New research suggests that genes may be a reason why children are unmotivated at school.

Researchers at Ohio State University collected and analyzed data from more than 13,000 twins from six countries. They found that 40 to 50 percent of the differences in children's motivation to learn could be explained by their genetic inheritance from their parents.

Before the study, researchers thought that twins' shared environment -- such as the family and teachers that they had in common -- would be a larger factor than genetics. Instead, genetics and nonshared environment factors had the largest effect on learning motivation, whereas the shared environment had negligible impact.

"We had pretty consistent findings across these different countries with their different educational systems and different cultures. It was surprising," Stephen Petrill, co-author of the study.

The results strongly suggest that people should think twice before automatically blaming parents, teachers and the children themselves for students who aren't motivated in class.

"The knee-jerk reaction is to say someone is not properly motivating the student, or the child himself is responsible," Petrill said. "We found that there are personality differences that people inherit that have a major impact on motivation. That doesn't mean we don't try to encourage and inspire students, but we have to deal with the reality of why they're different."

The study involved separate studies of twins aged 9 to 16 in the United Kingdom, Canada, Japan, Germany, Russia and the United States. The study methodology and questions in each country were slightly different, but all measured similar concepts.

In all the countries, students completed a measure of how much they enjoyed various academic activities. For example, in Germany, students rated how much they liked reading, writing and spelling. They were also asked to rate their own ability in different subjects in school. For example, in the United States, students were asked to rate how much they agreed with statements like "I know that I will do well in reading next year."

The researchers compared how close the answers were for fraternal twins -- who share half their inherited genes, on average -- with identical twins, who share all of their inherited genes. To the extent that identical twins' answers were more closely matched than those of fraternal twins, that suggests a stronger genetic effect.

The results were strikingly similar across all six countries with children of all ages, Petrill said.

The results don't mean there is a gene for how much children enjoy learning, he said. But the findings suggest a complex process, involving many genes and gene-environment interactions, that help influence children's motivation to learn.

The findings are detailed in the journal Personality and Individual Differences.