, but largely writes it off as a side effect. His quotations of poetry and literary reflections, though, suggest that the view of humans as “connoisseurs of consciousness” might seem plausible to those of us in the enviable situation of modern middle class intellectuals, but it also might seem like a strange claim to many of our forebears in the long tragedy of history.

Schools as Activist Training Centers

In today’s email, I received an advertisement from Harvard University Press for their new titles in education. Among these is Meira Levinson’s No Citizen Left Behind. On first glance, this book’s advocacy of “civic education” seems to be a call for a renewed emphasis on the subject traditionally known as “civics.” The misleading blurb from the Library Journal tells us that “Levinson advocates restoring civic education.” But a closer look at the book description makes it clear that she doesn’t want to “restore” any part of the schooling of American citizens. Instead, she wants to turn public schools into centers for training activist cadres.

According to the book summary, “No Citizen Left Behind argues that students must be taught how to upend and reshape power relationships directly, through political and civic action  ... Schools should teach collective action, openly discuss the racialized dimensions of citizenship, and provoke students by engaging their passions against contemporary injustices. Students must also have frequent opportunities to take civic and political action, including within the school itself.” 

I do not question Dr. Levinson’s right to go about “upending power relationships” or to define “injustice” as she chooses or to engage in legal “collective action” with those who see things as she does. But I can think of few things more fundamentally contradictory to a free society than using the public schools to institutionalize the organization of an ideological program. That, however, is exactly what the “civic education” movement is all about.  

Drugs and Credentialization

About a decade ago, a group of students in my research methods class designed a study of drug use at our university. They were not able to take a representative sample of undergraduates in the anonymous survey, but the results of their project did indicate that use was common. This did not surprise me, but I was interested to find that the most popular substances and the motivations for consuming them were different from what I, having been an undergraduate in the early 70s, would have expected. The most frequently used substance was a stimulant known as Adderall, prescribed for attention-deficit disorders. About one-third of those surveyed reported having taken this medication, and only a tiny number said they had taken it for its official purpose. Most of the survey respondents said they had used Adderall as a study drug, because it increased their concentration and enabled them to finish academic projects at the last minute. I did not ask my students if any of them had worked on the project under the influence.

I see in today’s The New York Times that the long-standing college drug of choice has become standard among highly competitive high school students. Allan Schwarz reports that secondary school students seeking an edge on the SATs or on improving the records for admission to elite, selective colleges now routinely turn to Adderall and related substances to push their scores up. Schwarz compares “study drugs” to the substances athletes sometimes use to get an advantage on the competition.

While there is some evidence that stimulants can help boost test scores, there is no suggestion that these can actually contribute to depth of understanding or to long-term educational goals. The dope is all about Grade Point Averages, SAT scores, and getting the right credentials from the right places.  To understand why education has turned into an arms race of medications, we need to think about what has happened with higher education in our nation.

On the eve of World War II, fewer than 5 percent of Americans over age 25 held college degrees. Today, that percentage has gone up to about one-third. Over this period, we have increasingly defined college as the route to upward mobility and many Americans, especially in government and academia, have come to expect that everyone should be upwardly mobile and that the best way to promote this goal is by extending higher education to as many people as possible. One of the difficulties with this effort is that the occupations that really require higher education have not kept pace with the numbers of graduates we have been cranking out of our institutions. During the 1970s, for example the percentage of people in the labor market with college degrees passed the percentage in professional and technical fields, and the gap between the two has grown wider ever since.

As college became the gateway to the supposed good life for more people, just getting the credentials became more important than any of the skills or knowledge those credentials might represent, leading students to focus ever more on the test scores and GPAs, in the process creating pressure for grade inflation and drawing attention from educational content. Through readily available loans, college administrators and government policy makers attempted to subsidize everyone’s mobility, even though opportunities were increasing only in a limited number of technical fields.  This flooded the market, so that the college diploma began to turn into an entry-level credential. In order to achieve distinction in a world in which degrees were everywhere, and obtaining a distinctive degree was widely identified as the main route to prosperity, young people came to see getting into an elite college as they way to stand out from the herd. Ironically, spreading educational opportunity more widely has only ratcheted up the competition to get ahead.

Adderall and the other test performance enhancing drugs are weapons in this intense struggle for the right kinds of credentials.

