Lizzy Caplan and Michael Sheen on 'Masters of Sex'

Showtime's hit Sunday night series "Masters of Sex" has brought new attention to the work of pioneering sex researchers Masters and Johnson. In their time -- the 1950s and 1960s, the idea of studying sexual intercourse scientifically was far more controversial than the idea of making a television series about it today. On Showtime, anything goes, and some of the sexual studies the pair filmed for research purposes are as graphic and tantalizing as any R-rated movie. By the end of the first season, these included ones with Masters and Johnson themselves.

Season One introduced audiences to William Masters and Virginia Johnson, played by Michael Sheen and Lizzy Caplan. He is a gynecologist interested in making a clinical study of human sexual response; she is the woman he hired as his research assistant. By the end of the season, their work is being discredited as being prurient; but as Season Two began, their study is back on track, this time at a new, though less prestigious, hospital.

Controversial theories

While they expected criticism for their work, one thing they didn't expect was the sexual harassment Johnson experienced from Masters' medical colleagues who had seen her in the clinical footage. For Caplan playing Johnson illuminated the issues women face, then and now.

"I don't think they're limited to that time at all," Caplan told the Television Critics Association earlier this summer. "It's a question that I've asked myself quite a bit more since becoming a part of this show. Gender inequality is not something that's relegated to the 1950s, not at all. If anything, doing this show has pointed out how far we have left to go on a daily basis and, especially, in this business. Virginia is a woman who owns her own sexuality, and has career goals and ambitions outside of being somebody's wife and a stay at home mom."

This puts her outside the mainstream with other women in the conformist 1950s. "She's not exactly welcomed with open arms by them, so gets it from all sides."

Masters and Johnson began their study at a time when sexuality was not discussed publicly. (For instance Masters learned for himself about women's tendency to fake orgasms, something we take for granted today.) While their research would ultimately inform sexual progress, not everything Masters and Johnson did would be considered progressive today.

"Unfortunately their names are tied to homosexual conversion therapies, which is something that they started getting into much later in their career," Caplan said, referring to this controversial aspect of their work. "It's something that Virginia never believed in and never stood behind."

About conversion therapy

In the series Masters counsels his friend Barton Scully (Beau Bridges) against electroshock treatments to "cure" his homosexuality, which was graphically presented on an early episode in the second season.

"He (Masters) wasn't making any judgment on homosexuals," Caplan continued. "If anything, he was trying to help people. That's what they were always trying to do. You see it with Beau Bridges' character. Bill Masters is not anti-homosexuality, he wants to help his friend. In order to help his friend, he needs to help him not be gay anymore. These are ideas that can feel old, but I think everybody's well aware that they're not old at all. You hear kids struggling with these issues today. It doesn't feel like it's 1959; it feels like 2014 and these kids are still being persecuted."

The discredited practices of Conversion Therapy hit home for Caplan. "I have some friends who were sent to gay conversion camps," she shared. "It's the same. And then what's going on with transgender kids and the bullying around that. If anything, those conversations have reached more of a fever pitch now, but it's the same issue that's nowhere near resolved."

Kickstarted the sexual revolution

As their study continues, Sheen sees how integral Masters becomes in the cultural and social revolution bubbling to the surface in the 1960s. "This season we're interested in exploring the margins of society, especially because Masters has been kicked out of the mainstream in a way. He's dealing with an area that is certainly in the margins. His study is not an accepted norm. So now that he's lost his respectability, in terms of working for the hospital, he has to go and be in areas that he's not as comfortable with. He has to be in those margins. The people that he comes up against, the people that he rubs shoulders with, are maybe more representative of some things that will become more mainstream, such as the Civil Rights movement which moved from the margins to being reported on the front pages of newspapers."

"They kicked off the sexual revolution," Caplan added.

It was a change that Johnson, who was comfortable with sexuality, found easier to navigate than Masters. "All of a sudden, this (sexuality) became an asset for the first time in her life," she observed. For Masters, change was more complicated.

"What I find interesting in a way is that while he is very much a product of his culture, he's also part of the work that is going to change that culture," Sheen said. "He will, in turn, be changed by that culture, so there's a very interesting process going on. For a man who is so closed in so many ways, so frightened of vulnerability and intimacy, for him to keep studying something that inevitably always leads back to intimacy, exposure, vulnerability in some way, that's good drama. I find that fascinating."

Finding their characters

One book that proved invaluable for the actors in better understanding their characters lives and times is Thomas Maier's biography "Masters of Sex: The Life and Times of William Masters and Virginia Johnson, the Couple Who Taught America How to Love," from which the series is based.

"I've been involved with this project for about three years now and my feelings toward some of Virginia's choices obviously have begun to evolve,' 'Caplan said. "But it's my job to be the custodian of this person's story in this show. My job is not to judge things that she does, rather to justify them. To make them make sense so that I can play each moment authentically. Even though Virginia does do some questionable things, in her mind she's justified every step of the way."

Sheen, on the other hand, put down the book once filming began. "To begin with I sort of read pretty much everything there was to read and looked at everything," he said. "Then I felt like I got the sense of who this man is that I'm going to play, and then I've sort of done less and less [research]. It's not like I go back and keep checking. I now play the character I play and that's who I'm playing. I'll just go back now and again and remind myself of what began the trajectory for me."

"Masters of Sex" continues Sunday nights through September 28, 2014 on Showtime.