RIO DE JANEIRO (AP) — After fulfilling her goal of medaling in five straight Olympics, Britain's most decorated female athlete isn't quite sure what comes next.

But don't be surprised if Katherine Grainger's next endeavor involves studying serial killers and other brutal criminals.

"It's quite a dark subject matter," the 40-year-old Scottish rower told The Associated Press on Thursday after winning silver in the women's sculls with Victoria Thornley. "It's looking at the human experience quite at the limit. You look at very extreme personalities and extreme behavior."

Over the past two decades Grainger has managed to combine advanced academic studies with a career in competitive rowing. Before Rio de Janeiro, she had won silver medals in Sydney, Athens and Beijing and gold in London. No other British woman has five Olympic medals.

Grainger has a law degree from the University of Edinburgh and took a timeout from rowing after the 2012 Olympics to finish her Ph.D. at King's College in London.

"I was studying the concept of life meaning life as a sentence. That looks at the worst of the worst criminals in the view of the law," she said.

Once that was out of the way she returned to rowing, but just barely made the British team for Rio. Grainger said she hasn't decided on her future yet but doubts she'll be back for a sixth Olympics in Tokyo in 2020.

"I'd be very surprised if it goes beyond this point," Grainger said. "I'm happy, I'm content, I'm thrilled, and I can walk away into the sunset and let other people have this dream."

She and Thornley, who is 12 years younger, were in gold-medal position until the final stretch of Thursday's race. They were beaten by Magdalena Fularczyk-Kozlowska and Natalia Madaj of Poland.

"We just ran out a little bit right at the end there. But I'm so proud. I would far rather we do that and not quite make it than never put ourselves in that position," Grainger said. "I really, really did not want to leave my fifth Olympic Games without a fifth Olympic medal."

In other rowing races, New Zealand's Eric Murray and Hamish Bond successfully defended their Olympic gold in the men's pair, drifting away from the other crews after the first 500 meters. The Kiwis remain undefeated in the event, with 69 wins since 2009.

Brothers Martin and Valent Sinkovic overtook a Lithuanian crew in the final stretch to win Croatia's first ever rowing gold medal. German crews won both the women's and men's quadruple sculls, while Switzerland won the gold in the lightweight men's four.