CBS Entertainment President Glenn Geller repeatedly promised to "do better" to fix the network's diversity issues after being put on the hot seat Wednesday at the Television Critics Association fall previews.

"We're really mindful at CBS about the importance of diversity and inclusion," Geller said. "We need to do better and we know it. That's really it."

CBS doesn't have a great track record of diversity in front of or behind the camera. All of its new fall shows feature white male leads — including Michael Weatherly, Matt LeBlanc, Kevin James and Joel McHale, and all of those series' showrunners are male as well. Geller acknowledged that none of his series leads are diverse, but stressed that 11 of 16 supporting roles this season are diverse. ("I know they're not leads," he acknowledged.) He also said that CBS has more LGBT characters this year, including Laverne Cox's lawyer on Doubt — the first transgender series regular played by a transgender actress on broadcast TV.

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"In terms of leads, we are definitely less diverse this year than last year's," he said. "In terms of overall diversity ... we were actually more diverse this year than last year and I think that's our commitment to diversity. It is ongoing. ... 11 of our series regulars are diverse. ... Those aren't just words. That's real action. I understand certainly the inclination to look at the screen and just look at leads and say, 'What's going on?' [But] we also have to look behind the camera. There, we're doing very well. Our writers are more diverse than last year. Our writers are more diverse. We continue to put more additional resources and financial support into our CBS Diversity Institute."

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Geller's words felt a bit hollow a day after FX Networks President John Landgraf revealed that he cut his network's diversity issues in half in less than a year. Geller had already said in January that he wanted CBS to do better. Pressed for a more clear commitment to change, Geller said, "I'm acknowledging we need to do better. In terms of directors, we've been getting better and better every year about directors among our director ranks. ... This year on Madam Secretary and The Odd Couple, over half the directors are diverse. ... I hear you. I understand that we need to do better. I do want to point out that in ensemble casting, we are more diverse than last year."

Here are other highlights from the panel:

- More Big Bang Theory: Geller isn't worried about losing CBS' biggest moneymaker after Season 10 this year. "We are very confident that everyone involved wants more Big Bang past year 10 and I know Warner Bros. will make those deals," he said.

-Limitless' cancellation: Geller said the bubble show's fate could've gone either way, but ultimately, "I don't think it connected with viewers."

- Summer series: Will BrainDead or American Gothic be back? "We haven't made any determination on any of the other scripted shows this summer," Geller said. Zoo, on the other hand, has been renewed for Season 3.

- Superhero shows: CBS shuffled Supergirl off to sister network CW for Season 2, but Geller said the network is certainly open to other superhero projects in the future. "If we heard the right superhero pitch and we thought it's for us, we'd absolutely buy it," he said. "No one has said, 'We have the right show for you' [yet]."

-Big Brother's bad behavior: While Season 18's misogyny and mean girl-ness isn't as bad as Season 15's racism, it certainly isn't becoming. Geller did not defend any of the houseguests' behavior, but chalked it up to the show being a social experiment. "[Casting directors] do the best they can to look into people's backgrounds ... but that's what's so great about the show," he said. "When you put people together, they become who they are. ... Yes, there are always going to be tensions and issues. But that's what the show is about. It's a social experiment."

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