I'm a psychologist who helped cast 'Survivor' for years. I weeded out people who might be dangerous or unstable under pressure — here's what I looked for in contestants.

• Dr. Ronald Stolberg is a psychologist who used to work for the reality television show "Survivor."
• Stolberg worked during applicant screening and the game, helping players handle the stress.

This as-told-to essay is based on a conversation with Dr. Ronald Stolberg, a former psychologist for the reality television show "Survivor." It has been edited for length and clarity.

Survivor producer Mark Burnett paired with clinical psychologist Richard Levak to design a psychological screening program for "Survivor," and then most of the other reality TV shows too. That's where psychology got its toehold in reality TV. Levak traveled with the show and screened the contestants.

When "Survivor" became a top show on network TV and Levak couldn't handle all the work himself, he started offering other psychologists a spot. By 2009, I guess it was my turn.

Shows like 'Survivor' have thousands of applicants to sort through

They have production assistants who go through all of them and cut 100,000 videos down to 1,000 videos. Then, the higher ups start looking at those videos. They'll narrow it down to somewhere between 50 and 100 people they think would be a good fit for their season.

At this point, the potential contestants have gone through several interviews. They really put through the wringer to see if they'd be good on the show.

The producers want to meet everyone in person. They get a lot of paperwork signed and review legal history, financial history, and medical history. Then, there's the psychological side.

During casting, the psychologist looks at applicants' personalities and the stability of their psyches

We would use a number of psychological measures to get data about the people. We would conduct interviews and do lots of observations of them running around and talking to people. Through this, we get a really good sense for who they are.

The role of the psychologist at that point is to screen out folks who might be dangerous, or folks who might be susceptible to becoming traumatized, anxious, depressed. It's not fun to watch people have an existential crisis on TV. We also screened out people we thought we didn't have a good feel for.

The screening, in part, is to craft a message for the producers that shows what the person's going to be like on the show. Are they going to take chances? Are they going to form alliances? Are they going to be deceitful? Are they going to be fun to watch on TV?

After everyone is cast, the psychologist on location prepares everybody for the game

It was a remarkable experience to fly with a television show, go on location in a jungle, and really be there for the contestants to make sure they're in good spirits.

When someone loses, they're disappointed and angry that they're out of a game and just lost $1 million. It's important to have someone there in case the contestant is more stressed than we hoped.

Hopefully, though, we did a good job screening players and selected people who were there for the right reasons: to experience something and to push themselves outside their comfort zone.

In my opinion, good 'Survivor' contestants have enough energy to be interesting and exciting on TV

It's not exciting to watch somebody who is fatigued and needs to lay down and rest the whole time. No. 2 would be a sense of adventure: taking chances, being risky, doing things a little bit outside their character. A really great contestant is one who reflects on their behavior during the show.

Being on any reality TV show is something you can't prepare for. There are dozens of camera people; the pressure, the tension, the paranoia of people talking about you, and thinking: "What's it going to look like on TV? What's my cut going to be?" It's a lot of pressure that people don't anticipate.

When screening for a reality TV show, I try to find people who are really genuine

What we get a lot of is people thinking they know what the show wants. People think, "They want a bad boy, they want drama, they want big moves, they want an instigator."

But if that's not true to their character, then that's not how they're going to play the show. People will revert back to their basic personality characteristics when put under stress.

I've made lifetime friendships with the people who were on the show

I've watched proposals happen at the airport when we came home from filming. "Survivor" changes people's lives. While contestants are gone, they realize: "Boy, am I silly. The best thing in my whole life is this person," and they come home and propose.

I've been to weddings, I've met people's babies, I've gone to sporting events with a big group of people during a reunion. It's really nice that contestants feel like they have support and people who understand what they went through. It's one of the reasons people on the show tend to become friends.

It's really hard to explain what the pressure and tension of being on a reality show is like, especially one where you travel to a foreign country and are isolated for almost two months.

Working for a show like 'Survivor' is such an honor and pleasure

It's lucrative, but really difficult to do if you have another job. That's why it wasn't a great fit for me. I have a faculty position and a private practice where I see patients. I essentially was gone for four months when I was working on the show.

The hardest part was getting a voicemail or a text that said, "Dr. Stolberg, we need you in LA this evening. We've brought in a few more contestants we'd like you to screen." I would be like: "It's my mom's birthday," or "I'm seeing patients this afternoon." The expectation was: "If you want this job, you have to jump when we say jump."

I think that's why there's a small group of people who can make their living doing this. I've declined other opportunities because they interfere too much with a regular job and family.