The time-hallowed institution known as the celebrity interview seems ready for the endangered list. With stars growing ever more wary of the media, last week’s imbroglio involving Brett Ratner underscored yet again the hazards of any misstep at a time of political correctness.

Only during awards season do stars dare to share a stray moment of candor. It was refreshing last week to hear the ever-cautious Leonardo DiCaprio critique opposition to gay marriage or to learn Clint Eastwood’s rejection of the “personhood” movement — “Don’t give me that sanctity crap.”

The publication of a memoir can also bring down the walls of caution. In “Then Again,” the famously private Diane Keaton reveals her “highlight reel” of past lovers: She found Warren Beatty “romantic and very kind” but she was blown away by her first Mel Gibson kiss and ultimately decided that Al Pacino was “the love of my life.” On the other hand, her discussion of Woody Allen is more anatomically detailed — “I loved his body; he is beautiful.”

OK, that’s what memoirs are all about. But for Keaton to discuss her romantic past comes as a surprise. During her previous interviews, when asked about Beatty, she would usually ask, “Warren who?” At age 65, Keaton, a truly gracious person, is bringing up two kids as a single mother and clearly relishing her new writing career.

Tom Hanks, another veteran of the interview circuit, probably would not match her candor. He went so far as to write a survival guide for fellow stars, which appeared in Entertainment Weekly. Calling the circuit “the celebrity mule train,” Hanks recommends that colleagues “prepare a set of obvious answers” that can be recited at least 30 times in a given day. It’s OK to introduce small variations, says Hanks, but stars must stay on message and must keep telling themselves, “You can do this for a few more days, can’t you?”

The Hanks mandate may make sense today, but it would have seemed alien to the stars of a generation ago. I did my first “star interviews” back in the ’60s (I was newly arrived in town as a reporter for the New York Times and didn’t know better) and, sorting through my old clips recently, I was surprised at the candor displayed by celebrities of that era.

Cary Grant, during one meeting, gave me a half-hour lecture on the pleasures of dropping acid. Walter Matthau informed me he wouldn’t even start talking unless I promised to describe him in print as “the Ukrainian Gary Grant.” Paul Newman, when asked about his latest movie, responded: “Why talk about Hollywood crap when we should be talking about Vietnam?” We did.

Natalie Wood, having just finished shooting a movie, complained “I’ve made 40 movies in 22 years starting from the age of 5, and no one has ever given me the chance to get a decent education.” She said she wanted only to chat about the author she was now reading, T.S. Eliot (I panicked, having dozed through my only Eliot lecture). Steve McQueen, who was under instruction by the studio to sing the glories of “Sand Pebbles,” which had been shot in Taiwan, instead ranted, “Anything I ever did wrong in life, I paid for on Taiwan. The baddest bad scene ever.”

If stars often refused to stay on message, the corporate icons of the day could be equally rebellious. Seated in his commissary, Walt Disney said that his chief of publicity wanted him only to talk about Disneyland, but he wearily told me, “I like to say what’s on my mind.” He continued: “People are trying to push me into making Don Quixote, but I don’t want to. I figure we’ll be crucified in the Latin countries if we don’t get it right. I got trapped into Alice in Wonderland against my better judgment and it was a terrible disappointment. I loved the illustrations in the book, but I never exactly died laughing over the story. It’s tough to translate whimsy to the screen.”

Walt’s conclusion: “I do best sticking to my own instincts and my own stories.”

He apologized if he seemed grumpy. “Can I give you my personal tour of Disneyland?” he asked.

I had a tough time thinking it over before accepting.

None of today’s studio chiefs would speak with Walt’s blunt candor. I even doubt if any would offer a tour. n Peter Bart