SAN DIEGO -- Scientists at the University of California, San Diego are trying to unlock the answer to successful aging by testing the brains of twins.

Sets of twins from all parts of the country are coming to San Diego to help unchain the mysteries of their genetically similar minds.

The secrets to successful aging could be locked in the human brain.

Experts said human genes are responsible for about half our memory. It is believed the other half might be shaped by environment and behavior.

"I think genetics is really what controls because I have a lot of the same faults and do the same things," said twin study participant Ron Rowe.

Rowe’s brother, Don, added, “You find that the older you get, the less you remember, for sure.”

The Rowe twins have traveled from Louisville, Ky., to take park in the twin study of aging at UCSD.

"We compare identical twins who share 100 percent of their genes; they are genetically identical to fraternal twins, who share only about 50 percent of their genes," said UCSD twin study researcher Dr. Bill Kremen.

This unique mathematical relationship helps researchers figure out how many different traits are influenced by genes and by the environment.

Kremen said, “It's a way to answer the age-old question, ‘Is it nature, or is it nurture?’”

The Rowe twins are put through a battery of tests that will challenge their minds.

In one test, Ron must say the color of ink even though the typed word says a different color. It is a tough task for the brain.

"What we are doing is comparing how much did they slow down when they are having to say the colors because it requires them to inhibit this automatic tendency to say the word," said Kremen.

Genetics definitely seem to play a huge role in the Rowe twins’ thinking.

Recently, they both picked out new bedroom furniture.

"I picked ours out and he picked theirs out, and we picked the same identical bedroom set and had never even talked to each other about it," said Don.

The genetic bond is still going strong.

"We are going to be 60 our next birthdays, so we both still get around good. So, I don't think we are doing too bad,” said Ron.

Researchers said memory and brain function help our quality of life, and they said they hope to find predictors of those things to help people age more successfully.

So far, about 500 twin pairs have been tested in three basic areas -- cognition, personality and health.