William Petersen On Real Gil Grissom

(CBS)  The man in charge at "CSI" has a big heart, but would rather people think he has a big brain, says the actor who plays him.

During "CSI Week" on The Early Show Thursday, William Petersen

revealed some juicy morsels

to co-anchor Julie Chen about who his character, the mysterious Gil Grissom, really is.

On the show, Grissom stays cool and calm as he solves the toughest cases, while keeping much of his own personality under wraps.

But Petersen says there's a lot more to the lead investigator on "CSI" than you might think.

"I think it all, for him, is some sort of a study," Grissom observed to Chen. "He knows what he can and can't handle.

"I think he has a big heart. I don't think he would do what he does if he didn't have a big heart. He likes to pretend he has a big brain instead."

Pressed on that by Chen, Petersen pointed out: "I didn't say which one was bigger. … I'm just saying that Grissom would prefer you to think that his brain was bigger. It makes it easier for him."

So, Chen remarked, he is human?

"Probably," Petersen smiled.

After six years of getting up close and personal with murder and its aftermath, Chen noted, Petersen seems to understand what real "CSIs" also know: bottom line, it's just a job.

Said Petersen: "What happens over the course of time is that, you know, the more you see, the more you get used to it. I mean, it, it's true of the real CSIs, and policemen, and such like that, and I think that's also true of us at a certain point. You know … we do it all the time. ... You know, day in and day out, not just Thursday nights, you know, so, uh, maybe we're a little more inured to it."

Petersen says scripts in which the victims are children bother him, adding, "Those are usually the thing, the ones that are most disturbing for me."

Petersen also said: "One of the things about this show is that, you know, it happens. Uh, we come on the show after the bad thing has happened. And we rebuild it, on some level. And, so, it makes it more tolerable. … So, there's a perspective to it, which is, I think, helpful, not only to our audience, but also to our actors."