Yoshio Oro, a retired college professor, believes he has verified his own theory — the more you use your brain, the smarter you get.

Oro was conferred a Ph.D. in social gerontology, the study of society and aging, at Trinity College Dublin in Ireland in April at the age of 81.

"I love starting new things from scratch," he said in an interview during a brief return home to Japan in late May. "People can rejuvenate themselves if they continue to act with something worth living for."