Psychologists have long known that people confident in their ability to control their destinies are more likely to adjust well to growing old than those who feel that they drift on the currents of fate.

　　Two researchers who questioned hundreds of Swedish twins report that such confidence, or lark of it, is partly genetic and partly drawn from experience.

　　They also found that the belief in blind luck-a conviction that coincidence plays a big role in life is something learned in life and has nothing to do with heredity.

　　The research was conducted at the Karolinska Institute-better known as the body that annually awards the Nobel Prize for medicine by Nancy Pedersen of the Institute and Margaret Gatz, a professor of psychology at the University of Southern California in Los Angeles. Their results were recently published in the United States in the Journal of Gerontology.

　　People who are confident of their ability to control their lives have an "internal locus of control,"and have a better chance of being well adjusted in their old age, said Pedersen.

　　An "external locus of control," believing that outside forces determine the course of life, has been linked to depression in latter years, she said.

　　"We are trying to understand what makes people different. What makes some people age gracefully and others have a more difficult time?" she said.

　　The study showed that while people have an inborn predilection toward independence and self-confidence, about 70 percent of this personality trait is affected by a person's environment and lifetime experiences.

　　Pedersen's studies, with various collaborators, probe the aging process by comparing sets of twins, both identical and fraternal, many of whom were separated at an early age.

　　The subjects were drawn from a roster first compiled about 30 years ago registering all twins born in Sweden since 1886. The complete list, which was extended in 1971, has 95,000 sets of twins.