No matter how hard you study to earn good grades, learning disabilities may be in your genes.

Robert Plomin, professor of behavioral genetics, is researching genetic influence on learning disabilities at the Institute of Psychiatry in London. On Oct. 20 at Penn State, he lectured about a theory that describes how some genes overlap in affecting learning disabilities.

His theory is based on data from the Twins Early Development Study (TEDS), which has been tracking 15,000 pairs of twins in the United Kingdom since they were born between 1994 and 1996. Twins are used because of their similar DNA "to ask whether there are genetic effects in common between these different disabilities," Plomin said in an interview after his lecture.

He is collecting data on twins at age 7 and observing their learning disabilities.

George Vogler, professor of biobehavioral health, who is interested in Plomin's work, said large samples are needed to detect the effects of genes on disabilities because "the effect of any specific gene on a complex trait is likely to be very small."

Stephen Petrill, associate professor of biobehavioral health, who is also familiar with Plomin's research, said the study is important because of the "size of it and inclusiveness of the scope."

"It's an incredible resource," he said.

Plomin is interested in learning disabilities, such as those affecting reading, speaking, writing and math abilities. Although research suggests that disabilities are highly heritable, "proof is somewhat unattainable," Petrill said. "No one has been able to find the actual genes in there that contribute to [learning disabilities]."

Even though genes have yet to be identified for disabilities, Plomin predicts when these genes are found, they will not be specific to one type of learning disability.

For example, if a gene is found for math disability, it may also affect reading disability, he said. It's logical that genes can control many functions because bits of the brain have evolved to work together, Plomin said.

Petrill said, "Those genes overlap with other skills to a greater degree than we thought they did."

If one finds find a gene for one disability, that person may discover a gene that relates to lots of disabilities, he said. In scientific terms, Plomin's research suggests genes tend to be "generalists" rather than "specialists."

What he really wants people to understand is that a disability is not abnormal. There is a normal scale of ability, and on that scale is variation. In turn, people with a disability are still on this normal scale, just on the low end.

Genes aren't the only factor determining learning disabilities; environment plays a role as well. Plomin is trying to make people aware that the environment and genes contribute to learning disabilities, not just one or the other, Petrill said. "Every disorder has its own genes and environment," he said.

Other researchers have examined the overlap of genetic influences on numerous behavior problems. Specifically, a research group in Colorado has shown a genetic relationship between reading disability and attention deficit/hyperactivity disorder.