A new study by Princeton professors Benjamin Campbell and Samuel Wang probes the biological nature of what people love to learn. They are looking for a link between intellectual discipline, measured by intended academic major, and genetic disorder. Campbell and Wang surveyed 1,077 students from the incoming Princeton freshman class of 2014, asking for intended academic major and a history of familial genetic and mental dysfunction. Of the students that responded, 527 indicated a technical major in the natural sciences, engineering, or mathematics, and 394 indicated non-technical majors in the social sciences or humanities.
The surveys found that students in technical fields were three times as likely as nontechnical students to have a sibling with an Autism Spectrum Disorder, and twice as likely as the national average. Alternatively, humanities students were three times as likely to have a family member who has suffered from substance abuse, major depression, or bipolar disorder. To be sure, Princeton’s student body is uncharacteristically biased towards middle and upper classes, for whom instances of mental disorder are diagnosed at a higher rate than the general population; Princeton students, then, are perhaps more likely to have a sibling with any disorder simply because it is less likely anything would go undiagnosed. Environmental factors could also contribute to the relationship: since siblings spend a lot of time around each other, an intense inclination of one sibling towards a certain mental state—emotional, rational, or anything in between—would naturally influence other members of the family. However, the correlation effect is too large for this to be the only explanation.
For each student, Campbell and Wang created a “predisposition for subject matter” score by calculating the types of mental disorder present in their families. Each sibling with an affective disorder, such as bipolar disorder or depression, was worth one point, and each sibling with an Autism Spectrum Disorder meant a negative point. This resulted in a range of scores, where having siblings who all have autism disorders means the most negative value possible, and having siblings who all have affective disorders the most positive. Using a categorization of intellectual interests that groups students into broad categories of science/technology/engineering/mathematics, social sciences, and the humanities along an axis, each student’s intended academic major could be predicted with incredible accuracy just from information about a variety of familial disorders. Intellectual interest could be forecasted using math so simple it can be done on one hand.
The idea of the tragic, troubled artist has been embedded in our cultural mythos for millennia. Ever since Aristotle declared that “those who have become eminent in philosophy, politics, poetry, and the arts have all had tendencies toward melancholia,” this narrative has persisted. The list goes on: Van Gogh sliced his ear off in a fit of bipolar depression; Virginia Woolf walked into the River Ouse near her home in Sussex, coat pockets weighed down with stone; Kurt Cobain shot himself with a shotgun. Mental disorder runs as a constant through the humanistic canon.
In the sciences there is a similar pattern, albeit of a different nature: whereas previous studies have shown that full-time artists and writers suffer from affective-emotional conditions much more frequently than do control subjects, most cases of dysfunction found in the technical disciplines are Autism Spectrum Disorders. The Autism Spectrum is often used to describe developmental disorders that usually appear in the first three years of life. All the disorders on the spectrum, of which autism and Asperger Syndrome are the most common, are characterized by social deficits and impaired communication. Autism is strongly genetic, but the link between brain and behavior is still up for debate. One of the most popular theories, first proposed by British psychologist Simon Baron-Cohen, is that autism is caused by an imbalance on the Empathizing-Systemizing Scale, which classifies people based on their scores along two axes: strength of interest in empathy and strength of interest in systems. While females generally score higher in empathizing than systemizing and males generally score the reverse, autistic individuals usually fall significantly more on the systemizing end of the scale, no matter the gender. One explanation for the frequency of the trend of autism in the technical disciplines, then, is that a personality inclined towards systemizing would be successful in the sciences, engineering, and mathematics, since they are all highly ordered fields.
What Campbell and Wang’s research suggests is that there is a definite and statistically significant relationship between genes and intellectual interest; since we share on average 50 percent of our genes with our siblings, it is the genetic code that best explains what grants one sibling a mental disorder and another an academic passion. And while it isn’t that surprising that individuals suffering from affective disorders are attracted to the arts—previous studies have found that subjects in a mildly manic state think more fluidly and originally—or that autistic individuals show a greater preference for highly standardized pursuits, it is surprising that siblings who display no symptoms of neuropsychiatric disorder are also drawn to the propensities of their fellow family members. Campbell and Wang hypothesize that this occurrence is probably due to the presence of an inherited phenotype—a displayed trait resulting from the interaction of genes and the environment. The genetic variation between close relatives establishes a continuous scale of the phenotype, with one end yielding only theoretical interest and the other causing dysfunction. The researchers speculate, for example, that there is a phenotype of emotional lability that corresponds to an enthusiasm for the humanities in milder forms and affective disorder in the extreme.
The notion that a person would find interests that made use of and allowed release from their individual conditions seems intuitive. What isn’t explicit is the degree to which the disorder and the discipline are connected. In other words: are our personal passions produced by our proteins? And if they are, does that prove that the sciences and the arts are fundamentally distinct? Recent research has disproved the traditional conception of the humanities and the sciences as belonging to separate hemispheres of the brain; both the right and left hemispheres mostly work in parallel at the level of processes. But this does not mean that there aren’t isolated networks that give rise to distinct pursuits, nor does it delegitimize the fact that we might be programmed to feel more interested in some fields over others. Zooming in to the molecular level might be a more promising way to locate the physical correlates of each skillset, and the code that is responsible for our intellectual dispositions.
Traits, temperament, and interests all begin to develop around the same time early in life, suggesting that they share a sizeable proportion of developmental genes. These findings paint a picture of academic interest as another potentially inheritable trait in the long list of genetic determinants passed down from our parents before us. Our mental pursuits may be predicted by the building blocks of our bodies: we might literally be what we learn.
GREG SEWITZ B’13 forecasted your interests by plugging in your family’s psychopathology.