Everybody has regrets. And nobody knows that better than Dr. Amy Summerville.

Not because she has regrets, but because she studies them.

In the "Regret Lab," the name given to the research group studying the phenomenon, Miami psychologists -- led by Dr. Summerville, a University of Illinois-Champaign Urbana graduate, but also -- examine the causes and effects of regret.

More specifically, they study counterfactual thoughts.

"My research is about what's known as 'counterfactual thinking,' which are these thoughts about what might have been, and about regret, which is the emotion based on counterfactual thoughts," Summerville said.

The effects of properly understanding counterfactual thinking are far-reaching. When people generate counterfactuals, they are better at making 'future intentions.' Put simply, they are less likely to make the same mistake.

For instance, if a student who fails an exam thinks counterfactually ("if I had studied, I would've gotten a better score") they are more likely to study in the future. They're also more likely to do other productive tasks relating to their academic performance -- e.g., do more homework, visit office hours or other things that will prevent them from failing another test.

"Because regret is based on these counterfactuals, it ends up being this really useful emotion, as well as obviously being unpleasant as a negative emotion."

The Regret Lab is currently working on a grant from the National Science Foundation studying how using counterfactual thinking could help students in pre-engineering classes to achieve higher scores on exams.

"We are hoping that by helping students think about how they might have done something differently on the first exam, they'll be able to improve course performance and be more likely to successfully complete these courses," Summerville said.

Summerville's research is widely acknowledged, too. In the Wikipedia entry for counterfactual thinking, the section for "current research" cites two major recent publications. She co-authored one of them. Her papers have also been cited over 300 times, according to the Thomson Reuters Web of Science, which is used as an indicator of how impactful a researcher's work is in the scientific community.

Another facet to studying regret is the surface causes -- what things do people regret? Two of Summerville's colleagues, Neal Roese from the Kellogg School of Management and Mike Morrison from the University of Illinois, conducted a large-scale telephone survey to find out.

The answer: romance.

In 2011, the researchers determined about 18 percent of Americans most regretted a romantic decision. Following that were family, education and career choices. In 2012, they went further, delving into the implications of vocational and social regrets.

Social relationships, including romantic failures, broken friendships and lost time with family are together the "most pivotal component of life regrets," Roese, Morrison and Kai Epstude at the University of Groningen write.

"I find the ways that people learn from their mistakes to be really interesting. We all have negative experiences in life," Summerville said. "I think that understanding the ways we use that to become better is really interesting."