All the songs that tell people to listen to their hearts may be truer than crooners realize, a new study says.

Test subjects who were more conscious of their heart rates were more likely to "trust their guts" when making decisions—and in some cases that intuition paid off.

University of Cambridge researcher Barnaby Dunn and colleagues had 28 subjects play a virtual card game in which they could win money by choosing cards from four supposedly random decks. The game involved guessing whether a chosen card would be the same color as an already upturned card.

In actuality the decks were stacked, and it was only possible to win big by choosing from two of the four decks.

No matter what the participants guessed, they would be correct 60 percent of the time if they chose from deck A or B. They'd be right only 40 percent of the time if they chose from deck C or D.

"In the card game, there were good choices to make and bad choices, and when they make bad choices, their body should give them an arousal signal," such as an increased heart rate, Dunn said.

Gut Instincts Can Be Mixed Blessing

Previous work done by University of Iowa researchers had shown that subjects playing a similarly stacked card game began avoiding the "bad" decks long before they were aware of it, about the same time that their palms began to sweat.

In the new experiment, the researchers first asked people to count their own heartbeats. "We don't want them to feel their pulse [with their fingers], and we ask them to take their watches off" for the heartbeat-counting exercise, Dunn said.

"Most people say, I've got no idea [what my heart rate is], and yet despite that, quite a lot of people can do it." (Take a heart quiz.)

Playing the card game then showed that people who counted their own heartbeats more accurately caught on to the stacked decks much quicker—even if they didn't know it.

These participants said they weren't aware that certain decks were rigged even after a hundred trials, long after their actions showed they had subconsciously figured it out.

However, about one in four subjects' bodies betrayed him or her: "The signals were completely switched over," Dunn said.

Those test subjects' heart rates increased when they were about to pull from the "good" decks. Among these people, players who were also very accurate at counting their own heartbeats caught on to the ruse slowly, if at all.

That makes intuition a "mixed blessing," the researchers said.

"Knowing when to trust and when to discount such 'gut feelings' may relate to the extent to which individuals ... make optimal choices at crucial junctures in life," the study authors write.