On his office computer, UCSD professor Anders Dale is playing a film: a time-lapse picture of a year in the life of a young monkey’s brain. As the monkey’s brain grows, the image expands and changes shape like a monochrome flower unfolding.

“You can see the changes here,” Dale says, pointing to an area in the image that’s swelling rapidly. “This is the kind of thing we want to look at in the kids.”

Dale, together with colleagues at Scripps Genomics and UCSD’s Center for Human Development, is embarking on an ambitious two-year effort to probe the genetics of brain structure, personality and mental ability.

The researchers plan to scan the brains of 1,400 children from 3 to 20 years old, collect DNA samples from each and test attributes like memory and attention span. The UCSD team will then assemble this information into a database available to other scientists and look for links between brain structure, personality and genetics.

Its lead investigators see it as a starting point for a larger program with far-reaching goals. They hope that if they can identify some of the genes involved, their data could find uses in treating mental illness and improving education to better match needs for individual children.

The UCSD research project is part of a broader effort to understand how genes shape what we become. They’re tackling the ultimate question for geneticists: What makes us who we are?

Past studies of twins have tried to pin down which differences between individuals are attributable to genes and which stem from upbringing or experience. But the genetics of many complex traits remains largely unknown.

Genetically, all humans are far more alike than we are different. The human genome is a chemical code more than 3 billion letters in length, written into a spiral ladder-shaped molecule called DNA. It’s estimated that the sequence of these letters in the genomes of any two individuals, from Jerry Sanders to Albert Einstein, is more than 99 percent identical.

But the human genome is so large that even the small fraction differing from one person to the next amounts to millions of variations. These inherited variations account for many of the differences between people. The extent to which they decide traits like intelligence or risk-taking, however, is an old and thorny controversy.

The Difference Between a Serial Killer and a Saint

Clearly both genes and environment — nature and nurture — each play a part in deciding the differences between a genius and a dunce, a serial killer and a saint. But determining how genes and environment interact to mold our likes and dislikes, our loves and hates is a complex puzzle with far-reaching ramifications.

Scientists have tried answering those questions before, in studies that sampled the DNA from thousands of people and looked for correlations between genes and traits or diseases. But the results have often been disappointing.

Studies of height, for example, found dozens of genes taken together accounting for only a fraction of the variation in how tall people become. It’s very likely that most complex human traits are controlled by interactions between large numbers of genes, like an orchestra of instruments that together sound a single melody.

Several studies have found that differences in brain structure seem to be closely linked to genetics and that brain structure may also be linked to certain traits like IQ. Since brain architecture is more closely controlled by genes, identifying the genes involved is one way to start the search for the genetic basis of personality traits.

By compiling brain scans, DNA samples and personality tests into a single database, UCSD’s project could offer researchers a more powerful approach and a broad range of data not readily available before. And this project will focus on normal brain development, unlike some of the past attempts aimed primarily at understanding disease.

But the staggering complexity of genetics and personality will make any effort to illuminate the links between the two a formidable task.

Clarifying the Origins of Mental Disorders

Assuming researchers can decipher the genetics of personality, this information could find numerous uses — in treating disorders like schizophrenia or autism, for example. The genetic factors that may play a role in schizophrenia and autism are still poorly understood. Understanding the genetics of normal brain development could give researchers ways to spot abnormalities and find targets for treatments.

Laura Baker, a University of Southern California psychologist who studies how genes and environment influence behavior, sees another benefit.

“There’s often a very blurred line between what’s considered normal and abnormal behavior,” she says, “so there’s always the question — are [some] mental illnesses extremes of normal behavior?”

Clarifying the origins of mental disorders could help predict who is vulnerable and how to safeguard them.

It’s also possible that certain genetic profiles place people at increased risk for conditions like depression or addiction, like landmines hidden in the genome waiting for the right conditions to trigger them. “Maybe some people are going to be more likely to develop [post-traumatic stress disorder] if they go into the service,” says Terry Jernigan, director of UCSD’s Center for Human Development and the lead investigator for the study. “Having that information could help them avoid risky situations.”

But for Jernigan, the single most interesting application might lie in the classroom. Understanding how genes contribute to personality, Jernigan believes, could help settle some important questions, such as whether an optimal teaching style suits all children, or whether different personalities respond best to different methods depending on their genetic makeup.

“Does genetic variation matter? And if it does, how does it matter? And without the actual scientific data, we’ll argue this in circles forever,” Jernigan says.

While the UCSD-led project is unique in some of its aims, it’s not the only study trying to answer some of these questions. The National Children’s Study, a large-scale national effort, will track 100,000 children from before birth (in some cases even before conception) to age 21 to figure out how the environment around them impacts their health and development. UCSD is one of the participating centers.

How successful the new UCSD effort will prove remains to be seen. Jernigan emphasizes that given the bewildering diversity of human behavior, “this project by itself will leave many, many questions unanswered.” But methods like these, despite their inherent limitations, may offer the best shot yet at solving the mystery of what makes each personality unique.

Please contact Jonathan Parkinson directly at jlparkinson1@gmail.com.

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