Researchers prepare for the fifth phase of the study in the lab of USC professor Laura Baker.
For the past 11 years, hundreds of sets of twins have visited the lab of Laura Baker, professor of psychology at the USC Dornsife College of Letters, Arts and Sciences, to participate in a study focusing on the roles heredity and environment play in producing delinquent behaviors in paternal and identical twins.
So far the findings have been remarkable. According to Baker, for the first time data showed that psychopathy – a syndrome involving callous and unemotional traits combined with antisocial, manipulative and deceitful behavior – has been found consistently across childhood and adolescence and that genetics may play a large role in this condition.
“We see a strong genetic component to antisocial traits in children as early as 9 to 10 years of age,” Baker said. “There is a fairly stable set of traits both phenotypically and genetically across development. It does look like there may be some of the same biological signatures associated with these traits that we’ve seen in adulthood that appear as early as childhood and adolescence.”
Baker’s research looks at environmental versus genetic disposition in delinquent behavior. Researchers in Baker’s laboratory are examining biological and social factors that cause antisocial outcomes.
“If we understand the nature of these traits more clearly and understand their roots in childhood, then we are in a better position to come up with early identification, interventions and prevention of delinquent behavior,” said Baker, director of the Southern California Twin Project based at USC Dornsife.
To gain a better understanding of how genes and environment influence relationships, Baker and her team are comparing and contrasting behaviors of monozygotic (identical) and dizygotic (fraternal) twins.
For example, the researchers are observing the types of friends selected by twins. If identical twins choose the same kinds of friends more often than paternal twins, then a genetic influence toward selecting preferred peer characteristics may be at work. The relationship between deviant peers and a child’s antisocial behavior may not reflect a simple directional cause from peers to the child. Instead, there are likely to be complex, multidirectional influences whereby children choose certain kinds of peers, who in turn enhance their antisocial tendencies.
The Twin Project, funded through 2014 by the National Institute of Mental Health (NIMH), has been tracking 750 sets of twins from socioeconomically and ethnically diverse backgrounds since they were 9. The participants will either be 19 or 20 when they return to participate in the fifth phase of the study. Wave five assessments will take two to three years to complete.
Then the twins will participate in a test similar to one they underwent at the study’s onset. During the six- to eight-hour tests conducted in the Mudd building, their parents were interviewed about their children’s behavior by a USC Dornsife undergraduate, graduate student or postdoctoral researcher. Each twin was interviewed separately by a member of Baker’s team about his or her sibling before beginning their psychophysiology tests.
Seated in a chair opposite a computer monitor, a research assistant placed a 32-electrode cap on the twin participant’s head – a stretchy mesh headpiece akin to a swim cap but with electrodes attached to each end of the wires.
Each twin was given eight to 10 tasks meant to elicit some stress, such as making quick decisions, or to evoke emotional responses while viewing scary or sad movie clips or pictures of angry faces. All the while, heartbeat, breathing, sweating, eye blinks and electroencephalogram readings were collected to determine how each twin physically responded to specific conditions.
Observations of heart rate, breathing and eye blinks provided researchers with insight into how each child responded toward stimuli. Using this data, researchers have discovered that more aggressive antisocial children displayed low-resting heart rates and low arousal, as well as dampened responses to incoming information from the environment.
Project manager Karina Gómez has been involved in the study since its launch in 2001. After graduating with a bachelor’s in communications and a minor in psychology from USC Dornsife in 2001, she returned to Baker’s lab as a staff member.
“This study is tapping into something that can be taken out of the research realm and put into practical use,” Gómez said. “It has a lot of implications for education and for understanding learning disabilities and problem behaviors in children and adolescents.”
Baker’s lab also has found that the lower heart rate in aggressive antisocial children almost is entirely caused by genetics. Baker emphasized, however, that the findings so far do not signify that biology is destiny.
“It is more a biological risk that seems to be inherited,” said Baker, who joined USC Dornsife in 1984. “There is always opportunity for the environment to modify things.”
The study’s findings will serve as a foundation for developing interventions and preventions.
With the wealth of information emerging from the study, Baker can foresee following the twins throughout adulthood. The data has drawn great interest from undergraduate and graduate students.
Baker carefully selects those who join her team of interviewers, assessors and psychophysiology testers. So far, more than 150 undergraduate students have volunteered in her lab.
“Many of them have become wonderful key members,” said Baker, who added that 25 to 30 researchers are working in the lab during peak times of data collection.
The opportunity to learn how the body responds to various events and stressors led Tiffany Pouldar, a senior psychology major, to Baker’s lab.
“In Dr. Baker’s lab, I get experience in both psychology and health field applications,” said Pouldar, an aspiring physician. “I’m not just reading something out of a book but seeing it with my own eyes and applying everything I have learned in the lab.”