Percentages of Americans in the Labor Market with College Degrees and Percentages in Professional and Technical Occupations, 1940 to 2006-2008

Source:  Ruggles, S., Sobek, M. Alexander, T., Fitch, C. A., Goeken, R., Kelly Hall, P., King, M., & Ronnander, C. (2004)  Integrated Public Use Microdata Series: Version 3.0 [Machine-readable database]. Minneapolis, MN: Minnesota Population Center [producer and distributor].

Remembering the Penitentes

         
           









 Anonymity covers them with grace
 as dancers define grace, reduction to form,
 curved lines throwing boundaries in space
that slip away with the motion of an arm.
           
They walk in file, bare backs and hooded heads
inverting normal patterns of disclosure.
Slow steps on earth, in air the knotted threads
move together in repeated measure.

The procession winds the streets. The line
 twists as it turns like their whips, magnified.
The lashes leave trails of blood along their spines,
 and along the spine of the street they leave behind.

Everything is changed. Sins become pain,
the spirit descends on the body, flesh ascends
to prayer, display provides release from shame,
offense turned inward offers up amends.

The sliding doors of the stores where the men drank
and swapped gossip yesterday are locked.
The fishing nets are folded on the bank
 at the edge of town where the outriggers are docked.
                     
The coconut trees are undisturbed by wind:
all struggle in this scene is gathered in
these bodies and released from broken skin.                                                                  
   

Campus Civility Campaigns

The Foundation for Individual Rights in Education (FIRE) discusses the spread of “civility programs” among American colleges and universities, mentioning a passage from my own university’s Code of Student Conduct.  In defense of Tulane, I’d say that our civility requirement is merely fatuous, expressing an expectation that students will “speak and act with scrupulous respect for the human dignity of others.” I don’t know how anyone could tell whether or not a student’s respect is “scrupulous,” but the vagueness of the injunction would, I hope, make violations difficult to identify and enforce. By contrast, Harvard actually asks students to sign a “kindness pledge” promising to “sustain a community characterized by inclusiveness and civility,” and reportedly posts the names of those who have and have not signed in the entryways of residence halls.  Former Harvard Dean Harry Lewis denounces this as “public shaming.”  

What’s wrong with college civility campaigns? I’m in favor of politeness and I think that learning that ad hominem arguments are fallacious is a legitimate part of an education. But moral crusades to get students to watch what they say can also further narrow the rigidly conformist intellectual culture of modern universities. And precisely because that culture is so conformist today, accusations of “incivility” and failure to be “inclusive” will inevitably be leveled mainly against those who disagree with prevailing assumptions.

Wesleyan Faces Reality

Wesleyan University has realized a basic fact of life. Someone must pay for all goods and services, including educational goods and services. Either the one who receives them pays or someone else pays on the recipient’s behalf. If the recipient does not have the funds, and cannot be realistically expected to come up with sufficient future funds to justify provision on credit, and no one else is willing or able to cover the costs,  then the goods and services just can’t be made available.

I am referring to Wesleyan President Michael Roth’s declaration that the university will no longer pursue a “need-blind” admissions policy for potential students.  Until now, an article in Inside Higher Education tells us, Wesleyan has been one of the few universities that both admit students without regard to need and promise to meet the full financial needs of all those admitted. This was clearly unrealistic, and I expect that the other institutions that offer this kind of guarantee will follow Wesleyan’s example.

Even colleges that do not follow the need-blind guarantee would do well to limit financial aid, while concentrating efforts on bringing costs down for all students. These two are related because need-based scholarships shift costs to other tuition payers, pushing up sticker prices, while loans to students pump up college price through long-term burdens on borrowers or taxpayers.

One of the more inane remarks on need blind admissions, quoted in the article, came from Ronald G. Ehrenberg, a professor of industrial and labor relations and economics at Cornell University, director of the Cornell Higher Education Research Institute, and member of the Board of Trustees for the State University of New York. “If higher education is supposed to be a vehicle for social mobility, and the purpose is to train the next generation of leaders, and we believe that leaders should come from all spectrums of social class, then there’s a strong argument to [maintain need-blind admissions].”  One has to wonder how Dr. Ehrenburg could imagine that there are enough places at the top of our economy and society so the vast numbers of graduates we have been cranking out of our colleges can acheive "upward mobility" or where the “generation of leaders” produced by debt and vast tuition subsidies will find their followers.