Inside the Rigorous Vetting Process for 'Married at First Sight' Season 4

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ET got a look at how producers made sure the participants' hearts were in the right place for season four of Married at First Sight.

The premise of the reality show is simple: two strangers get married the very first time they meet. As one might imagine, this presents a risk of one of the participants having ulterior motives for appearing on the show. Relationship expert Rachel DeAlto explains how they went about protecting the integrity of the show in a behind-the-scenes clip.

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"Each candidate goes through a very thorough background check to determine if they have significant debts or any sort of criminal record," DeAlto says in a clip.

One of the show's marriage counselors, Pastor Calvin Roberson, adds that participants' mental and moral states are also up for evaluation.

"We're looking at things like their psychological testing, their core values," Roberson says. "These are legally binding marriages. Annulment is not an option."

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Six participants (Heather Seidel, Lillian Vilchez, Sonia Granados, Derek Schwartz, Nick Pendergrast and Tom Wilson) were chosen this season out of more than 30,000 applicants. While they all seem to think they have a shot at love, the cold, hard numbers reveal that out of 18 past participants, only two couples have stayed together. Still, this new crop of hopefuls is not discouraged.

"I'm going to give it 100 percent!" Sonia told ET.

"I think keeping that mindset is something that will keep me more motivated," said Tom.

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Married at First Sight returns to FYI on July 26 at 8 p.m. ET/PT.