Sorry, Superman. You’re probably overdressed.

The man of steel’s cape doesn’t make him a superhero. What transforms him into one beat in his bulletproof chest — an altruistic heart. And now, scientists have proved it.

A study by a University of Florida Health endocrinologist and collaborators in Ireland and Arkansas analyzed the 25 top-grossing superhero movies and concluded that just 16% of superheroes wore capes. A far more common trait is altruism, found in 97% of the superheroes, the paper concluded.

“The study clearly demonstrates that having an altruistic mission is the key defining feature to making someone a superhero, be they Superman, a medical professional, a first-responder or a teacher,” the study noted. Lex Luther need not apply.

Lest anyone think this scientific study is no more authentic than Captain America’s “vibranium” shield, the analysis is very real, right down to its citations, design and statistical analysis. Its authors’ purpose is to use it to teach medical trainees and others how studies are built, but in a translatable way.

The peer-reviewed study was published Sept. 19 in the Irish Journal of Medical Science.

The researchers did the work after hours because they didn’t want their day jobs disrupted by superhero analysis. The study also required no funding.

“As physician-scientists, we often need to explain complex research methods to people who may not be familiar with a study’s language,” said UF Health endocrinologist Dr. Naykky Singh Ospina, the study’s lead author. “Here, we try to get them engaged in a way that’s accessible and enjoyable.”

Singh Ospina added, “The study methodology is actually very rigorous.”

In fact, she and the study’s senior author, endocrinologist Dr. Derek T. O’Keeffe, of the University of Galway in Ireland, independently watched every minute of all 25 movies in about two months.

The team set research protocols, decided what traits to look for in superheroes, calculated sample size and did all the things scientists do to examine and test a question.

In this case, researchers examined the catchphrase, “Not all superheroes wear capes,” a saying popularized during the COVID-19 pandemic, often used to describe medical workers. Is it true?

O’Keeffe, Singh Ospina and University of Arkansas endocrinologist and co-author Spyridoula Maraka are friends who did their fellowship training together at the Mayo Clinic in Rochester. A Galway statistician, Andrew Simpkin, also joined, crunching numbers like the Hulk crunches cars.

“The Physicians did the heroic work of watching the movies, while the Statistician did the villainous calculations,” the study said.

Singh Ospina is a superhero film enthusiast, like her co-authors. In fact, she had already seen most of the movies on the list, which is heavy with Spider-Man and Avengers flicks. Iron Man 3, Captain Marvel and Aquaman, among others, also made the cut.

“But for this, I watched them from a different angle,” Singh Ospina said. “I searched for our variables of interest in front of my TV with some popcorn and snacks and a spreadsheet file.”

She and O’Keeffe had a preselected list of possible superhero attributes, including whether the hero is human or alien, their intelligence, whether they have an alter ego (think Clark Kent) and, of course, altruism and a cape. They also examined villains, who sometimes enjoy capes, absent the altruism.

The study noted that being a superhero is difficult and carries much responsibility that, in professions like medicine, can lead to burnout. Great expectations are put on a superhero’s shoulders.

“Policymakers should be cognizant of this,” it said.

In the end, the researchers’ findings were as clear as a crystal of Kryptonite.

“Capes may look dramatic, but it’s altruism that truly defines a superhero,” O’Keeffe said.

Singh Ospina, an associate professor in the UF College of Medicine’s division of endocrinology, diabetes and metabolism, said watching so many superhero movies hasn’t ruined the genre for her.

“You cannot ruin superhero movies,” she said. “For me, that can never happen, ever.”

The researchers remained objective and avoided identifying with their study subjects.

“No authors,” the paper reassured, “wore capes during the production of this paper.”